Rockchip RK3399 - DRM encoder、bridge、connector基础知识
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开发板 ：NanoPC-T4开发板
eMMC ：16GB
LPDDR3 ：4GB
显示屏 ：15.6英寸HDMI接口显示屏
u-boot ：2023.04
linux ：6.3
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一、encoder数据结构
1.1 struct drm_encoder
linux内核使用struct drm_encoder来表示一个编码器，将crtc输出的图像信号转换成一定格式的数字信号，如HDMI、DisplayPort、MIPI等；定义在include/drm/drm_encoder.h:
/**
* struct drm_encoder - central DRM encoder structure
* @dev: parent DRM device
* @head: list management
* @base: base KMS object
* @name: human readable name, can be overwritten by the driver
* @funcs: control functions, can be NULL for simple managed encoders
* @helper_private: mid-layer private data
*
* CRTCs drive pixels to encoders, which convert them into signals
* appropriate for a given connector or set of connectors.
*/
struct drm_encoder {
struct drm_device *dev;
struct list_head head;
struct drm_mode_object base;
char *name;
/**
* @encoder_type:
*
* One of the DRM_MODE_ENCODER_<foo> types in drm_mode.h. The following
* encoder types are defined thus far:
*
* - DRM_MODE_ENCODER_DAC for VGA and analog on DVI-I/DVI-A.
*
* - DRM_MODE_ENCODER_TMDS for DVI, HDMI and (embedded) DisplayPort.
*
* - DRM_MODE_ENCODER_LVDS for display panels, or in general any panel
* with a proprietary parallel connector.
*
* - DRM_MODE_ENCODER_TVDAC for TV output (Composite, S-Video,
* Component, SCART).
*
* - DRM_MODE_ENCODER_VIRTUAL for virtual machine displays
*
* - DRM_MODE_ENCODER_DSI for panels connected using the DSI serial bus.
*
* - DRM_MODE_ENCODER_DPI for panels connected using the DPI parallel
* bus.
*
* - DRM_MODE_ENCODER_DPMST for special fake encoders used to allow
* mutliple DP MST streams to share one physical encoder.
*/
int encoder_type;
/**
* @index: Position inside the mode_config.list, can be used as an array
* index. It is invariant over the lifetime of the encoder.
*/
unsigned index;
/**
* @possible_crtcs: Bitmask of potential CRTC bindings, using
* drm_crtc_index() as the index into the bitfield. The driver must set
* the bits for all &drm_crtc objects this encoder can be connected to
* before calling drm_dev_register().
*
* You will get a WARN if you get this wrong in the driver.
*
* Note that since CRTC objects can't be hotplugged the assigned indices
* are stable and hence known before registering all objects.
*/
uint32_t possible_crtcs;
/**
* @possible_clones: Bitmask of potential sibling encoders for cloning,
* using drm_encoder_index() as the index into the bitfield. The driver
* must set the bits for all &drm_encoder objects which can clone a
* &drm_crtc together with this encoder before calling
* drm_dev_register(). Drivers should set the bit representing the
* encoder itself, too. Cloning bits should be set such that when two
* encoders can be used in a cloned configuration, they both should have
* each another bits set.
*
* As an exception to the above rule if the driver doesn't implement
* any cloning it can leave @possible_clones set to 0. The core will
* automagically fix this up by setting the bit for the encoder itself.
*
* You will get a WARN if you get this wrong in the driver.
*
* Note that since encoder objects can't be hotplugged the assigned indices
* are stable and hence known before registering all objects.
*/
uint32_t possible_clones;
/**
* @crtc: Currently bound CRTC, only really meaningful for non-atomic
* drivers. Atomic drivers should instead check
* &drm_connector_state.crtc.
*/
struct drm_crtc *crtc;
/**
* @bridge_chain: Bridges attached to this encoder. Drivers shall not
* access this field directly.
*/
struct list_head bridge_chain;
const struct drm_encoder_funcs *funcs;
const struct drm_encoder_helper_funcs *helper_private;
};
1.2 操作函数
1.2.1 struct drm_encoder_funcs
struct drm_encoder_funcs用于描述encoder的控制函数，定义在include/drm/drm_encoder.h；
/**
* struct drm_encoder_funcs - encoder controls
*
* Encoders sit between CRTCs and connectors.
*/
struct drm_encoder_funcs {
/**
* @reset:
*
* Reset encoder hardware and software state to off. This function isn't
* called by the core directly, only through drm_mode_config_reset().
* It's not a helper hook only for historical reasons.
*/
void (*reset)(struct drm_encoder *encoder);
/**
* @destroy:
*
* Clean up encoder resources. This is only called at driver unload time
* through drm_mode_config_cleanup() since an encoder cannot be
* hotplugged in DRM.
*/
void (*destroy)(struct drm_encoder *encoder);
/**
* @late_register:
*
* This optional hook can be used to register additional userspace
* interfaces attached to the encoder like debugfs interfaces.
* It is called late in the driver load sequence from drm_dev_register().
* Everything added from this callback should be unregistered in
* the early_unregister callback.
*
* Returns:
*
* 0 on success, or a negative error code on failure.
*/
int (*late_register)(struct drm_encoder *encoder);
/**
* @early_unregister:
*
* This optional hook should be used to unregister the additional
* userspace interfaces attached to the encoder from
* @late_register. It is called from drm_dev_unregister(),
* early in the driver unload sequence to disable userspace access
* before data structures are torndown.
*/
void (*early_unregister)(struct drm_encoder *encoder);
};
1.2.2 struct drm_encoder_helper_funcs
struct drm_encoder_helper_funcs定义了一些常用的encoder辅助操作函数，定义在include/drm/drm_modeset_helper_vtables.h；
点击查看代码
/**
* struct drm_encoder_helper_funcs - helper operations for encoders
*
* These hooks are used by the legacy CRTC helpers, the transitional plane
* helpers and the new atomic modesetting helpers.
*/
struct drm_encoder_helper_funcs {
/**
* @dpms:
*
* Callback to control power levels on the encoder. If the mode passed in
* is unsupported, the provider must use the next lowest power level.
* This is used by the legacy encoder helpers to implement DPMS
* functionality in drm_helper_connector_dpms().
*
* This callback is also used to disable an encoder by calling it with
* DRM_MODE_DPMS_OFF if the @disable hook isn't used.
*
* This callback is used by the legacy CRTC helpers. Atomic helpers
* also support using this hook for enabling and disabling an encoder to
* facilitate transitions to atomic, but it is deprecated. Instead
* @enable and @disable should be used.
*/
void (*dpms)(struct drm_encoder *encoder, int mode);
/**
* @mode_valid:
*
* This callback is used to check if a specific mode is valid in this
* encoder. This should be implemented if the encoder has some sort
* of restriction in the modes it can display. For example, a given
* encoder may be responsible to set a clock value. If the clock can
* not produce all the values for the available modes then this callback
* can be used to restrict the number of modes to only the ones that
* can be displayed.
*
* This hook is used by the probe helpers to filter the mode list in
* drm_helper_probe_single_connector_modes(), and it is used by the
* atomic helpers to validate modes supplied by userspace in
* drm_atomic_helper_check_modeset().
*
* This function is optional.
*
* NOTE:
*
* Since this function is both called from the check phase of an atomic
* commit, and the mode validation in the probe paths it is not allowed
* to look at anything else but the passed-in mode, and validate it
* against configuration-invariant hardward constraints. Any further
* limits which depend upon the configuration can only be checked in
* @mode_fixup or @atomic_check.
*
* RETURNS:
*
* drm_mode_status Enum
*/
enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc,
const struct drm_display_mode *mode);
/**
* @mode_fixup:
*
* This callback is used to validate and adjust a mode. The parameter
* mode is the display mode that should be fed to the next element in
* the display chain, either the final &drm_connector or a &drm_bridge.
* The parameter adjusted_mode is the input mode the encoder requires. It
* can be modified by this callback and does not need to match mode. See
* also &drm_crtc_state.adjusted_mode for more details.
*
* This function is used by both legacy CRTC helpers and atomic helpers.
* This hook is optional.
*
* NOTE:
*
* This function is called in the check phase of atomic modesets, which
* can be aborted for any reason (including on userspace's request to
* just check whether a configuration would be possible). Atomic drivers
* MUST NOT touch any persistent state (hardware or software) or data
* structures except the passed in adjusted_mode parameter.
*
* This is in contrast to the legacy CRTC helpers where this was
* allowed.
*
* Atomic drivers which need to inspect and adjust more state should
* instead use the @atomic_check callback. If @atomic_check is used,
* this hook isn't called since @atomic_check allows a strict superset
* of the functionality of @mode_fixup.
*
* Also beware that userspace can request its own custom modes, neither
* core nor helpers filter modes to the list of probe modes reported by
* the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
* that modes are filtered consistently put any encoder constraints and
* limits checks into @mode_valid.
*
* RETURNS:
*
* True if an acceptable configuration is possible, false if the modeset
* operation should be rejected.
*/
bool (*mode_fixup)(struct drm_encoder *encoder,
const struct drm_display_mode *mode,
struct drm_display_mode *adjusted_mode);
/**
* @prepare:
*
* This callback should prepare the encoder for a subsequent modeset,
* which in practice means the driver should disable the encoder if it
* is running. Most drivers ended up implementing this by calling their
* @dpms hook with DRM_MODE_DPMS_OFF.
*
* This callback is used by the legacy CRTC helpers. Atomic helpers
* also support using this hook for disabling an encoder to facilitate
* transitions to atomic, but it is deprecated. Instead @disable should
* be used.
*/
void (*prepare)(struct drm_encoder *encoder);
/**
* @commit:
*
* This callback should commit the new mode on the encoder after a modeset,
* which in practice means the driver should enable the encoder. Most
* drivers ended up implementing this by calling their @dpms hook with
* DRM_MODE_DPMS_ON.
*
* This callback is used by the legacy CRTC helpers. Atomic helpers
* also support using this hook for enabling an encoder to facilitate
* transitions to atomic, but it is deprecated. Instead @enable should
* be used.
*/
void (*commit)(struct drm_encoder *encoder);
/**
* @mode_set:
*
* This callback is used to update the display mode of an encoder.
*
* Note that the display pipe is completely off when this function is
* called. Drivers which need hardware to be running before they program
* the new display mode (because they implement runtime PM) should not
* use this hook, because the helper library calls it only once and not
* every time the display pipeline is suspend using either DPMS or the
* new "ACTIVE" property. Such drivers should instead move all their
* encoder setup into the @enable callback.
*
* This callback is used both by the legacy CRTC helpers and the atomic
* modeset helpers. It is optional in the atomic helpers.
*
* NOTE:
*
* If the driver uses the atomic modeset helpers and needs to inspect
* the connector state or connector display info during mode setting,
* @atomic_mode_set can be used instead.
*/
void (*mode_set)(struct drm_encoder *encoder,
struct drm_display_mode *mode,
struct drm_display_mode *adjusted_mode);
/**
* @atomic_mode_set:
*
* This callback is used to update the display mode of an encoder.
*
* Note that the display pipe is completely off when this function is
* called. Drivers which need hardware to be running before they program
* the new display mode (because they implement runtime PM) should not
* use this hook, because the helper library calls it only once and not
* every time the display pipeline is suspended using either DPMS or the
* new "ACTIVE" property. Such drivers should instead move all their
* encoder setup into the @enable callback.
*
* This callback is used by the atomic modeset helpers in place of the
* @mode_set callback, if set by the driver. It is optional and should
* be used instead of @mode_set if the driver needs to inspect the
* connector state or display info, since there is no direct way to
* go from the encoder to the current connector.
*/
void (*atomic_mode_set)(struct drm_encoder *encoder,
struct drm_crtc_state *crtc_state,
struct drm_connector_state *conn_state);
/**
* @detect:
*
* This callback can be used by drivers who want to do detection on the
* encoder object instead of in connector functions.
*
* It is not used by any helper and therefore has purely driver-specific
* semantics. New drivers shouldn't use this and instead just implement
* their own private callbacks.
*
* FIXME:
*
* This should just be converted into a pile of driver vfuncs.
* Currently radeon, amdgpu and nouveau are using it.
*/
enum drm_connector_status (*detect)(struct drm_encoder *encoder,
struct drm_connector *connector);
/**
* @atomic_disable:
*
* This callback should be used to disable the encoder. With the atomic
* drivers it is called before this encoder's CRTC has been shut off
* using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
* sequence is too simple drivers can just add their own driver private
* encoder hooks and call them from CRTC's callback by looping over all
* encoders connected to it using for_each_encoder_on_crtc().
*
* This callback is a variant of @disable that provides the atomic state
* to the driver. If @atomic_disable is implemented, @disable is not
* called by the helpers.
*
* This hook is only used by atomic helpers. Atomic drivers don't need
* to implement it if there's no need to disable anything at the encoder
* level. To ensure that runtime PM handling (using either DPMS or the
* new "ACTIVE" property) works @atomic_disable must be the inverse of
* @atomic_enable.
