linux kernel 平台总线实例分析
linux 平台总线的实现有三大块 ， platform bus , platform device , platform drvice
平台类型结构体:
1 2 /** 3 * struct bus_type - The bus type of the device 4 * 5 * @name: The name of the bus. 6 * @bus_attrs: Default attributes of the bus. 7 * @dev_attrs: Default attributes of the devices on the bus. 8 * @drv_attrs: Default attributes of the device drivers on the bus. 9 * @match: Called, perhaps multiple times, whenever a new device or driver 10 * is added for this bus. It should return a nonzero value if the 11 * given device can be handled by the given driver. 12 * @uevent: Called when a device is added, removed, or a few other things 13 * that generate uevents to add the environment variables. 14 * @probe: Called when a new device or driver add to this bus, and callback 15 * the specific driver's probe to initial the matched device. 16 * @remove: Called when a device removed from this bus. 17 * @shutdown: Called at shut-down time to quiesce the device. 18 * @suspend: Called when a device on this bus wants to go to sleep mode. 19 * @resume: Called to bring a device on this bus out of sleep mode. 20 * @pm: Power management operations of this bus, callback the specific 21 * device driver's pm-ops. 22 * @p: The private data of the driver core, only the driver core can 23 * touch this. 24 * 25 * A bus is a channel between the processor and one or more devices. For the 26 * purposes of the device model, all devices are connected via a bus, even if 27 * it is an internal, virtual, "platform" bus. Buses can plug into each other. 28 * A USB controller is usually a PCI device, for example. The device model 29 * represents the actual connections between buses and the devices they control. 30 * A bus is represented by the bus_type structure. It contains the name, the 31 * default attributes, the bus' methods, PM operations, and the driver core's 32 * private data. 33 */
1 struct bus_type { 2 const char *name; 3 struct bus_attribute *bus_attrs; // 总线属性 4 struct device_attribute *dev_attrs; // 设备属性 5 struct driver_attribute *drv_attrs; // 驱动性 6 int (*match)(struct device *dev, struct device_driver *drv); //匹配平台设备与平台驱动的函数 7 int (*uevent)(struct device *dev, struct kobj_uevent_env *env); 8 int (*probe)(struct device *dev); 9 int (*remove)(struct device *dev); 10 void (*shutdown)(struct device *dev); 11 12 int (*suspend)(struct device *dev, pm_message_t state); 13 int (*resume)(struct device *dev); 14 15 const struct dev_pm_ops *pm; 16 17 struct subsys_private *p; 18 };
参考： http://blog.chinaunix.net/uid-25622207-id-2778126.html
在kernel中 ， 首先是有platform bus被kernel 注册
有以下流程：
init/main.c
1 static int __init kernel_init(void * unused) 2 { 3 ...... 4 do_basic_setup(); 5 ...... 6 } 7 8 //再到 9 static void __init do_basic_setup(void) 10 { 11 cpuset_init_smp(); 12 usermodehelper_init(); 13 init_tmpfs(); 14 driver_init(); 15 init_irq_proc(); 16 do_ctors(); 17 do_initcalls(); 18 }
再进 driver_init()
1 void __init driver_init(void) 2 { 3 /* These are the core pieces */ 4 devtmpfs_init(); 5 devices_init(); 6 buses_init(); 7 classes_init(); 8 firmware_init(); 9 hypervisor_init(); 10 11 /* These are also core pieces, but must come after the 12 * core core pieces. 13 */ 14 platform_bus_init(); //平台总线初始化 15 system_bus_init(); 16 cpu_dev_init(); 17 memory_dev_init(); 18 }
再进平台总线初始化
1 struct device platform_bus = { 2 .init_name = "platform", 3 }; 4 EXPORT_SYMBOL_GPL(platform_bus); 5 //... 6 7 struct bus_type platform_bus_type = { 8 .name = "platform", 9 .dev_attrs = platform_dev_attrs, 10 .match = platform_match, 11 .uevent = platform_uevent, 12 .pm = &platform_dev_pm_ops, 13 }; 14 EXPORT_SYMBOL_GPL(platform_bus_type); 15 16 //... 17 int __init platform_bus_init(void) 18 { 19 int error; 20 21 early_platform_cleanup(); 22 23 error = device_register(&platform_bus); //将平台总线作为一个设备注册 24 if (error) 25 return error; 26 error = bus_register(&platform_bus_type); 27 if (error) 28 device_unregister(&platform_bus); 29 return error; 30 }
match 函数是等下匹配platform device 和 platform driver 的函数
1 /**
2 * platform_match - bind platform device to platform driver.
3 * @dev: device.
4 * @drv: driver.