*/
void (*atomic_disable)(struct drm_encoder *encoder,
struct drm_atomic_state *state);
/**
* @atomic_enable:
*
* This callback should be used to enable the encoder. It is called
* after this encoder's CRTC has been enabled using their own
* &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
* too simple drivers can just add their own driver private encoder
* hooks and call them from CRTC's callback by looping over all encoders
* connected to it using for_each_encoder_on_crtc().
*
* This callback is a variant of @enable that provides the atomic state
* to the driver. If @atomic_enable is implemented, @enable is not
* called by the helpers.
*
* This hook is only used by atomic helpers, it is the opposite of
* @atomic_disable. Atomic drivers don't need to implement it if there's
* no need to enable anything at the encoder level. To ensure that
* runtime PM handling works @atomic_enable must be the inverse of
* @atomic_disable.
*/
void (*atomic_enable)(struct drm_encoder *encoder,
struct drm_atomic_state *state);
/**
* @disable:
*
* This callback should be used to disable the encoder. With the atomic
* drivers it is called before this encoder's CRTC has been shut off
* using their own &drm_crtc_helper_funcs.disable hook. If that
* sequence is too simple drivers can just add their own driver private
* encoder hooks and call them from CRTC's callback by looping over all
* encoders connected to it using for_each_encoder_on_crtc().
*
* This hook is used both by legacy CRTC helpers and atomic helpers.
* Atomic drivers don't need to implement it if there's no need to
* disable anything at the encoder level. To ensure that runtime PM
* handling (using either DPMS or the new "ACTIVE" property) works
* @disable must be the inverse of @enable for atomic drivers.
*
* For atomic drivers also consider @atomic_disable and save yourself
* from having to read the NOTE below!
*
* NOTE:
*
* With legacy CRTC helpers there's a big semantic difference between
* @disable and other hooks (like @prepare or @dpms) used to shut down a
* encoder: @disable is only called when also logically disabling the
* display pipeline and needs to release any resources acquired in
* @mode_set (like shared PLLs, or again release pinned framebuffers).
*
* Therefore @disable must be the inverse of @mode_set plus @commit for
* drivers still using legacy CRTC helpers, which is different from the
* rules under atomic.
*/
void (*disable)(struct drm_encoder *encoder);
/**
* @enable:
*
* This callback should be used to enable the encoder. With the atomic
* drivers it is called after this encoder's CRTC has been enabled using
* their own &drm_crtc_helper_funcs.enable hook. If that sequence is
* too simple drivers can just add their own driver private encoder
* hooks and call them from CRTC's callback by looping over all encoders
* connected to it using for_each_encoder_on_crtc().
*
* This hook is only used by atomic helpers, it is the opposite of
* @disable. Atomic drivers don't need to implement it if there's no
* need to enable anything at the encoder level. To ensure that
* runtime PM handling (using either DPMS or the new "ACTIVE" property)
* works @enable must be the inverse of @disable for atomic drivers.
*/
void (*enable)(struct drm_encoder *encoder);
/**
* @atomic_check:
*
* This callback is used to validate encoder state for atomic drivers.
* Since the encoder is the object connecting the CRTC and connector it
* gets passed both states, to be able to validate interactions and
* update the CRTC to match what the encoder needs for the requested
* connector.
*
* Since this provides a strict superset of the functionality of
* @mode_fixup (the requested and adjusted modes are both available
* through the passed in &struct drm_crtc_state) @mode_fixup is not
* called when @atomic_check is implemented.
*
* This function is used by the atomic helpers, but it is optional.
*
* NOTE:
*
* This function is called in the check phase of an atomic update. The
* driver is not allowed to change anything outside of the free-standing
* state objects passed-in or assembled in the overall &drm_atomic_state
* update tracking structure.
*
* Also beware that userspace can request its own custom modes, neither
* core nor helpers filter modes to the list of probe modes reported by
* the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
* that modes are filtered consistently put any encoder constraints and
* limits checks into @mode_valid.
*
* RETURNS:
*
* 0 on success, -EINVAL if the state or the transition can't be
* supported, -ENOMEM on memory allocation failure and -EDEADLK if an
* attempt to obtain another state object ran into a &drm_modeset_lock
* deadlock.
*/
int (*atomic_check)(struct drm_encoder *encoder,
struct drm_crtc_state *crtc_state,
struct drm_connector_state *conn_state);
};
二、bridge数据结构
2.1 struct drm_bridge
linux内核使用struct drm_bridge来表示一个桥接设备，一般用于注册encoder后面另外再接的转换芯片；定义在include/drm/drm_bridge.h:
/**
* struct drm_bridge - central DRM bridge control structure
*/
struct drm_bridge {
/** @base: inherit from &drm_private_object */
struct drm_private_obj base;
/** @dev: DRM device this bridge belongs to */
struct drm_device *dev;
/** @encoder: encoder to which this bridge is connected */
struct drm_encoder *encoder;
/** @chain_node: used to form a bridge chain */
struct list_head chain_node;
#ifdef CONFIG_OF
/** @of_node: device node pointer to the bridge */
struct device_node *of_node;
#endif
/** @list: to keep track of all added bridges */
struct list_head list;
/**
* @timings:
*
* the timing specification for the bridge, if any (may be NULL)
*/
const struct drm_bridge_timings *timings;
/** @funcs: control functions */
const struct drm_bridge_funcs *funcs;
/** @driver_private: pointer to the bridge driver's internal context */
void *driver_private;
/** @ops: bitmask of operations supported by the bridge */
enum drm_bridge_ops ops;
/**
* @type: Type of the connection at the bridge output
* (DRM_MODE_CONNECTOR_*). For bridges at the end of this chain this
* identifies the type of connected display.
*/
int type;
/**
* @interlace_allowed: Indicate that the bridge can handle interlaced
* modes.
*/
bool interlace_allowed;
/**
* @pre_enable_prev_first: The bridge requires that the prev
* bridge @pre_enable function is called before its @pre_enable,
* and conversely for post_disable. This is most frequently a
* requirement for DSI devices which need the host to be initialised
* before the peripheral.
*/
bool pre_enable_prev_first;
/**
* @ddc: Associated I2C adapter for DDC access, if any.
*/
struct i2c_adapter *ddc;
/** private: */
/**
* @hpd_mutex: Protects the @hpd_cb and @hpd_data fields.
*/
struct mutex hpd_mutex;
/**
* @hpd_cb: Hot plug detection callback, registered with
* drm_bridge_hpd_enable().
*/
void (*hpd_cb)(void *data, enum drm_connector_status status);
/**
* @hpd_data: Private data passed to the Hot plug detection callback
* @hpd_cb.
*/
void *hpd_data;
};
2.2struct drm_bridge_funcs
struct drm_bridge_funcs用于描述bridge的控制函数，定义在include/drm/drm_bridge.h；
点击查看代码
/**
* struct drm_bridge_funcs - drm_bridge control functions
*/
struct drm_bridge_funcs {
/**
* @attach:
*
* This callback is invoked whenever our bridge is being attached to a
* &drm_encoder. The flags argument tunes the behaviour of the attach
* operation (see DRM_BRIDGE_ATTACH_*).
*
* The @attach callback is optional.
*
* RETURNS:
*
* Zero on success, error code on failure.
*/
int (*attach)(struct drm_bridge *bridge,
enum drm_bridge_attach_flags flags);
/**
* @detach:
*
* This callback is invoked whenever our bridge is being detached from a
* &drm_encoder.
*
* The @detach callback is optional.
*/
void (*detach)(struct drm_bridge *bridge);
/**
* @mode_valid:
*
* This callback is used to check if a specific mode is valid in this
* bridge. This should be implemented if the bridge has some sort of
* restriction in the modes it can display. For example, a given bridge
* may be responsible to set a clock value. If the clock can not
* produce all the values for the available modes then this callback
* can be used to restrict the number of modes to only the ones that
* can be displayed.
*
* This hook is used by the probe helpers to filter the mode list in
* drm_helper_probe_single_connector_modes(), and it is used by the
* atomic helpers to validate modes supplied by userspace in
* drm_atomic_helper_check_modeset().
*
* The @mode_valid callback is optional.
*
* NOTE:
*
* Since this function is both called from the check phase of an atomic
* commit, and the mode validation in the probe paths it is not allowed
* to look at anything else but the passed-in mode, and validate it
* against configuration-invariant hardward constraints. Any further
* limits which depend upon the configuration can only be checked in
* @mode_fixup.
*
* RETURNS:
*
* drm_mode_status Enum
*/
enum drm_mode_status (*mode_valid)(struct drm_bridge *bridge,
const struct drm_display_info *info,
const struct drm_display_mode *mode);
/**
* @mode_fixup:
*
* This callback is used to validate and adjust a mode. The parameter
* mode is the display mode that should be fed to the next element in
* the display chain, either the final &drm_connector or the next
* &drm_bridge. The parameter adjusted_mode is the input mode the bridge
* requires. It can be modified by this callback and does not need to
* match mode. See also &drm_crtc_state.adjusted_mode for more details.
*
* This is the only hook that allows a bridge to reject a modeset. If
* this function passes all other callbacks must succeed for this
* configuration.
*
* The mode_fixup callback is optional. &drm_bridge_funcs.mode_fixup()
* is not called when &drm_bridge_funcs.atomic_check() is implemented,
* so only one of them should be provided.
*
* NOTE:
*
* This function is called in the check phase of atomic modesets, which
* can be aborted for any reason (including on userspace's request to
* just check whether a configuration would be possible). Drivers MUST
* NOT touch any persistent state (hardware or software) or data
* structures except the passed in @state parameter.
*
* Also beware that userspace can request its own custom modes, neither
* core nor helpers filter modes to the list of probe modes reported by
* the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
* that modes are filtered consistently put any bridge constraints and
* limits checks into @mode_valid.
*
* RETURNS:
*
* True if an acceptable configuration is possible, false if the modeset
* operation should be rejected.
*/
bool (*mode_fixup)(struct drm_bridge *bridge,
const struct drm_display_mode *mode,
struct drm_display_mode *adjusted_mode);
/**
* @disable:
*
* This callback should disable the bridge. It is called right before
* the preceding element in the display pipe is disabled. If the
* preceding element is a bridge this means it's called before that
* bridge's @disable vfunc. If the preceding element is a &drm_encoder
* it's called right before the &drm_encoder_helper_funcs.disable,
* &drm_encoder_helper_funcs.prepare or &drm_encoder_helper_funcs.dpms
* hook.
*
* The bridge can assume that the display pipe (i.e. clocks and timing
* signals) feeding it is still running when this callback is called.
*
* The @disable callback is optional.
*
* NOTE:
*
* This is deprecated, do not use!
* New drivers shall use &drm_bridge_funcs.atomic_disable.
*/
void (*disable)(struct drm_bridge *bridge);
/**
* @post_disable:
*
* This callback should disable the bridge. It is called right after the
* preceding element in the display pipe is disabled. If the preceding
* element is a bridge this means it's called after that bridge's
* @post_disable function. If the preceding element is a &drm_encoder
* it's called right after the encoder's
* &drm_encoder_helper_funcs.disable, &drm_encoder_helper_funcs.prepare
* or &drm_encoder_helper_funcs.dpms hook.
*
* The bridge must assume that the display pipe (i.e. clocks and timing
* singals) feeding it is no longer running when this callback is
* called.
*
* The @post_disable callback is optional.
*
* NOTE:
*
* This is deprecated, do not use!
* New drivers shall use &drm_bridge_funcs.atomic_post_disable.
*/
void (*post_disable)(struct drm_bridge *bridge);
/**
* @mode_set:
*
* This callback should set the given mode on the bridge. It is called
* after the @mode_set callback for the preceding element in the display
* pipeline has been called already. If the bridge is the first element
* then this would be &drm_encoder_helper_funcs.mode_set. The display
* pipe (i.e. clocks and timing signals) is off when this function is
* called.
*
* The adjusted_mode parameter is the mode output by the CRTC for the
* first bridge in the chain. It can be different from the mode
* parameter that contains the desired mode for the connector at the end
* of the bridges chain, for instance when the first bridge in the chain
* performs scaling. The adjusted mode is mostly useful for the first
* bridge in the chain and is likely irrelevant for the other bridges.
*
* For atomic drivers the adjusted_mode is the mode stored in
* &drm_crtc_state.adjusted_mode.
*
* NOTE:
*
* This is deprecated, do not use!
* New drivers shall set their mode in the
* &drm_bridge_funcs.atomic_enable operation.
*/
void (*mode_set)(struct drm_bridge *bridge,
const struct drm_display_mode *mode,
const struct drm_display_mode *adjusted_mode);
/**
* @pre_enable:
*
* This callback should enable the bridge. It is called right before
* the preceding element in the display pipe is enabled. If the
* preceding element is a bridge this means it's called before that
* bridge's @pre_enable function. If the preceding element is a
* &drm_encoder it's called right before the encoder's
* &drm_encoder_helper_funcs.enable, &drm_encoder_helper_funcs.commit or
* &drm_encoder_helper_funcs.dpms hook.