5 *
6 * Platform device IDs are assumed to be encoded like this:
7 * "<name><instance>", where <name> is a short description of the type of
8 * device, like "pci" or "floppy", and <instance> is the enumerated
9 * instance of the device, like '0' or '42'. Driver IDs are simply
10 * "<name>". So, extract the <name> from the platform_device structure,
11 * and compare it against the name of the driver. Return whether they match
12 * or not.
13 */
14
15 static int platform_match(struct device *dev, struct device_driver *drv)
16 {
17 struct platform_device *pdev = to_platform_device(dev);
18 struct platform_driver *pdrv = to_platform_driver(drv);
19
20 /* Attempt an OF style match first */
21 if (of_driver_match_device(dev, drv))
22 return 1;
23
24 /* Then try to match against the id table */
25 if (pdrv->id_table)
26 return platform_match_id(pdrv->id_table, pdev) != NULL;
27
28 /* fall-back to driver name match */
29 return (strcmp(pdev->name, drv->name) == 0);
30 }
//通过id_table 来匹配
1 static const struct platform_device_id *platform_match_id(
2 const struct platform_device_id *id,
3 struct platform_device *pdev)
4 {
5 while (id->name[0]) {
6 if (strcmp(pdev->name, id->name) == 0) {
7 pdev->id_entry = id;
8 return id;
9 }
10 id++;
11 }
12 return NULL;
13 }
1 int device_register(struct device *dev) 2 { 3 device_initialize(dev); 4 return device_add(dev); 5 }
此时platform bus 已经作为一个设备挂到内核上
看完平台总线， 下面看平台设备的注册流程：
还是得把一开始的platform device 结构体放到这里来：
1 2 struct platform_device { 3 const char * name; //平台设备名字 4 int id; 5 struct device dev; //设备结构体 6 u32 num_resources; //资源个数 7 struct resource * resource; //资源 8 9 const struct platform_device_id *id_entry; 10 11 /* MFD cell pointer */ 12 struct mfd_cell *mfd_cell; 13 14 /* arch specific additions */ 15 struct pdev_archdata archdata; 16 }; 17 18 #define platform_get_device_id(pdev) ((pdev)->id_entry) 19 //通过device 找到对应的platform_device 结构体 20 #define to_platform_device(x) container_of((x), struct platform_device, dev)
其实这里边还有个设备结构体 ， 他是依附在平台设备里面 1 /** 2 * struct device - The basic device structure 3 * @parent: The device's "parent" device, the device to which it is attached. 4 * In most cases, a parent device is some sort of bus or host 5 * controller. If parent is NULL, the device, is a top-level device, 6 * which is not usually what you want. 7 * @p: Holds the private data of the driver core portions of the device. 8 * See the comment of the struct device_private for detail. 9 * @kobj: A top-level, abstract class from which other classes are derived. 10 * @init_name: Initial name of the device. 11 * @type: The type of device. 12 * This identifies the device type and carries type-specific 13 * information. 14 * @mutex: Mutex to synchronize calls to its driver. 15 * @bus: Type of bus device is on. 16 * @driver: Which driver has allocated this 17 * @platform_data: Platform data specific to the device. 18 * Example: For devices on custom boards, as typical of embedded 19 * and SOC based hardware, Linux often uses platform_data to point 20 * to board-specific structures describing devices and how they 21 * are wired. That can include what ports are available, chip 22 * variants, which GPIO pins act in what additional roles, and so 23 * on. This shrinks the "Board Support Packages" (BSPs) and 24 * minimizes board-specific #ifdefs in drivers. 25 * @power: For device power management. 26 * See Documentation/power/devices.txt for details. 27 * @pwr_domain: Provide callbacks that are executed during system suspend, 28 * hibernation, system resume and during runtime PM transitions 29 * along with subsystem-level and driver-level callbacks. 30 * @numa_node: NUMA node this device is close to. 31 * @dma_mask: Dma mask (if dma'ble device). 32 * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all 33 * hardware supports 64-bit addresses for consistent allocations 34 * such descriptors. 35 * @dma_parms: A low level driver may set these to teach IOMMU code about 36 * segment limitations. 37 * @dma_pools: Dma pools (if dma'ble device). 38 * @dma_mem: Internal for coherent mem override. 39 * @archdata: For arch-specific additions. 40 * @of_node: Associated device tree node. 41 * @devt: For creating the sysfs "dev". 42 * @devres_lock: Spinlock to protect the resource of the device. 43 * @devres_head: The resources list of the device. 44 * @knode_class: The node used to add the device to the class list. 45 * @class: The class of the device. 46 * @groups: Optional attribute groups. 47 * @release: Callback to free the device after all references have 48 * gone away. This should be set by the allocator of the 49 * device (i.e. the bus driver that discovered the device). 50 * 51 * At the lowest level, every device in a Linux system is represented by an 52 * instance of struct device. The device structure contains the information 53 * that the device model core needs to model the system. Most subsystems, 54 * however, track additional information about the devices they host. As a 55 * result, it is rare for devices to be represented by bare device structures; 56 * instead, that structure, like kobject structures, is usually embedded within 57 * a higher-level representation of the device. 58 */ 1 struct device { 2 struct device *parent; // 设备的父类 3 4 struct device_private *p; //设备的私有数据 5 6 struct kobject kobj; 7 const char *init_name; /* initial name of the device */ 8 const struct device_type *type; 9 10 struct mutex mutex; /* mutex to synchronize calls to 11 * its driver. 12 */ 13 //表示该设备是属于哪一条总线 14 struct bus_type *bus; /* type of bus device is on */ 15 struct device_driver *driver; /* which driver has allocated this 16 device */ // 哪个驱动调用了这个设备 17 void *platform_data; /* Platform specific data, device 18 core doesn't touch it ***********/ 19 struct dev_pm_info power; 20 struct dev_power_domain *pwr_domain; 21 22 #ifdef CONFIG_NUMA 23 int numa_node; /* NUMA node this device is close to */ 24 #endif 25 u64 *dma_mask; /* dma mask (if dma'able device) */ 26 u64 coherent_dma_mask;/* Like dma_mask, but for 27 alloc_coherent mappings as 28 not all hardware supports 29 64 bit addresses for consistent 30 allocations such descriptors. */ 31 32 struct device_dma_parameters *dma_parms; 33 34 struct list_head dma_pools; /* dma pools (if dma'ble) */ 35 36 struct dma_coherent_mem *dma_mem; /* internal for coherent mem 37 override */ 38 /* arch specific additions */ 39 struct dev_archdata archdata; 40 41 struct device_node *of_node; /* associated device tree node */ 42 43 dev_t devt; /* dev_t, creates the sysfs "dev" */ //主次设备号的>结合体 44 45 spinlock_t devres_lock; 46 struct list_head devres_head; 47 48 struct klist_node knode_class; 49 struct class *class; 50 const struct attribute_group **groups; /* optional groups */ 51 52 void (*release)(struct device *dev); 53 };
1 //平台设备注册函数 2 extern int platform_device_register(struct platform_device *); 3 extern void platform_device_unregister(struct platform_device *); 4 //平台设备解注册函数
这两个函数对外发布
i2c 设备就用到了这个 函数进行 platform device 的 register
在arch/arm/mach-mx6/board-mx6q_sabresd.c 中
1 MACHINE_START(MX6Q_SABRESD, "Freescale i.MX 6Quad/DualLite/Solo Sabre-SD Board") /* Maintainer: Freescale Semiconductor, Inc. */ 2 .boot_params = MX6_PHYS_OFFSET + 0x100, 3 .fixup = fixup_mxc_board, 4 .map_io = mx6_map_io, 5 .init_irq = mx6_init_irq, 6 .init_machine = mx6_sabresd_board_init, // 板级的初始化 7 .timer = &mx6_sabresd_timer, // 时钟的初始化 8 .reserve = mx6q_sabresd_reserve, 9 MACHINE_END
时钟的话跟过去得到 i2c 的 CLK 的速度是400KB/s
在mx6_sabresd_board_init 中
平台设备内设备的平台数据进行赋值
1 static struct i2c_gpio_platform_data i2c_bus_gpio_data = { 2 .sda_pin = SABRESD_I2C4_SDA_GPIO, 3 .scl_pin = SABRESD_I2C4_SCL_GPIO, 4 .udelay = 10, //10Khz 5 .timeout = 500, 6 //.sda_is_open_drain = 1, //在当前板子上不能加 7 //.scl_is_open_drain = 1, //在当前板子上不能加 8 };