*
* The display pipe (i.e. clocks and timing signals) feeding this bridge
* will not yet be running when this callback is called. The bridge must
* not enable the display link feeding the next bridge in the chain (if
* there is one) when this callback is called.
*
* The @pre_enable callback is optional.
*
* NOTE:
*
* This is deprecated, do not use!
* New drivers shall use &drm_bridge_funcs.atomic_pre_enable.
*/
void (*pre_enable)(struct drm_bridge *bridge);
/**
* @enable:
*
* This callback should enable the bridge. It is called right after
* the preceding element in the display pipe is enabled. If the
* preceding element is a bridge this means it's called after that
* bridge's @enable function. If the preceding element is a
* &drm_encoder it's called right after the encoder's
* &drm_encoder_helper_funcs.enable, &drm_encoder_helper_funcs.commit or
* &drm_encoder_helper_funcs.dpms hook.
*
* The bridge can assume that the display pipe (i.e. clocks and timing
* signals) feeding it is running when this callback is called. This
* callback must enable the display link feeding the next bridge in the
* chain if there is one.
*
* The @enable callback is optional.
*
* NOTE:
*
* This is deprecated, do not use!
* New drivers shall use &drm_bridge_funcs.atomic_enable.
*/
void (*enable)(struct drm_bridge *bridge);
/**
* @atomic_pre_enable:
*
* This callback should enable the bridge. It is called right before
* the preceding element in the display pipe is enabled. If the
* preceding element is a bridge this means it's called before that
* bridge's @atomic_pre_enable or @pre_enable function. If the preceding
* element is a &drm_encoder it's called right before the encoder's
* &drm_encoder_helper_funcs.atomic_enable hook.
*
* The display pipe (i.e. clocks and timing signals) feeding this bridge
* will not yet be running when this callback is called. The bridge must
* not enable the display link feeding the next bridge in the chain (if
* there is one) when this callback is called.
*
* The @atomic_pre_enable callback is optional.
*/
void (*atomic_pre_enable)(struct drm_bridge *bridge,
struct drm_bridge_state *old_bridge_state);
/**
* @atomic_enable:
*
* This callback should enable the bridge. It is called right after
* the preceding element in the display pipe is enabled. If the
* preceding element is a bridge this means it's called after that
* bridge's @atomic_enable or @enable function. If the preceding element
* is a &drm_encoder it's called right after the encoder's
* &drm_encoder_helper_funcs.atomic_enable hook.
*
* The bridge can assume that the display pipe (i.e. clocks and timing
* signals) feeding it is running when this callback is called. This
* callback must enable the display link feeding the next bridge in the
* chain if there is one.
*
* The @atomic_enable callback is optional.
*/
void (*atomic_enable)(struct drm_bridge *bridge,
struct drm_bridge_state *old_bridge_state);
/**
* @atomic_disable:
*
* This callback should disable the bridge. It is called right before
* the preceding element in the display pipe is disabled. If the
* preceding element is a bridge this means it's called before that
* bridge's @atomic_disable or @disable vfunc. If the preceding element
* is a &drm_encoder it's called right before the
* &drm_encoder_helper_funcs.atomic_disable hook.
*
* The bridge can assume that the display pipe (i.e. clocks and timing
* signals) feeding it is still running when this callback is called.
*
* The @atomic_disable callback is optional.
*/
void (*atomic_disable)(struct drm_bridge *bridge,
struct drm_bridge_state *old_bridge_state);
/**
* @atomic_post_disable:
*
* This callback should disable the bridge. It is called right after the
* preceding element in the display pipe is disabled. If the preceding
* element is a bridge this means it's called after that bridge's
* @atomic_post_disable or @post_disable function. If the preceding
* element is a &drm_encoder it's called right after the encoder's
* &drm_encoder_helper_funcs.atomic_disable hook.
*
* The bridge must assume that the display pipe (i.e. clocks and timing
* signals) feeding it is no longer running when this callback is
* called.
*
* The @atomic_post_disable callback is optional.
*/
void (*atomic_post_disable)(struct drm_bridge *bridge,
struct drm_bridge_state *old_bridge_state);
/**
* @atomic_duplicate_state:
*
* Duplicate the current bridge state object (which is guaranteed to be
* non-NULL).
*
* The atomic_duplicate_state hook is mandatory if the bridge
* implements any of the atomic hooks, and should be left unassigned
* otherwise. For bridges that don't subclass &drm_bridge_state, the
* drm_atomic_helper_bridge_duplicate_state() helper function shall be
* used to implement this hook.
*
* RETURNS:
* A valid drm_bridge_state object or NULL if the allocation fails.
*/
struct drm_bridge_state *(*atomic_duplicate_state)(struct drm_bridge *bridge);
/**
* @atomic_destroy_state:
*
* Destroy a bridge state object previously allocated by
* &drm_bridge_funcs.atomic_duplicate_state().
*
* The atomic_destroy_state hook is mandatory if the bridge implements
* any of the atomic hooks, and should be left unassigned otherwise.
* For bridges that don't subclass &drm_bridge_state, the
* drm_atomic_helper_bridge_destroy_state() helper function shall be
* used to implement this hook.
*/
void (*atomic_destroy_state)(struct drm_bridge *bridge,
struct drm_bridge_state *state);
/**
* @atomic_get_output_bus_fmts:
*
* Return the supported bus formats on the output end of a bridge.
* The returned array must be allocated with kmalloc() and will be
* freed by the caller. If the allocation fails, NULL should be
* returned. num_output_fmts must be set to the returned array size.
* Formats listed in the returned array should be listed in decreasing
* preference order (the core will try all formats until it finds one
* that works).
*
* This method is only called on the last element of the bridge chain
* as part of the bus format negotiation process that happens in
* &drm_atomic_bridge_chain_select_bus_fmts().
* This method is optional. When not implemented, the core will
* fall back to &drm_connector.display_info.bus_formats[0] if
* &drm_connector.display_info.num_bus_formats > 0,
* or to MEDIA_BUS_FMT_FIXED otherwise.
*/
u32 *(*atomic_get_output_bus_fmts)(struct drm_bridge *bridge,
struct drm_bridge_state *bridge_state,
struct drm_crtc_state *crtc_state,
struct drm_connector_state *conn_state,
unsigned int *num_output_fmts);
/**
* @atomic_get_input_bus_fmts:
*
* Return the supported bus formats on the input end of a bridge for
* a specific output bus format.
*
* The returned array must be allocated with kmalloc() and will be
* freed by the caller. If the allocation fails, NULL should be
* returned. num_input_fmts must be set to the returned array size.
* Formats listed in the returned array should be listed in decreasing
* preference order (the core will try all formats until it finds one
* that works). When the format is not supported NULL should be
* returned and num_input_fmts should be set to 0.
*
* This method is called on all elements of the bridge chain as part of
* the bus format negotiation process that happens in
* drm_atomic_bridge_chain_select_bus_fmts().
* This method is optional. When not implemented, the core will bypass
* bus format negotiation on this element of the bridge without
* failing, and the previous element in the chain will be passed
* MEDIA_BUS_FMT_FIXED as its output bus format.
*
* Bridge drivers that need to support being linked to bridges that are
* not supporting bus format negotiation should handle the
* output_fmt == MEDIA_BUS_FMT_FIXED case appropriately, by selecting a
* sensible default value or extracting this information from somewhere
* else (FW property, &drm_display_mode, &drm_display_info, ...)
*
* Note: Even if input format selection on the first bridge has no
* impact on the negotiation process (bus format negotiation stops once
* we reach the first element of the chain), drivers are expected to
* return accurate input formats as the input format may be used to
* configure the CRTC output appropriately.
*/
u32 *(*atomic_get_input_bus_fmts)(struct drm_bridge *bridge,
struct drm_bridge_state *bridge_state,
struct drm_crtc_state *crtc_state,
struct drm_connector_state *conn_state,
u32 output_fmt,
unsigned int *num_input_fmts);
/**
* @atomic_check:
*
* This method is responsible for checking bridge state correctness.
* It can also check the state of the surrounding components in chain
* to make sure the whole pipeline can work properly.
*
* &drm_bridge_funcs.atomic_check() hooks are called in reverse
* order (from the last to the first bridge).
*
* This method is optional. &drm_bridge_funcs.mode_fixup() is not
* called when &drm_bridge_funcs.atomic_check() is implemented, so only
* one of them should be provided.
*
* If drivers need to tweak &drm_bridge_state.input_bus_cfg.flags or
* &drm_bridge_state.output_bus_cfg.flags it should happen in
* this function. By default the &drm_bridge_state.output_bus_cfg.flags
* field is set to the next bridge
* &drm_bridge_state.input_bus_cfg.flags value or
* &drm_connector.display_info.bus_flags if the bridge is the last
* element in the chain.
*
* RETURNS:
* zero if the check passed, a negative error code otherwise.
*/
int (*atomic_check)(struct drm_bridge *bridge,
struct drm_bridge_state *bridge_state,
struct drm_crtc_state *crtc_state,
struct drm_connector_state *conn_state);
/**
* @atomic_reset:
*
* Reset the bridge to a predefined state (or retrieve its current
* state) and return a &drm_bridge_state object matching this state.
* This function is called at attach time.
*
* The atomic_reset hook is mandatory if the bridge implements any of
* the atomic hooks, and should be left unassigned otherwise. For
* bridges that don't subclass &drm_bridge_state, the
* drm_atomic_helper_bridge_reset() helper function shall be used to
* implement this hook.
*
* Note that the atomic_reset() semantics is not exactly matching the
* reset() semantics found on other components (connector, plane, ...).
*
* 1. The reset operation happens when the bridge is attached, not when
* drm_mode_config_reset() is called
* 2. It's meant to be used exclusively on bridges that have been
* converted to the ATOMIC API
*
* RETURNS:
* A valid drm_bridge_state object in case of success, an ERR_PTR()
* giving the reason of the failure otherwise.
*/
struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
/**
* @detect:
*
* Check if anything is attached to the bridge output.
*
* This callback is optional, if not implemented the bridge will be
* considered as always having a component attached to its output.
* Bridges that implement this callback shall set the
* DRM_BRIDGE_OP_DETECT flag in their &drm_bridge->ops.
*
* RETURNS:
*
* drm_connector_status indicating the bridge output status.
*/
enum drm_connector_status (*detect)(struct drm_bridge *bridge);
/**
* @get_modes:
*
* Fill all modes currently valid for the sink into the &drm_connector
* with drm_mode_probed_add().
*
* The @get_modes callback is mostly intended to support non-probeable
* displays such as many fixed panels. Bridges that support reading
* EDID shall leave @get_modes unimplemented and implement the
* &drm_bridge_funcs->get_edid callback instead.
*
* This callback is optional. Bridges that implement it shall set the
* DRM_BRIDGE_OP_MODES flag in their &drm_bridge->ops.
*
* The connector parameter shall be used for the sole purpose of
* filling modes, and shall not be stored internally by bridge drivers
* for future usage.
*
* RETURNS:
*
* The number of modes added by calling drm_mode_probed_add().
*/
int (*get_modes)(struct drm_bridge *bridge,
struct drm_connector *connector);
/**
* @get_edid:
*
* Read and parse the EDID data of the connected display.
*
* The @get_edid callback is the preferred way of reporting mode
* information for a display connected to the bridge output. Bridges
* that support reading EDID shall implement this callback and leave
* the @get_modes callback unimplemented.
*
* The caller of this operation shall first verify the output
* connection status and refrain from reading EDID from a disconnected
* output.
*
* This callback is optional. Bridges that implement it shall set the
* DRM_BRIDGE_OP_EDID flag in their &drm_bridge->ops.
*
* The connector parameter shall be used for the sole purpose of EDID
* retrieval and parsing, and shall not be stored internally by bridge
* drivers for future usage.
*
* RETURNS:
*
* An edid structure newly allocated with kmalloc() (or similar) on
* success, or NULL otherwise. The caller is responsible for freeing
* the returned edid structure with kfree().
*/
struct edid *(*get_edid)(struct drm_bridge *bridge,
struct drm_connector *connector);
/**
* @hpd_notify:
*
* Notify the bridge of hot plug detection.
*
* This callback is optional, it may be implemented by bridges that
* need to be notified of display connection or disconnection for
* internal reasons. One use case is to reset the internal state of CEC
* controllers for HDMI bridges.
*/
void (*hpd_notify)(struct drm_bridge *bridge,
enum drm_connector_status status);
/**
* @hpd_enable:
*
* Enable hot plug detection. From now on the bridge shall call
* drm_bridge_hpd_notify() each time a change is detected in the output
* connection status, until hot plug detection gets disabled with
* @hpd_disable.
*
* This callback is optional and shall only be implemented by bridges
* that support hot-plug notification without polling. Bridges that
* implement it shall also implement the @hpd_disable callback and set
* the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
*/
void (*hpd_enable)(struct drm_bridge *bridge);
/**
* @hpd_disable:
*
* Disable hot plug detection. Once this function returns the bridge
* shall not call drm_bridge_hpd_notify() when a change in the output
* connection status occurs.