平台设备结构体的赋值
1 static struct platform_device i2c_bus_gpio_device = { 2 .name = "i2c-gpio", //这个名字是必须这样，主要是为了和i2c-gpio驱动对应 3 //由于板子已经用掉了0,1,2号，这里使用3 4 .id = 3, /* bus have 0,1,2, so start at 3 */ 5 .dev = { 6 .platform_data = &i2c_bus_gpio_data, 7 } 8 };
板级的初始化：
1 static void __init mx6_sabresd_board_init(void) 2 { 3 4 //。。。。。。 5 6 /** 7 * register gpio i2c bus write by zengjf 8 * 注册i2c-gpio设备，相当于注册一个I2C控制器 9 */ 10 platform_device_register(&i2c_bus_gpio_device); 11 12 i2c_register_board_info(0, mxc_i2c0_board_info, 13 ARRAY_SIZE(mxc_i2c0_board_info)); 14 i2c_register_board_info(1, mxc_i2c1_board_info, 15 ARRAY_SIZE(mxc_i2c1_board_info)); 16 i2c_register_board_info(2, mxc_i2c2_board_info, 17 ARRAY_SIZE(mxc_i2c2_board_info)); 18 /** 19 * register gpio i2c device write by zengjf 20 * 在I2C控制器3上注册I2C设备，这里的控制器3就是前面注册的I2C控制器， 21 * 主要是因为前面注册的I2C控制器的id是3 22 */ 23 i2c_register_board_info(3, gpio_i2c_devices, ARRAY_SIZE(gpio_i2c_devices)); 24 25 //。。。。。。 26 27 }
在mx6这块板子身上 ， i2c 0 , 1 , 2 是比较正常的i2c 总线， 但是i2c 3 是用的两个GPIO口模拟的 i2c 的SCL和 SDA线
下面 ， 跟进
1 platform_device_register(&i2c_bus_gpio_device);
/drivers/base/platform.c
1 /** 2 * platform_device_register - add a platform-level device 3 * @pdev: platform device we're adding 4 */ 5 int platform_device_register(struct platform_device *pdev) 6 { 7 device_initialize(&pdev->dev); //初始化设备 8 return platform_device_add(pdev); //平台设备添加 9 } 10 EXPORT_SYMBOL_GPL(platform_device_register);
跟进 platform_device_add(pdev)
1 /** 2 * platform_device_add - add a platform device to device hierarchy 3 * @pdev: platform device we're adding 4 * 5 * This is part 2 of platform_device_register(), though may be called 6 * separately _iff_ pdev was allocated by platform_device_alloc(). 7 */ 8 int platform_device_add(struct platform_device *pdev) 9 { 10 int i, ret = 0; 11 12 if (!pdev) 13 return -EINVAL; 14 15 if (!pdev->dev.parent) 16 pdev->dev.parent = &platform_bus; //属于平台总线, 17 18 pdev->dev.bus = &platform_bus_type; // 在platform_bus_init()的时候已经注册了平台总线类型 19 20 if (pdev->id != -1) 21 dev_set_name(&pdev->dev, "%s.%d", pdev->name, pdev->id); //pdev->dev 只有一个platform_data , pdev->name == i2c-gpio , pdev->id == 3 22 else 23 dev_set_name(&pdev->dev, "%s", pdev->name); 24 25 for (i = 0; i < pdev->num_resources; i++) { 26 struct resource *p, *r = &pdev->resource[i]; 27 28 if (r->name == NULL) 29 r->name = dev_name(&pdev->dev); 30 31 p = r->parent; 32 if (!p) { 33 if (resource_type(r) == IORESOURCE_MEM) 34 p = &iomem_resource; 35 else if (resource_type(r) == IORESOURCE_IO) 36 p = &ioport_resource; 37 } 38 39 if (p && insert_resource(p, r)) { 40 printk(KERN_ERR 41 "%s: failed to claim resource %d\n", 42 dev_name(&pdev->dev), i); 43 ret = -EBUSY; 44 goto failed; 45 } 46 } 47 48 pr_debug("Registering platform device '%s'. Parent at %s\n", 49 dev_name(&pdev->dev), dev_name(pdev->dev.parent)); 50 51 ret = device_add(&pdev->dev); //最终通过这里将设备挂到设备链表上 52 if (ret == 0) 53 return ret; 54 55 failed: 56 while (--i >= 0) { 57 struct resource *r = &pdev->resource[i]; 58 unsigned long type = resource_type(r); 59 60 if (type == IORESOURCE_MEM || type == IORESOURCE_IO) 61 release_resource(r); 62 } 63 64 return ret; 65 } 66 EXPORT_SYMBOL_GPL(platform_device_add);
最终 ，通过上面那个函数 注册一个平台设备 ， 我们自己也可以利用这个函数(platform_device_add) 去注册一个我们自己的平台设备 与我们自己本身的平台设备的驱动相匹配
相对应的 ， 有平台设备的注册就必然有平台设备的解除注册
1 /** 2 * platform_device_unregister - unregister a platform-level device 3 * @pdev: platform device we're unregistering 4 * 5 * Unregistration is done in 2 steps. First we release all resources 6 * and remove it from the subsystem, then we drop reference count by 7 * calling platform_device_put(). 8 */ 9 void platform_device_unregister(struct platform_device *pdev) 10 { 11 platform_device_del(pdev); 12 platform_device_put(pdev); 13 } 14 EXPORT_SYMBOL_GPL(platform_device_unregister);