*
* This callback is optional and shall only be implemented by bridges
* that support hot-plug notification without polling. Bridges that
* implement it shall also implement the @hpd_enable callback and set
* the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
*/
void (*hpd_disable)(struct drm_bridge *bridge);
/**
* @debugfs_init:
*
* Allows bridges to create bridge-specific debugfs files.
*/
void (*debugfs_init)(struct drm_bridge *bridge, struct dentry *root);
};
2.3 drm_bridge_attach
drm_bridge_attach定义在drivers/gpu/drm/drm_bridge.c,该函数的作用是将bridge连接到encoder的链中；
/**
* drm_bridge_attach - attach the bridge to an encoder's chain
*
* @encoder: DRM encoder
* @bridge: bridge to attach
* @previous: previous bridge in the chain (optional)
* @flags: DRM_BRIDGE_ATTACH_* flags
*
* Called by a kms driver to link the bridge to an encoder's chain. The previous
* argument specifies the previous bridge in the chain. If NULL, the bridge is
* linked directly at the encoder's output. Otherwise it is linked at the
* previous bridge's output.
*
* If non-NULL the previous bridge must be already attached by a call to this
* function.
*
* Note that bridges attached to encoders are auto-detached during encoder
* cleanup in drm_encoder_cleanup(), so drm_bridge_attach() should generally
* *not* be balanced with a drm_bridge_detach() in driver code.
*
* RETURNS:
* Zero on success, error code on failure
*/
int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
struct drm_bridge *previous,
enum drm_bridge_attach_flags flags)
{
int ret;
if (!encoder || !bridge)
return -EINVAL;
if (previous && (!previous->dev || previous->encoder != encoder))
return -EINVAL;
if (bridge->dev)
return -EBUSY;
bridge->dev = encoder->dev;
bridge->encoder = encoder;
if (previous)
list_add(&bridge->chain_node, &previous->chain_node);
else
list_add(&bridge->chain_node, &encoder->bridge_chain);
if (bridge->funcs->attach) {
ret = bridge->funcs->attach(bridge, flags);
if (ret < 0)
goto err_reset_bridge;
}
if (bridge->funcs->atomic_reset) {
struct drm_bridge_state *state;
state = bridge->funcs->atomic_reset(bridge);
if (IS_ERR(state)) {
ret = PTR_ERR(state);
goto err_detach_bridge;
}
drm_atomic_private_obj_init(bridge->dev, &bridge->base,
&state->base,
&drm_bridge_priv_state_funcs);
}
return 0;
err_detach_bridge:
if (bridge->funcs->detach)
bridge->funcs->detach(bridge);
err_reset_bridge:
bridge->dev = NULL;
bridge->encoder = NULL;
list_del(&bridge->chain_node);
#ifdef CONFIG_OF
DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
bridge->of_node, encoder->name, ret);
#else
DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
encoder->name, ret);
#endif
return ret;
}
三、connector数据结构
3.1 struct drm_connector
linux内核使用struct drm_connector来表示一个连接器，用于将encoder输出的信号传递给显示器，并与显示器建立连接；定义在include/drm/drm_connector.h:
点击查看代码
/**
* struct drm_connector - central DRM connector control structure
*
* Each connector may be connected to one or more CRTCs, or may be clonable by
* another connector if they can share a CRTC. Each connector also has a specific
* position in the broader display (referred to as a 'screen' though it could
* span multiple monitors).
*/
struct drm_connector {
/** @dev: parent DRM device */
struct drm_device *dev;
/** @kdev: kernel device for sysfs attributes */
struct device *kdev;
/** @attr: sysfs attributes */
struct device_attribute *attr;
/**
* @fwnode: associated fwnode supplied by platform firmware
*
* Drivers can set this to associate a fwnode with a connector, drivers
* are expected to get a reference on the fwnode when setting this.
* drm_connector_cleanup() will call fwnode_handle_put() on this.
*/
struct fwnode_handle *fwnode;
/**
* @head:
*
* List of all connectors on a @dev, linked from
* &drm_mode_config.connector_list. Protected by
* &drm_mode_config.connector_list_lock, but please only use
* &drm_connector_list_iter to walk this list.
*/
struct list_head head;
/**
* @global_connector_list_entry:
*
* Connector entry in the global connector-list, used by
* drm_connector_find_by_fwnode().
*/
struct list_head global_connector_list_entry;
/** @base: base KMS object */
struct drm_mode_object base;
/** @name: human readable name, can be overwritten by the driver */
char *name;
/**
* @mutex: Lock for general connector state, but currently only protects
* @registered. Most of the connector state is still protected by
* &drm_mode_config.mutex.
*/
struct mutex mutex;
/**
* @index: Compacted connector index, which matches the position inside
* the mode_config.list for drivers not supporting hot-add/removing. Can
* be used as an array index. It is invariant over the lifetime of the
* connector.
*/
unsigned index;
/**
* @connector_type:
* one of the DRM_MODE_CONNECTOR_<foo> types from drm_mode.h
*/
int connector_type;
/** @connector_type_id: index into connector type enum */
int connector_type_id;
/**
* @interlace_allowed:
* Can this connector handle interlaced modes? Only used by
* drm_helper_probe_single_connector_modes() for mode filtering.
*/
bool interlace_allowed;
/**
* @doublescan_allowed:
* Can this connector handle doublescan? Only used by
* drm_helper_probe_single_connector_modes() for mode filtering.
*/
bool doublescan_allowed;
/**
* @stereo_allowed:
* Can this connector handle stereo modes? Only used by
* drm_helper_probe_single_connector_modes() for mode filtering.
*/
bool stereo_allowed;
/**
* @ycbcr_420_allowed : This bool indicates if this connector is
* capable of handling YCBCR 420 output. While parsing the EDID
* blocks it's very helpful to know if the source is capable of
* handling YCBCR 420 outputs.
*/
bool ycbcr_420_allowed;
/**
* @registration_state: Is this connector initializing, exposed
* (registered) with userspace, or unregistered?
*
* Protected by @mutex.
*/
enum drm_connector_registration_state registration_state;
/**
* @modes:
* Modes available on this connector (from fill_modes() + user).
* Protected by &drm_mode_config.mutex.
*/
struct list_head modes;
/**
* @status:
* One of the drm_connector_status enums (connected, not, or unknown).
* Protected by &drm_mode_config.mutex.
*/
enum drm_connector_status status;
/**
* @probed_modes:
* These are modes added by probing with DDC or the BIOS, before
* filtering is applied. Used by the probe helpers. Protected by
* &drm_mode_config.mutex.
*/
struct list_head probed_modes;
/**
* @display_info: Display information is filled from EDID information
* when a display is detected. For non hot-pluggable displays such as
* flat panels in embedded systems, the driver should initialize the
* &drm_display_info.width_mm and &drm_display_info.height_mm fields
* with the physical size of the display.
*
* Protected by &drm_mode_config.mutex.
*/
struct drm_display_info display_info;
/** @funcs: connector control functions */
const struct drm_connector_funcs *funcs;
/**
* @edid_blob_ptr: DRM property containing EDID if present. Protected by
* &drm_mode_config.mutex. This should be updated only by calling
* drm_connector_update_edid_property().
*/
struct drm_property_blob *edid_blob_ptr;
/** @properties: property tracking for this connector */
struct drm_object_properties properties;
/**
* @scaling_mode_property: Optional atomic property to control the
* upscaling. See drm_connector_attach_content_protection_property().
*/
struct drm_property *scaling_mode_property;
/**
* @vrr_capable_property: Optional property to help userspace
* query hardware support for variable refresh rate on a connector.
* connector. Drivers can add the property to a connector by
* calling drm_connector_attach_vrr_capable_property().
*
* This should be updated only by calling
* drm_connector_set_vrr_capable_property().
*/
struct drm_property *vrr_capable_property;
/**
* @colorspace_property: Connector property to set the suitable
* colorspace supported by the sink.
*/
struct drm_property *colorspace_property;
/**
* @path_blob_ptr:
*
* DRM blob property data for the DP MST path property. This should only
* be updated by calling drm_connector_set_path_property().
*/
struct drm_property_blob *path_blob_ptr;
/**
* @max_bpc_property: Default connector property for the max bpc to be
* driven out of the connector.
*/
struct drm_property *max_bpc_property;
/** @privacy_screen: drm_privacy_screen for this connector, or NULL. */
struct drm_privacy_screen *privacy_screen;
/** @privacy_screen_notifier: privacy-screen notifier_block */
struct notifier_block privacy_screen_notifier;
/**
* @privacy_screen_sw_state_property: Optional atomic property for the
* connector to control the integrated privacy screen.
*/
struct drm_property *privacy_screen_sw_state_property;
/**
* @privacy_screen_hw_state_property: Optional atomic property for the
* connector to report the actual integrated privacy screen state.
*/
struct drm_property *privacy_screen_hw_state_property;
#define DRM_CONNECTOR_POLL_HPD (1 << 0)
#define DRM_CONNECTOR_POLL_CONNECT (1 << 1)
#define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2)
/**
* @polled:
*
* Connector polling mode, a combination of
*
* DRM_CONNECTOR_POLL_HPD
* The connector generates hotplug events and doesn't need to be
* periodically polled. The CONNECT and DISCONNECT flags must not
* be set together with the HPD flag.
*
* DRM_CONNECTOR_POLL_CONNECT
* Periodically poll the connector for connection.
*
* DRM_CONNECTOR_POLL_DISCONNECT
* Periodically poll the connector for disconnection, without
* causing flickering even when the connector is in use. DACs should
* rarely do this without a lot of testing.
*
* Set to 0 for connectors that don't support connection status
* discovery.
*/
uint8_t polled;
/**
* @dpms: Current dpms state. For legacy drivers the
* &drm_connector_funcs.dpms callback must update this. For atomic
* drivers, this is handled by the core atomic code, and drivers must
* only take &drm_crtc_state.active into account.
*/
int dpms;
/** @helper_private: mid-layer private data */
const struct drm_connector_helper_funcs *helper_private;
/** @cmdline_mode: mode line parsed from the kernel cmdline for this connector */
struct drm_cmdline_mode cmdline_mode;
/** @force: a DRM_FORCE_<foo> state for forced mode sets */
enum drm_connector_force force;
/**
* @edid_override: Override EDID set via debugfs.
*
* Do not modify or access outside of the drm_edid_override_* family of
* functions.
*/
const struct drm_edid *edid_override;
/**
* @edid_override_mutex: Protect access to edid_override.
*/
struct mutex edid_override_mutex;
/** @epoch_counter: used to detect any other changes in connector, besides status */
u64 epoch_counter;
/**
* @possible_encoders: Bit mask of encoders that can drive this
* connector, drm_encoder_index() determines the index into the bitfield
* and the bits are set with drm_connector_attach_encoder().
*/
u32 possible_encoders;
/**
* @encoder: Currently bound encoder driving this connector, if any.
* Only really meaningful for non-atomic drivers. Atomic drivers should
* instead look at &drm_connector_state.best_encoder, and in case they
* need the CRTC driving this output, &drm_connector_state.crtc.
*/
struct drm_encoder *encoder;
#define MAX_ELD_BYTES 128
/** @eld: EDID-like data, if present */
uint8_t eld[MAX_ELD_BYTES];
/** @latency_present: AV delay info from ELD, if found */
bool latency_present[2];
/**
* @video_latency: Video latency info from ELD, if found.
* [0]: progressive, [1]: interlaced
*/
int video_latency[2];
/**
* @audio_latency: audio latency info from ELD, if found
* [0]: progressive, [1]: interlaced
*/
int audio_latency[2];
/**
* @ddc: associated ddc adapter.
* A connector usually has its associated ddc adapter. If a driver uses
* this field, then an appropriate symbolic link is created in connector
* sysfs directory to make it easy for the user to tell which i2c
* adapter is for a particular display.
*
* The field should be set by calling drm_connector_init_with_ddc().
*/
struct i2c_adapter *ddc;
/**
* @null_edid_counter: track sinks that give us all zeros for the EDID.
* Needed to workaround some HW bugs where we get all 0s
*/
int null_edid_counter;
/** @bad_edid_counter: track sinks that give us an EDID with invalid checksum */
unsigned bad_edid_counter;
/**
* @edid_corrupt: Indicates whether the last read EDID was corrupt. Used
* in Displayport compliance testing - Displayport Link CTS Core 1.2
* rev1.1 4.2.2.6
*/
bool edid_corrupt;
/**
* @real_edid_checksum: real edid checksum for corrupted edid block.
* Required in Displayport 1.4 compliance testing
* rev1.1 4.2.2.6
*/
u8 real_edid_checksum;
/** @debugfs_entry: debugfs directory for this connector */
struct dentry *debugfs_entry;
/**
* @state:
*
* Current atomic state for this connector.
*
* This is protected by &drm_mode_config.connection_mutex. Note that
* nonblocking atomic commits access the current connector state without
* taking locks. Either by going through the &struct drm_atomic_state
* pointers, see for_each_oldnew_connector_in_state(),
* for_each_old_connector_in_state() and
* for_each_new_connector_in_state(). Or through careful ordering of
* atomic commit operations as implemented in the atomic helpers, see
* &struct drm_crtc_commit.
*/
struct drm_connector_state *state;
/* DisplayID bits. FIXME: Extract into a substruct? */
/**
* @tile_blob_ptr:
*
* DRM blob property data for the tile property (used mostly by DP MST).
* This is meant for screens which are driven through separate display
* pipelines represented by &drm_crtc, which might not be running with
* genlocked clocks. For tiled panels which are genlocked, like
* dual-link LVDS or dual-link DSI, the driver should try to not expose
* the tiling and virtualize both &drm_crtc and &drm_plane if needed.
*
* This should only be updated by calling
* drm_connector_set_tile_property().
*/
struct drm_property_blob *tile_blob_ptr;
/** @has_tile: is this connector connected to a tiled monitor */
bool has_tile;
/** @tile_group: tile group for the connected monitor */
struct drm_tile_group *tile_group;
/** @tile_is_single_monitor: whether the tile is one monitor housing */
bool tile_is_single_monitor;
/** @num_h_tile: number of horizontal tiles in the tile group */
/** @num_v_tile: number of vertical tiles in the tile group */
uint8_t num_h_tile, num_v_tile;
/** @tile_h_loc: horizontal location of this tile */
/** @tile_v_loc: vertical location of this tile */
uint8_t tile_h_loc, tile_v_loc;
/** @tile_h_size: horizontal size of this tile. */
/** @tile_v_size: vertical size of this tile. */
uint16_t tile_h_size, tile_v_size;
/**
* @free_node:
*
* List used only by &drm_connector_list_iter to be able to clean up a
* connector from any context, in conjunction with
* &drm_mode_config.connector_free_work.
*/
struct llist_node free_node;
/** @hdr_sink_metadata: HDR Metadata Information read from sink */
struct hdr_sink_metadata hdr_sink_metadata;
};
3.1.1 struct drm_display_info
linux内核使用struct drm_display_info来表示当前连接的显示设备的显示信息，它包含了一系列成员变量，用来描述显示设备的物理尺寸、颜色格式、总线格式等信息。定义在include/drm/drm_connector.h:
/**
* struct drm_display_info - runtime data about the connected sink
*
* Describes a given display (e.g. CRT or flat panel) and its limitations. For
* fixed display sinks like built-in panels there's not much difference between
* this and &struct drm_connector. But for sinks with a real cable this
* structure is meant to describe all the things at the other end of the cable.
*
* For sinks which provide an EDID this can be filled out by calling
* drm_add_edid_modes().
*/
struct drm_display_info {
/**
* @width_mm: Physical width in mm.
*/
unsigned int width_mm;
/**
* @height_mm: Physical height in mm.
*/
unsigned int height_mm;
/**
* @bpc: Maximum bits per color channel. Used by HDMI and DP outputs.
*/
unsigned int bpc;
/**
* @subpixel_order: Subpixel order of LCD panels.
*/
enum subpixel_order subpixel_order;
#define DRM_COLOR_FORMAT_RGB444 (1<<0)
#define DRM_COLOR_FORMAT_YCBCR444 (1<<1)
#define DRM_COLOR_FORMAT_YCBCR422 (1<<2)
#define DRM_COLOR_FORMAT_YCBCR420 (1<<3)
/**
* @panel_orientation: Read only connector property for built-in panels,
* indicating the orientation of the panel vs the device's casing.
* drm_connector_init() sets this to DRM_MODE_PANEL_ORIENTATION_UNKNOWN.
* When not UNKNOWN this gets used by the drm_fb_helpers to rotate the
* fb to compensate and gets exported as prop to userspace.
*/
int panel_orientation;
/**
* @color_formats: HDMI Color formats, selects between RGB and YCrCb
* modes. Used DRM_COLOR_FORMAT\_ defines, which are _not_ the same ones
* as used to describe the pixel format in framebuffers, and also don't
* match the formats in @bus_formats which are shared with v4l.
*/
u32 color_formats;
/**
* @bus_formats: Pixel data format on the wire, somewhat redundant with
* @color_formats. Array of size @num_bus_formats encoded using
* MEDIA_BUS_FMT\_ defines shared with v4l and media drivers.
*/
const u32 *bus_formats;
/**
* @bus_formats: Pixel data format on the wire, somewhat redundant with
* @color_formats. Array of size @num_bus_formats encoded using
* MEDIA_BUS_FMT\_ defines shared with v4l and media drivers.
*/
const u32 *bus_formats;
/**
* @num_bus_formats: Size of @bus_formats array.
*/
unsigned int num_bus_formats;
/**
* @bus_flags: Additional information (like pixel signal polarity) for
* the pixel data on the bus, using &enum drm_bus_flags values
* DRM_BUS_FLAGS\_.
*/
u32 bus_flags;
/**
* @max_tmds_clock: Maximum TMDS clock rate supported by the
* sink in kHz. 0 means undefined.
*/
int max_tmds_clock;
/**
* @dvi_dual: Dual-link DVI sink?
*/
bool dvi_dual;
/**
* @is_hdmi: True if the sink is an HDMI device.
*
* This field shall be used instead of calling
* drm_detect_hdmi_monitor() when possible.
*/
bool is_hdmi;
/**
* @has_hdmi_infoframe: Does the sink support the HDMI infoframe?
*/
bool has_hdmi_infoframe;
/**
* @rgb_quant_range_selectable: Does the sink support selecting
* the RGB quantization range?
*/
bool rgb_quant_range_selectable;
/**
* @edid_hdmi_rgb444_dc_modes: Mask of supported hdmi deep color modes
* in RGB 4:4:4. Even more stuff redundant with @bus_formats.
*/
u8 edid_hdmi_rgb444_dc_modes;
/**
* @edid_hdmi_ycbcr444_dc_modes: Mask of supported hdmi deep color
* modes in YCbCr 4:4:4. Even more stuff redundant with @bus_formats.
*/
u8 edid_hdmi_ycbcr444_dc_modes;
/**
* @cea_rev: CEA revision of the HDMI sink.
*/
u8 cea_rev;
/**
* @hdmi: advance features of a HDMI sink.
*/
struct drm_hdmi_info hdmi;
/**
* @non_desktop: Non desktop display (HMD).
*/
bool non_desktop;
/**
* @monitor_range: Frequency range supported by monitor range descriptor
*/
struct drm_monitor_range_info monitor_range;
/**
* @luminance_range: Luminance range supported by panel
*/
struct drm_luminance_range_info luminance_range;
/**
* @mso_stream_count: eDP Multi-SST Operation (MSO) stream count from
* the DisplayID VESA vendor block. 0 for conventional Single-Stream
* Transport (SST), or 2 or 4 MSO streams.
*/
u8 mso_stream_count;
/**
* @mso_pixel_overlap: eDP MSO segment pixel overlap, 0-8 pixels.
*/
u8 mso_pixel_overlap;
/**
* @max_dsc_bpp: Maximum DSC target bitrate, if it is set to 0 the
* monitor's default value is used instead.
*/
u32 max_dsc_bpp;
/**
* @vics: Array of vics_len VICs. Internal to EDID parsing.
*/
u8 *vics;
/**
* @vics_len: Number of elements in vics. Internal to EDID parsing.
*/
int vics_len;
/**
* @quirks: EDID based quirks. Internal to EDID parsing.
*/
u32 quirks;
};
其中：
width_mm：物理宽度，单位mm；height_mm：物理高度、单位mm；bpc: 每个颜色通道最大位数，适用于HDMI、DP输出；panel_orientation：一个只读属性，用于描述内置面板的方向与设备外壳的方向之间的关系。在调用drm_connector_init()函数时，这个属性会被设置为DRM_MODE_PANEL_ORIENTATION_UNKNOWN，表示方向未知。当方向不是未知时，图形驱动程序中的drm_fb_helpers会根据该属性来旋转帧缓冲以进行补偿，并将其作为属性导出给用户空间；color_formats：用于选择HDMI的颜色格式，支持RGB和YCrCb模式；这里使用了DRM_COLOR_FORMAT_定义的值来表示不同的颜色格式，这些值与用于描述framebuffer中像素格式的值是不同的。此外，它们也与与v4l共享的bus_formats中的格式不匹配；bus_formats：表示在传输介质上的像素数据格式，与color_formats相比有些冗余。bus_formats是一个数组，其大小由num_bus_formats确定，使用MEDIA_BUS_FMT_定义对其进行编码，这些定义是和v4l（以及媒体驱动程序共享的；num_bus_formats：bus_formats数组的长度；bus_flags：它包含了有关总线上像素数据的附加信息，比如像素信号的极性。这些信息使用enum drm_bus_flags中定义的数值，其中包括了DRM_BUS_FLAGS_前缀；max_tmds_clock：表示显示设备支持的TMDS时钟的最大速率，单位是千赫兹（kHz）。如果值为0，则表示未定义；dvi_dual：是否支持双链DVI；is_hdmi：用于指示显示设备是否为HDMI设备，通过设置该字段来避免不必要地调用drm_detect_hdmi_monitor函数；has_hdmi_infoframe：显示设备是否支持HDMI信息帧；rgb_quant_range_selectable：表示显示设备是否支持选择RGB量化范围；edid_hdmi_rgb444_dc_modes：用于表示支持的HDMI深色模式的位掩码，适用于RGB 4:4:4格式；edid_hdmi_ycbcr444_dc_modes：用于表示支持的HDMI深色模式的位掩码，适用于YCbCr 4:4:4格式；cea_rev：在HDMI接口中，CEA规范定义了一系列的视频和音频格式；该字段表示HDMI显示设备支持的CEA规范版本；hdmi：HDMI显示设备支持的高级功能；non_desktop：表示非桌面显示；monitor_range：存储从edid的``Detailed Monitor Descriptor`解析出的面板支持的频率范围；luminance_range：存储从edid的``static hdr metadata.`解析出的面板支持的亮度范围；mso_stream_count：eDP Multi-SST Operation（MSO）流计数是从DisplayID VESA供应商块中获取的信息。它用于指示eDP（Embedded DisplayPort）接口支持的传输模式；- 当
eDP接口使用传统的单流传输（SST）时，MSO流计数为0； - 当
eDP接口支持多流操作（MSO）时，MSO流计数可以是2或4；
- 当
mso_pixel_overlap：max_dsc_bpp：最大DSC目标比特率；vics：Array of vics_len VICs. Internal to EDID parsing；vics_len：Number of elements in vics. Internal to EDID parsing；quirks：EDID based quirks. Internal to EDID parsing.
3.1.2 struct drm_hdmi_info
linux内核使用struct drm_hdmi_info来表示当前连接的HDMI显示设备的信息，定义在include/drm/drm_connector.h:
/**
* struct drm_hdmi_info - runtime information about the connected HDMI sink
*
* Describes if a given display supports advanced HDMI 2.0 features.
* This information is available in CEA-861-F extension blocks (like HF-VSDB).
*/
struct drm_hdmi_info {
/** @scdc: sink's scdc support and capabilities */
struct drm_scdc scdc;
/**
* @y420_vdb_modes: bitmap of modes which can support ycbcr420
* output only (not normal RGB/YCBCR444/422 outputs). The max VIC
* defined by the CEA-861-G spec is 219, so the size is 256 bits to map
* up to 256 VICs.
*/
unsigned long y420_vdb_modes[BITS_TO_LONGS(256)];
/**
* @y420_cmdb_modes: bitmap of modes which can support ycbcr420
* output also, along with normal HDMI outputs. The max VIC defined by
* the CEA-861-G spec is 219, so the size is 256 bits to map up to 256
* VICs.
*/
unsigned long y420_cmdb_modes[BITS_TO_LONGS(256)];
/** @y420_dc_modes: bitmap of deep color support index */
u8 y420_dc_modes;
/** @max_frl_rate_per_lane: support fixed rate link */
u8 max_frl_rate_per_lane;
/** @max_lanes: supported by sink */
u8 max_lanes;
/** @dsc_cap: DSC capabilities of the sink */
struct drm_hdmi_dsc_cap dsc_cap;
};
3.2 操作函数
3.2.1 struct drm_connector_funcs
struct drm_connector_funcs用于描述connector的控制函数，定义在include/drm/drm_connector.h；
点击查看代码
/**
* struct drm_connector_funcs - control connectors on a given device
*
* Each CRTC may have one or more connectors attached to it. The functions
* below allow the core DRM code to control connectors, enumerate available modes,
* etc.
*/
struct drm_connector_funcs {
/**
* @dpms:
*
* Legacy entry point to set the per-connector DPMS state. Legacy DPMS
* is exposed as a standard property on the connector, but diverted to
* this callback in the drm core. Note that atomic drivers don't
* implement the 4 level DPMS support on the connector any more, but
* instead only have an on/off "ACTIVE" property on the CRTC object.
*
* This hook is not used by atomic drivers, remapping of the legacy DPMS
* property is entirely handled in the DRM core.
*
* RETURNS:
*
* 0 on success or a negative error code on failure.
*/
int (*dpms)(struct drm_connector *connector, int mode);
/**
* @reset:
*
* Reset connector hardware and software state to off. This function isn't
* called by the core directly, only through drm_mode_config_reset().
* It's not a helper hook only for historical reasons.
*
* Atomic drivers can use drm_atomic_helper_connector_reset() to reset
* atomic state using this hook.
*/
void (*reset)(struct drm_connector *connector);
/**
* @detect:
*
* Check to see if anything is attached to the connector. The parameter
* force is set to false whilst polling, true when checking the
* connector due to a user request. force can be used by the driver to
* avoid expensive, destructive operations during automated probing.
*
* This callback is optional, if not implemented the connector will be
* considered as always being attached.
*
* FIXME:
*
* Note that this hook is only called by the probe helper. It's not in
* the helper library vtable purely for historical reasons. The only DRM
* core entry point to probe connector state is @fill_modes.
*
* Note that the helper library will already hold
* &drm_mode_config.connection_mutex. Drivers which need to grab additional
* locks to avoid races with concurrent modeset changes need to use
* &drm_connector_helper_funcs.detect_ctx instead.
*
* Also note that this callback can be called no matter the
* state the connector is in. Drivers that need the underlying
* device to be powered to perform the detection will first need
* to make sure it's been properly enabled.
*
* RETURNS:
*
* drm_connector_status indicating the connector's status.
*/
enum drm_connector_status (*detect)(struct drm_connector *connector,
bool force);
/**
* @force:
*
* This function is called to update internal encoder state when the
* connector is forced to a certain state by userspace, either through
* the sysfs interfaces or on the kernel cmdline. In that case the
* @detect callback isn't called.
*
* FIXME:
*
* Note that this hook is only called by the probe helper. It's not in
* the helper library vtable purely for historical reasons. The only DRM
* core entry point to probe connector state is @fill_modes.
*/
void (*force)(struct drm_connector *connector);
/**
* @fill_modes:
*
* Entry point for output detection and basic mode validation. The
* driver should reprobe the output if needed (e.g. when hotplug
* handling is unreliable), add all detected modes to &drm_connector.modes
* and filter out any the device can't support in any configuration. It
* also needs to filter out any modes wider or higher than the
* parameters max_width and max_height indicate.
*
* The drivers must also prune any modes no longer valid from
* &drm_connector.modes. Furthermore it must update
* &drm_connector.status and &drm_connector.edid. If no EDID has been
* received for this output connector->edid must be NULL.
*
* Drivers using the probe helpers should use
* drm_helper_probe_single_connector_modes() to implement this
* function.
*
* RETURNS:
*
* The number of modes detected and filled into &drm_connector.modes.
*/
int (*fill_modes)(struct drm_connector *connector, uint32_t max_width, uint32_t max_height);
/**
* @set_property:
*
* This is the legacy entry point to update a property attached to the
* connector.
*
* This callback is optional if the driver does not support any legacy
* driver-private properties. For atomic drivers it is not used because
* property handling is done entirely in the DRM core.
*
* RETURNS:
*
* 0 on success or a negative error code on failure.
*/
int (*set_property)(struct drm_connector *connector, struct drm_property *property,
uint64_t val);
/**
* @late_register:
*
* This optional hook can be used to register additional userspace
* interfaces attached to the connector, light backlight control, i2c,
* DP aux or similar interfaces. It is called late in the driver load
* sequence from drm_connector_register() when registering all the
* core drm connector interfaces. Everything added from this callback
* should be unregistered in the early_unregister callback.
* should be unregistered in the early_unregister callback.
*
* This is called while holding &drm_connector.mutex.
*
* Returns:
*
* 0 on success, or a negative error code on failure.
*/
int (*late_register)(struct drm_connector *connector);
/**
* @early_unregister:
*
* This optional hook should be used to unregister the additional
* userspace interfaces attached to the connector from
* late_register(). It is called from drm_connector_unregister(),
* early in the driver unload sequence to disable userspace access
* before data structures are torndown.
*
* This is called while holding &drm_connector.mutex.
*/
void (*early_unregister)(struct drm_connector *connector);
/**
* @destroy:
*
* Clean up connector resources. This is called at driver unload time
* through drm_mode_config_cleanup(). It can also be called at runtime
* when a connector is being hot-unplugged for drivers that support
* connector hotplugging (e.g. DisplayPort MST).
*/
void (*destroy)(struct drm_connector *connector);
/**
* @atomic_duplicate_state:
*
* Duplicate the current atomic state for this connector and return it.
* The core and helpers guarantee that any atomic state duplicated with
* this hook and still owned by the caller (i.e. not transferred to the
* driver by calling &drm_mode_config_funcs.atomic_commit) will be
* cleaned up by calling the @atomic_destroy_state hook in this
* structure.
*
* This callback is mandatory for atomic drivers.
*
* Atomic drivers which don't subclass &struct drm_connector_state should use
* drm_atomic_helper_connector_duplicate_state(). Drivers that subclass the
* state structure to extend it with driver-private state should use
* __drm_atomic_helper_connector_duplicate_state() to make sure shared state is
* duplicated in a consistent fashion across drivers.
*
* It is an error to call this hook before &drm_connector.state has been
* initialized correctly.
*
* NOTE:
*
* If the duplicate state references refcounted resources this hook must
* acquire a reference for each of them. The driver must release these
* references again in @atomic_destroy_state.
*
* RETURNS:
*
* Duplicated atomic state or NULL when the allocation failed.
*/
struct drm_connector_state *(*atomic_duplicate_state)(struct drm_connector *connector);
/**
* @atomic_destroy_state:
*
* Destroy a state duplicated with @atomic_duplicate_state and release
* or unreference all resources it references
*
* This callback is mandatory for atomic drivers.
*/
void (*atomic_destroy_state)(struct drm_connector *connector,
struct drm_connector_state *state);
/**
* @atomic_set_property:
*
* Decode a driver-private property value and store the decoded value
* into the passed-in state structure. Since the atomic core decodes all
* standardized properties (even for extensions beyond the core set of
* properties which might not be implemented by all drivers) this
* requires drivers to subclass the state structure.
*
* Such driver-private properties should really only be implemented for
* truly hardware/vendor specific state. Instead it is preferred to
* standardize atomic extension and decode the properties used to expose
* such an extension in the core.
*
* Do not call this function directly, use
* drm_atomic_connector_set_property() instead.
*
* This callback is optional if the driver does not support any
* driver-private atomic properties.
*
* NOTE:
*
* This function is called in the state assembly phase of atomic
* modesets, which can be aborted for any reason (including on
* userspace's request to just check whether a configuration would be
* possible). Drivers MUST NOT touch any persistent state (hardware or
* software) or data structures except the passed in @state parameter.
*
* Also since userspace controls in which order properties are set this
* function must not do any input validation (since the state update is
* incomplete and hence likely inconsistent). Instead any such input
* validation must be done in the various atomic_check callbacks.
*
* RETURNS:
*
* 0 if the property has been found, -EINVAL if the property isn't
* implemented by the driver (which shouldn't ever happen, the core only
* asks for properties attached to this connector). No other validation
* is allowed by the driver. The core already checks that the property
* value is within the range (integer, valid enum value, ...) the driver
* set when registering the property.
*/
int (*atomic_set_property)(struct drm_connector *connector,
struct drm_connector_state *state,
struct drm_property *property,
uint64_t val);
/**
* @atomic_get_property:
*
* Reads out the decoded driver-private property. This is used to
* implement the GETCONNECTOR IOCTL.
*
* Do not call this function directly, use
* drm_atomic_connector_get_property() instead.
*
* This callback is optional if the driver does not support any
* driver-private atomic properties.
*
* RETURNS:
*
* 0 on success, -EINVAL if the property isn't implemented by the
* driver (which shouldn't ever happen, the core only asks for
* properties attached to this connector).
*/
int (*atomic_get_property)(struct drm_connector *connector,
const struct drm_connector_state *state,
struct drm_property *property,
uint64_t *val);
/**
* @atomic_print_state:
*
* If driver subclasses &struct drm_connector_state, it should implement
* this optional hook for printing additional driver specific state.
*
* Do not call this directly, use drm_atomic_connector_print_state()
* instead.
*/
void (*atomic_print_state)(struct drm_printer *p,
const struct drm_connector_state *state);
/**
* @oob_hotplug_event:
*
* This will get called when a hotplug-event for a drm-connector
* has been received from a source outside the display driver / device.
*/
void (*oob_hotplug_event)(struct drm_connector *connector);
/**
* @debugfs_init:
*
* Allows connectors to create connector-specific debugfs files.
*/
void (*debugfs_init)(struct drm_connector *connector, struct dentry *root);
};
3.2.2 struct drm_connector_helper_funcs
struct drm_connector_helper_funcs定义了一些常用的connector辅助操作函数，定义在include/drm/drm_modeset_helper_vtables.h；
点击查看代码
/**
* struct drm_connector_helper_funcs - helper operations for connectors
*
* These functions are used by the atomic and legacy modeset helpers and by the
* probe helpers.
*/
struct drm_connector_helper_funcs {
/**
* @get_modes:
*
* This function should fill in all modes currently valid for the sink
* into the &drm_connector.probed_modes list. It should also update the
* EDID property by calling drm_connector_update_edid_property().
*
* The usual way to implement this is to cache the EDID retrieved in the
* probe callback somewhere in the driver-private connector structure.
* In this function drivers then parse the modes in the EDID and add
* them by calling drm_add_edid_modes(). But connectors that drive a
* fixed panel can also manually add specific modes using
* drm_mode_probed_add(). Drivers which manually add modes should also
* make sure that the &drm_connector.display_info,
* &drm_connector.width_mm and &drm_connector.height_mm fields are
* filled in.
*
* Note that the caller function will automatically add standard VESA
* DMT modes up to 1024x768 if the .get_modes() helper operation returns
* no mode and if the connector status is connector_status_connected or
* connector_status_unknown. There is no need to call
* drm_add_modes_noedid() manually in that case.
*
* Virtual drivers that just want some standard VESA mode with a given
* resolution can call drm_add_modes_noedid(), and mark the preferred
* one using drm_set_preferred_mode().
*
* This function is only called after the @detect hook has indicated
* that a sink is connected and when the EDID isn't overridden through
* sysfs or the kernel commandline.
*
* This callback is used by the probe helpers in e.g.
* drm_helper_probe_single_connector_modes().
*
* To avoid races with concurrent connector state updates, the helper
* libraries always call this with the &drm_mode_config.connection_mutex
* held. Because of this it's safe to inspect &drm_connector->state.
*
* RETURNS:
*
* The number of modes added by calling drm_mode_probed_add().
*/
int (*get_modes)(struct drm_connector *connector);
/**
* @detect_ctx:
*
* Check to see if anything is attached to the connector. The parameter
* force is set to false whilst polling, true when checking the
* connector due to a user request. force can be used by the driver to
* avoid expensive, destructive operations during automated probing.
*
* This callback is optional, if not implemented the connector will be
* considered as always being attached.
*
* This is the atomic version of &drm_connector_funcs.detect.
*
* To avoid races against concurrent connector state updates, the
* helper libraries always call this with ctx set to a valid context,
* and &drm_mode_config.connection_mutex will always be locked with
* the ctx parameter set to this ctx. This allows taking additional
* locks as required.
*
*
* RETURNS:
*
* &drm_connector_status indicating the connector's status,
* or the error code returned by drm_modeset_lock(), -EDEADLK.
*/
int (*detect_ctx)(struct drm_connector *connector,
struct drm_modeset_acquire_ctx *ctx,
bool force);
/**
* @mode_valid:
*
* Callback to validate a mode for a connector, irrespective of the
* specific display configuration.
*
* This callback is used by the probe helpers to filter the mode list
* (which is usually derived from the EDID data block from the sink).
* See e.g. drm_helper_probe_single_connector_modes().
*
* This function is optional.
*
* NOTE:
*
* This only filters the mode list supplied to userspace in the
* GETCONNECTOR IOCTL. Compared to &drm_encoder_helper_funcs.mode_valid,
* &drm_crtc_helper_funcs.mode_valid and &drm_bridge_funcs.mode_valid,
* which are also called by the atomic helpers from
* drm_atomic_helper_check_modeset(). This allows userspace to force and
* ignore sink constraint (like the pixel clock limits in the screen's
* EDID), which is useful for e.g. testing, or working around a broken
* EDID. Any source hardware constraint (which always need to be
* enforced) therefore should be checked in one of the above callbacks,
* and not this one here.
*
* To avoid races with concurrent connector state updates, the helper
* libraries always call this with the &drm_mode_config.connection_mutex
* held. Because of this it's safe to inspect &drm_connector->state.
*
* RETURNS:
*
* Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum
* drm_mode_status.
*/
enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
struct drm_display_mode *mode);
/**
* @mode_valid_ctx:
*
* Callback to validate a mode for a connector, irrespective of the
* specific display configuration.
*
* This callback is used by the probe helpers to filter the mode list
* (which is usually derived from the EDID data block from the sink).
* See e.g. drm_helper_probe_single_connector_modes().
*
* This function is optional, and is the atomic version of
* &drm_connector_helper_funcs.mode_valid.
*
* To allow for accessing the atomic state of modesetting objects, the
* helper libraries always call this with ctx set to a valid context,
* and &drm_mode_config.connection_mutex will always be locked with
* the ctx parameter set to @ctx. This allows for taking additional
* locks as required.
*
* Even though additional locks may be acquired, this callback is
* still expected not to take any constraints into account which would
* be influenced by the currently set display state - such constraints
* should be handled in the driver's atomic check. For example, if a
* connector shares display bandwidth with other connectors then it
* would be ok to validate the minimum bandwidth requirement of a mode
* against the maximum possible bandwidth of the connector. But it
* wouldn't be ok to take the current bandwidth usage of other
* connectors into account, as this would change depending on the
* display state.
*
* Returns:
* 0 if &drm_connector_helper_funcs.mode_valid_ctx succeeded and wrote
* the &enum drm_mode_status value to @status, or a negative error
* code otherwise.
*
*/
int (*mode_valid_ctx)(struct drm_connector *connector,
struct drm_display_mode *mode,
struct drm_modeset_acquire_ctx *ctx,
enum drm_mode_status *status);
/**
* @best_encoder:
*
* This function should select the best encoder for the given connector.
*
* This function is used by both the atomic helpers (in the
* drm_atomic_helper_check_modeset() function) and in the legacy CRTC
* helpers.
*
* NOTE:
*
* In atomic drivers this function is called in the check phase of an
* atomic update. The driver is not allowed to change or inspect
* anything outside of arguments passed-in. Atomic drivers which need to
* inspect dynamic configuration state should instead use
* @atomic_best_encoder.
*
* You can leave this function to NULL if the connector is only
* attached to a single encoder. In this case, the core will call
* drm_connector_get_single_encoder() for you.
*
* RETURNS:
*
* Encoder that should be used for the given connector and connector
* state, or NULL if no suitable encoder exists. Note that the helpers
* will ensure that encoders aren't used twice, drivers should not check
* for this.
*/
struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
/**
* @atomic_best_encoder:
*
* This is the atomic version of @best_encoder for atomic drivers which
* need to select the best encoder depending upon the desired
* configuration and can't select it statically.
*
* This function is used by drm_atomic_helper_check_modeset().
* If it is not implemented, the core will fallback to @best_encoder
* (or drm_connector_get_single_encoder() if @best_encoder is NULL).
*
* NOTE:
*
* This function is called in the check phase of an atomic update. The
* driver is not allowed to change anything outside of the
* &drm_atomic_state update tracking structure passed in.
*
* RETURNS:
*
* Encoder that should be used for the given connector and connector
* state, or NULL if no suitable encoder exists. Note that the helpers
* will ensure that encoders aren't used twice, drivers should not check
* for this.
*/
struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
struct drm_atomic_state *state);
/**
* @atomic_check:
*
* This hook is used to validate connector state. This function is
* called from &drm_atomic_helper_check_modeset, and is called when
* a connector property is set, or a modeset on the crtc is forced.
*
* Because &drm_atomic_helper_check_modeset may be called multiple times,
* this function should handle being called multiple times as well.
*
* This function is also allowed to inspect any other object's state and
* can add more state objects to the atomic commit if needed. Care must
* be taken though to ensure that state check and compute functions for
* these added states are all called, and derived state in other objects
* all updated. Again the recommendation is to just call check helpers
* until a maximal configuration is reached.
*
* NOTE:
*
* This function is called in the check phase of an atomic update. The
* driver is not allowed to change anything outside of the free-standing
* state objects passed-in or assembled in the overall &drm_atomic_state
* update tracking structure.
*
* RETURNS:
*
* 0 on success, -EINVAL if the state or the transition can't be
* supported, -ENOMEM on memory allocation failure and -EDEADLK if an
* attempt to obtain another state object ran into a &drm_modeset_lock
* deadlock.
*/
int (*atomic_check)(struct drm_connector *connector,
struct drm_atomic_state *state);
/**
* @atomic_commit:
*
* This hook is to be used by drivers implementing writeback connectors
* that need a point when to commit the writeback job to the hardware.
* The writeback_job to commit is available in the new connector state,
* in &drm_connector_state.writeback_job.
*
* This hook is optional.
*
* This callback is used by the atomic modeset helpers.
*/
void (*atomic_commit)(struct drm_connector *connector,
struct drm_atomic_state *state);
/**
* @prepare_writeback_job:
*
* As writeback jobs contain a framebuffer, drivers may need to
* prepare and clean them up the same way they can prepare and
* clean up framebuffers for planes. This optional connector operation
* is used to support the preparation of writeback jobs. The job
* prepare operation is called from drm_atomic_helper_prepare_planes()
* for struct &drm_writeback_connector connectors only.
*
* This operation is optional.
*
* This callback is used by the atomic modeset helpers.
*/
int (*prepare_writeback_job)(struct drm_writeback_connector *connector,
struct drm_writeback_job *job);
/**
* @cleanup_writeback_job:
*
* This optional connector operation is used to support the
* cleanup of writeback jobs. The job cleanup operation is called
* from the existing drm_writeback_cleanup_job() function, invoked
* both when destroying the job as part of an aborted commit, or when
* the job completes.
*
* This operation is optional.
*
* This callback is used by the atomic modeset helpers.
*/
void (*cleanup_writeback_job)(struct drm_writeback_connector *connector,
struct drm_writeback_job *job);
/**
* @enable_hpd:
*
* Enable hot-plug detection for the connector.
*
* This operation is optional.
*
* This callback is used by the drm_kms_helper_poll_enable() helpers.
*/
void (*enable_hpd)(struct drm_connector *connector);
/**
* @disable_hpd:
*
* Disable hot-plug detection for the connector.
*
* This operation is optional.
*
* This callback is used by the drm_kms_helper_poll_disable() helpers.
*/
void (*disable_hpd)(struct drm_connector *connector);
};
四、encoder 核心API
4.1 encoder初始化
drm_encoder_init函数用于初始化encoder对象，定义在drivers/gpu/drm/drm_encoder.c；
/**
* drm_encoder_init - Init a preallocated encoder
* @dev: drm device
* @encoder: the encoder to init
* @funcs: callbacks for this encoder
* @encoder_type: user visible type of the encoder
* @name: printf style format string for the encoder name, or NULL for default name
*
* Initializes a preallocated encoder. Encoder should be subclassed as part of
* driver encoder objects. At driver unload time the driver's
* &drm_encoder_funcs.destroy hook should call drm_encoder_cleanup() and kfree()
* the encoder structure. The encoder structure should not be allocated with
* devm_kzalloc().
*
* Note: consider using drmm_encoder_alloc() or drmm_encoder_init()
* instead of drm_encoder_init() to let the DRM managed resource
* infrastructure take care of cleanup and deallocation.
*
* Returns:
* Zero on success, error code on failure.
*/
int drm_encoder_init(struct drm_device *dev,
struct drm_encoder *encoder,
const struct drm_encoder_funcs *funcs,
int encoder_type, const char *name, ...)
{
va_list ap;
int ret;
WARN_ON(!funcs->destroy);
va_start(ap, name);
ret = __drm_encoder_init(dev, encoder, funcs, encoder_type, name, ap);
va_end(ap);
return ret;
}
具体实现位于函数__drm_encoder_init：
__printf(5, 0)
static int __drm_encoder_init(struct drm_device *dev,
struct drm_encoder *encoder,
const struct drm_encoder_funcs *funcs,
int encoder_type, const char *name, va_list ap)
{
int ret;
/* encoder index is used with 32bit bitmasks */
if (WARN_ON(dev->mode_config.num_encoder >= 32))
return -EINVAL;
ret = drm_mode_object_add(dev, &encoder->base, DRM_MODE_OBJECT_ENCODER);
if (ret)
return ret;
encoder->dev = dev;
encoder->encoder_type = encoder_type;
encoder->funcs = funcs;
if (name) {
encoder->name = kvasprintf(GFP_KERNEL, name, ap);
} else {
encoder->name = kasprintf(GFP_KERNEL, "%s-%d",
drm_encoder_enum_list[encoder_type].name,
encoder->base.id);
}
if (!encoder->name) {
ret = -ENOMEM;
goto out_put;
}
INIT_LIST_HEAD(&encoder->bridge_chain);
list_add_tail(&encoder->head, &dev->mode_config.encoder_list);
encoder->index = dev->mode_config.num_encoder++;
out_put:
if (ret)
drm_mode_object_unregister(dev, &encoder->base);
return ret;
}
4.2 encoder注册
drm_encoder_register_all函数用于初始化encoder对象，定义在drivers/gpu/drm/drm_encoder.c；
int drm_encoder_register_all(struct drm_device *dev)
{
struct drm_encoder *encoder;
int ret = 0;
drm_for_each_encoder(encoder, dev) {
if (encoder->funcs && encoder->funcs->late_register)
ret = encoder->funcs->late_register(encoder);
if (ret)
return ret;
}
return 0;
}
这里直接遍历drm_device->mode_config的encoder_list链表，依次调用encoder->funcs->late_register。
五、encoder 核心API
5.1 connector初始化
drm_connector_init函数用于初始化connector对象，定义在drivers/gpu/drm/drm_connector.c；
/**
* drm_connector_init - Init a preallocated connector
* @dev: DRM device
* @connector: the connector to init
* @funcs: callbacks for this connector
* @connector_type: user visible type of the connector
*
* Initialises a preallocated connector. Connectors should be
* subclassed as part of driver connector objects.
*
* At driver unload time the driver's &drm_connector_funcs.destroy hook
* should call drm_connector_cleanup() and free the connector structure.
* The connector structure should not be allocated with devm_kzalloc().
*
* Note: consider using drmm_connector_init() instead of
* drm_connector_init() to let the DRM managed resource infrastructure
* take care of cleanup and deallocation.
*
* Returns:
* Zero on success, error code on failure.
*/
int drm_connector_init(struct drm_device *dev,
struct drm_connector *connector,
const struct drm_connector_funcs *funcs,
int connector_type)
{
if (drm_WARN_ON(dev, !(funcs && funcs->destroy)))
return -EINVAL;
return __drm_connector_init(dev, connector, funcs, connector_type, NULL);
}
具体实现位于函数__drm_connector_init：
static int __drm_connector_init(struct drm_device *dev,
struct drm_connector *connector,
const struct drm_connector_funcs *funcs,
int connector_type,
struct i2c_adapter *ddc)
{
struct drm_mode_config *config = &dev->mode_config;
int ret;
struct ida *connector_ida =
&drm_connector_enum_list[connector_type].ida;
WARN_ON(drm_drv_uses_atomic_modeset(dev) &&
(!funcs->atomic_destroy_state ||
!funcs->atomic_duplicate_state));
ret = __drm_mode_object_add(dev, &connector->base,
DRM_MODE_OBJECT_CONNECTOR,
false, drm_connector_free);
if (ret)
return ret;
connector->base.properties = &connector->properties;
connector->dev = dev;
connector->funcs = funcs;
/* connector index is used with 32bit bitmasks */
ret = ida_alloc_max(&config->connector_ida, 31, GFP_KERNEL);
if (ret < 0) {
DRM_DEBUG_KMS("Failed to allocate %s connector index: %d\n",
drm_connector_enum_list[connector_type].name,
ret);
goto out_put;
}
connector->index = ret;
ret = 0;
connector->connector_type = connector_type;
connector->connector_type_id =
ida_alloc_min(connector_ida, 1, GFP_KERNEL);
if (connector->connector_type_id < 0) {
ret = connector->connector_type_id;
goto out_put_id;
}
connector->name =
kasprintf(GFP_KERNEL, "%s-%d",
drm_connector_enum_list[connector_type].name,
connector->connector_type_id);
if (!connector->name) {
ret = -ENOMEM;
goto out_put_type_id;
}
/* provide ddc symlink in sysfs */
connector->ddc = ddc;
INIT_LIST_HEAD(&connector->global_connector_list_entry);
INIT_LIST_HEAD(&connector->probed_modes);
INIT_LIST_HEAD(&connector->modes);
mutex_init(&connector->mutex);
mutex_init(&connector->edid_override_mutex);
connector->edid_blob_ptr = NULL;
connector->epoch_counter = 0;
connector->tile_blob_ptr = NULL;
connector->status = connector_status_unknown;
connector->display_info.panel_orientation =
DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
drm_connector_get_cmdline_mode(connector);
/* We should add connectors at the end to avoid upsetting the connector
* index too much.
*/
spin_lock_irq(&config->connector_list_lock);
list_add_tail(&connector->head, &config->connector_list);
config->num_connector++;
spin_unlock_irq(&config->connector_list_lock);
if (connector_type != DRM_MODE_CONNECTOR_VIRTUAL &&
connector_type != DRM_MODE_CONNECTOR_WRITEBACK)
drm_connector_attach_edid_property(connector);
drm_object_attach_property(&connector->base,
config->dpms_property, 0);
drm_object_attach_property(&connector->base,
config->link_status_property,
0);
drm_object_attach_property(&connector->base,
config->non_desktop_property,
0);
drm_object_attach_property(&connector->base,
config->tile_property,
0);
if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
}
connector->debugfs_entry = NULL;
out_put_type_id:
if (ret)
ida_free(connector_ida, connector->connector_type_id);
out_put_id:
if (ret)
ida_free(&config->connector_ida, connector->index);
out_put:
if (ret)
drm_mode_object_unregister(dev, &connector->base);
return ret;
}
5.2 connector注册
drm_connector_register_all函数用于初始化connector对象，定义在drivers/gpu/drm/drm_connector.c；
int drm_connector_register_all(struct drm_device *dev)
{
struct drm_connector *connector;
struct drm_connector_list_iter conn_iter;
int ret = 0;
drm_connector_list_iter_begin(dev, &conn_iter);
drm_for_each_connector_iter(connector, &conn_iter) {
ret = drm_connector_register(connector);
if (ret)
break;
}
drm_connector_list_iter_end(&conn_iter);
if (ret)
drm_connector_unregister_all(dev);
return ret;
}
这里直接遍历drm_device->mode_config的connector_list链表，依次调用drm_connector_register注册每一个connector；
/**
* drm_connector_register - register a connector
* @connector: the connector to register
*
* Register userspace interfaces for a connector. Only call this for connectors
* which can be hotplugged after drm_dev_register() has been called already,
* e.g. DP MST connectors. All other connectors will be registered automatically
* when calling drm_dev_register().
*
* When the connector is no longer available, callers must call
* drm_connector_unregister().
*
* Returns:
* Zero on success, error code on failure.
*/
int drm_connector_register(struct drm_connector *connector)
{
int ret = 0;
// 检查设备是否已经注册，如果没有注册则直接返回成功
if (!connector->dev->registered)
return 0;
// 互斥锁
mutex_lock(&connector->mutex);
// 检查connector的注册状态，如果不是正在初始化状态则解锁并返回
if (connector->registration_state != DRM_CONNECTOR_INITIALIZING)
goto unlock;
// 1. 关于DRM子系统中的sysfs接口，比如在sysfs创建/sys/class/drm/card0-HDMI-A-1
ret = drm_sysfs_connector_add(connector);
if (ret)
goto unlock;
// 2. 关于DRM子系统中的sysfs接口，比如在debugfs创建/sys/kernel/debug/dri/0/HDMI-A-1
drm_debugfs_connector_add(connector);
// 3. 如果定义了late_register函数，回调该函数
if (connector->funcs->late_register) {
ret = connector->funcs->late_register(connector);
if (ret)
goto err_debugfs;
}
// 通过connector->dev获取到对应的drm_device，然后注册connector这个modeset object
drm_mode_object_register(connector->dev, &connector->base);
// 更新注册状态
connector->registration_state = DRM_CONNECTOR_REGISTERED;
/* Let userspace know we have a new connector */
drm_sysfs_connector_hotplug_event(connector);
if (connector->privacy_screen)
drm_privacy_screen_register_notifier(connector->privacy_screen,
&connector->privacy_screen_notifier);
mutex_lock(&connector_list_lock);
// 将当前connector添加到connector_list链表
list_add_tail(&connector->global_connector_list_entry, &connector_list);
mutex_unlock(&connector_list_lock);
goto unlock;
err_debugfs:
drm_debugfs_connector_remove(connector);
drm_sysfs_connector_remove(connector);
unlock:
mutex_unlock(&connector->mutex);
return ret;
}
5.2.1 drm_sysfs_connector_add
drm_sysfs_connector_add函数位于drivers/gpu/drm/drm_sysfs.c，这段代码是关于DRM子系统中的sysfs接口的实现。主要作用是在sysfs中添加connector的相关信息。
static DEVICE_ATTR_RW(status);
static DEVICE_ATTR_RO(enabled);
static DEVICE_ATTR_RO(dpms);
static DEVICE_ATTR_RO(modes);
static struct attribute *connector_dev_attrs[] = {
&dev_attr_status.attr,
&dev_attr_enabled.attr,
&dev_attr_dpms.attr,
&dev_attr_modes.attr,
NULL
};
// edid文件属性
static struct bin_attribute edid_attr = {
.attr.name = "edid",
.attr.mode = 0444,
.size = 0,
.read = edid_show,
};
static struct bin_attribute *connector_bin_attrs[] = {
&edid_attr,
NULL
};
static const struct attribute_group connector_dev_group = {
.attrs = connector_dev_attrs,
.bin_attrs = connector_bin_attrs,
};
static const struct attribute_group *connector_dev_groups[] = {
&connector_dev_group,
NULL
};
int drm_sysfs_connector_add(struct drm_connector *connector)
{
struct drm_device *dev = connector->dev;
struct device *kdev;
int r;
if (connector->kdev)
return 0;
// 动态分配内存，指向struct device
kdev = kzalloc(sizeof(*kdev), GFP_KERNEL);
if (!kdev)
return -ENOMEM;
// 初始化设备，这个函数是device_register函数的前半部分的实现，主要用于设备的初始化
device_initialize(kdev);
// 设置设备class
kdev->class = drm_class;
kdev->type = &drm_sysfs_device_connector;
// 设置父设备，一般为显卡设备card0，位于/sys/devices/platform/display-subsystem/drm/card0/
kdev->parent = dev->primary->kdev;
kdev->groups = connector_dev_groups;
kdev->release = drm_sysfs_release;
// 设置驱动私有数据
dev_set_drvdata(kdev, connector);
// 设置设备名称 比如：card0-HDMI-A-1
r = dev_set_name(kdev, "card%d-%s", dev->primary->index, connector->name);
if (r)
goto err_free;
DRM_DEBUG("adding \"%s\" to sysfs\n",
connector->name);
// 在/sys/class/drm/创建card%d-%s文件，由于没有设置主设备号，并不会创建设备节点/dev/drm/card%d-%s
r = device_add(kdev);
if (r) {
drm_err(dev, "failed to register connector device: %d\n", r);
goto err_free;
}
connector->kdev = kdev;
// 连接器如果指定了ddc通道
if (connector->ddc)
// 创建ddc链接文件
return sysfs_create_link(&connector->kdev->kobj,
&connector->ddc->dev.kobj, "ddc");
return 0;
err_free:
put_device(kdev);
return r;
}
该函数：
- 首先调用
device_initialize函数对kdev进行初始化设置，包括设置设备的类别、类型、父设备等信息，以及设置驱动私有数据； - 然后会调用
dev_set_name函数为kdev设置设备名称； - 之后会调用
device_add函数将kdev添加到sysfs中，并在/sys/class/drm/创建card%d-%s文件； - 如果添加成功，则将
kdev对象赋值给连接器的kdev成员变量。
整个过程的作用是将connector的属性添加到sysfs中，使用户空间能够访问和控制connector。
以HDMI驱动为例，其会完成connector以及encoder的初始化和注册，因此我们可以在sysfs文件系统看到：
root@rk3399:~# ll /sys/class/drm
lrwxrwxrwx 1 root root 0 Mar 15 23:04 card0 -> ../../devices/platform/display-subsystem/drm/card0/
lrwxrwxrwx 1 root root 0 Mar 15 23:04 card0-HDMI-A-1 -> ../../devices/platform/display-subsystem/drm/card0/card0-HDMI-A-1/
lrwxrwxrwx 1 root root 0 Mar 15 23:04 card1 -> ../../devices/platform/ff9a0000.gpu/drm/card1/
lrwxrwxrwx 1 root root 0 Mar 15 23:04 renderD128 -> ../../devices/platform/ff9a0000.gpu/drm/renderD128/
-r--r--r-- 1 root root 4096 Mar 15 23:04 version
其中card0-HDMI-A-1代表的是hdmi显示设备，由于这是一个链接文件，查看card0-HDMI-A-1目录结构；
root@rk3399:~# ll /sys/class/drm/card0-HDMI-A-1/
lrwxrwxrwx 1 root root 0 Mar 15 23:14 ddc -> ../../../../ff160000.i2c/i2c-7/
lrwxrwxrwx 1 root root 0 Mar 15 23:14 device -> ../../card0/
-r--r--r-- 1 root root 4096 Mar 15 23:14 dpms
-r--r--r-- 1 root root 0 Mar 15 23:14 edid
-r--r--r-- 1 root root 4096 Mar 15 23:04 enabled
-r--r--r-- 1 root root 4096 Mar 15 23:14 modes
drwxr-xr-x 2 root root 0 Mar 15 23:14 power/
-rw-r--r-- 1 root root 4096 Mar 15 23:04 status
lrwxrwxrwx 1 root root 0 Mar 15 23:04 subsystem -> ../../../../../../class/drm/
-rw-r--r-- 1 root root 4096 Mar 15 23:04 uevent
其中：
ddc：hdmi显示数据通道，指向i2c7，用来获取edid、hdcp密钥等内容；device：指向card0；edid：存储hdmi显示器的扩展显示标识数据；enabled：hdmi接口是否被启用或禁用；modes：连接的hdmi显示器以及当前hdmi控制器同时支持的分辨率列表；status：hdmi接口连接状态的信息；
5.2.2 drm_debugfs_connector_add
drm_debugfs_connector_add函数位于drivers/gpu/drm/drm_debugfs.c，这段代码是关于DRM子系统中的debugfs接口的实现。主要作用是在debugfs中添加connector的调试文件，以便进行调试和诊断。
static const struct file_operations drm_edid_fops = {
.owner = THIS_MODULE,
.open = edid_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
.write = edid_write
};
static const struct file_operations drm_connector_fops = {
.owner = THIS_MODULE,
.open = connector_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
.write = connector_write
};
void drm_debugfs_connector_add(struct drm_connector *connector)
{
// 获取drm_device中存储的primary
struct drm_minor *minor = connector->dev->primary;
struct dentry *root;
// 检查是否存在 debugfs_root
if (!minor->debugfs_root)
return;
// 在minor->debugfs_root根目录下（即/sys/kernel/debug/dri/%d）创建一个与connector名称对应的目录
root = debugfs_create_dir(connector->name, minor->debugfs_root);
connector->debugfs_entry = root;
/* force */
debugfs_create_file("force", 0644, root, connector,
&drm_connector_fops);
/* edid */
debugfs_create_file("edid_override", 0644, root, connector,
&drm_edid_fops);
/* vrr range */
debugfs_create_file("vrr_range", 0444, root, connector,
&vrr_range_fops);
/* max bpc */
debugfs_create_file("output_bpc", 0444, root, connector,
&output_bpc_fops);
if (connector->funcs->debugfs_init)
connector->funcs->debugfs_init(connector, root);
}
以HDMI驱动为例，其会完成connector以及encoder的初始化和注册，因此我们可以在debugfs文件系统看到：
root@rk3399:~# ll /sys/kernel/debug/dri/
drwxr-xr-x 5 root root 0 Jan 1 1970 0/
drwxr-xr-x 2 root root 0 Jan 1 1970 1/
drwxr-xr-x 2 root root 0 Jan 1 1970 128/
root@rk3399:~# ll /sys/kernel/debug/dri/0/
drwxr-xr-x 2 root root 0 Jan 1 1970 HDMI-A-1/
-r--r--r-- 1 root root 0 Jan 1 1970 clients
drwxr-xr-x 3 root root 0 Jan 1 1970 crtc-0/
drwxr-xr-x 3 root root 0 Jan 1 1970 crtc-1/
-r--r--r-- 1 root root 0 Jan 1 1970 framebuffer
-r--r--r-- 1 root root 0 Jan 1 1970 gem_names
-r--r--r-- 1 root root 0 Jan 1 1970 internal_clients
-r--r--r-- 1 root root 0 Jan 1 1970 name
-r--r--r-- 1 root root 0 Jan 1 1970 state
root@rk3399:~# ll /sys/kernel/debug/dri/0/HDMI-A-1/
total 0
drwxr-xr-x 2 root root 0 Jan 1 1970 ./
drwxr-xr-x 5 root root 0 Jan 1 1970 ../
-rw-r--r-- 1 root root 0 Jan 1 1970 edid_override
-rw-r--r-- 1 root root 0 Jan 1 1970 force
-r--r--r-- 1 root root 0 Jan 1 1970 output_bpc
-r--r--r-- 1 root root 0 Jan 1 1970 vrr_range
其中/sys/kernel/debug/dri/0/HDMI-A-1/目录就是由drm_debugfs_connector_add创建完成的，其中包含了edid_override、force、output_bpc、vrr_range四个文件。
参考文章
[1] RK3399驱动开发 | 20 - 阿美林7寸mipi屏幕调试