从而得到我们平台设备的接触注册是调用了platform_device_del()
1 /** 2 * platform_device_del - remove a platform-level device 3 * @pdev: platform device we're removing 4 * 5 * Note that this function will also release all memory- and port-based 6 * resources owned by the device (@dev->resource). This function must 7 * _only_ be externally called in error cases. All other usage is a bug. 8 */ 9 void platform_device_del(struct platform_device *pdev) 10 { 11 int i; 12 13 if (pdev) { 14 device_del(&pdev->dev); //对应的是device_add , 该函数是设备删除 15 16 for (i = 0; i < pdev->num_resources; i++) { 17 struct resource *r = &pdev->resource[i]; 18 unsigned long type = resource_type(r); 19 20 if (type == IORESOURCE_MEM || type == IORESOURCE_IO) 21 release_resource(r); 22 } 23 } 24 } 25 EXPORT_SYMBOL_GPL(platform_device_del);
我们可以用这个函数对平台设备解除注册
下面就分析一下 ， i2c3 总线上 eeprom 这个设备驱动 ， 并分析他是怎么通过一系列相关的匹配 将平台总线 ， 平台设备， 平台设备驱动相关联（匹配）。
老样子 ， 先上两个结构体
平台驱动结构体：
1 struct platform_driver { 2 int (*probe)(struct platform_device *); //这个函数是一个真正的入口函数 ， 等下会分析 3 int (*remove)(struct platform_device *); 4 void (*shutdown)(struct platform_device *); 5 int (*suspend)(struct platform_device *, pm_message_t state); 6 int (*resume)(struct platform_device *); 7 struct device_driver driver; //设备驱动结构体 8 const struct platform_device_id *id_table; //平台设备id表 9 };
设备驱动结构体：
1
2 /**
3 * struct device_driver - The basic device driver structure
4 * @name: Name of the device driver.
5 * @bus: The bus which the device of this driver belongs to.
6 * @owner: The module owner.
7 * @mod_name: Used for built-in modules.
8 * @suppress_bind_attrs: Disables bind/unbind via sysfs.
9 * @of_match_table: The open firmware table.
10 * @probe: Called to query the existence of a specific device,
11 * whether this driver can work with it, and bind the driver
12 * to a specific device.
13 * @remove: Called when the device is removed from the system to
14 * unbind a device from this driver.
15 * @shutdown: Called at shut-down time to quiesce the device.
16 * @suspend: Called to put the device to sleep mode. Usually to a
17 * low power state.
18 * @resume: Called to bring a device from sleep mode.
19 * @groups: Default attributes that get created by the driver core
20 * automatically.
21 * @pm: Power management operations of the device which matched
22 * this driver.
23 * @p: Driver core's private data, no one other than the driver
24 * core can touch this.
25 *
26 * The device driver-model tracks all of the drivers known to the system.
27 * The main reason for this tracking is to enable the driver core to match
28 * up drivers with new devices. Once drivers are known objects within the
29 * system, however, a number of other things become possible. Device drivers
30 * can export information and configuration variables that are independent
31 * of any specific device.
32 */
1 struct device_driver {
2 const char *name; /* 设备驱动的名字 */
3 struct bus_type *bus; /* belong which bus (chenfl)*/
4
5 struct module *owner;
6 const char *mod_name; /* used for built-in modules */
7
8 bool suppress_bind_attrs; /* disables bind/unbind via sysfs */
9
10 const struct of_device_id *of_match_table;
11
12 int (*probe) (struct device *dev);
13 int (*remove) (struct device *dev);
14 void (*shutdown) (struct device *dev);
15 int (*suspend) (struct device *dev, pm_message_t state);
16 int (*resume) (struct device *dev);
17 const struct attribute_group **groups;
18
19 const struct dev_pm_ops *pm;
20
21
22 struct driver_private *p;
23 };
再介绍一个两个函数：
1 //平台设备驱动的注册函数 2 extern int platform_driver_register(struct platform_driver *); 3 extern void platform_driver_unregister(struct platform_driver *); 4 //平台设备驱动解除注册函数
等下会对这两个函数进行分析
了解完这两个结构体后来跟一个epprom 这个设备的驱动
如果是借鉴的就随意找一个平台设备驱动与之同理
drivers/misc/eeprom/at24.c:
1 static struct i2c_driver at24_driver = { 2 .driver = { 3 .name = "at24", 4 .owner = THIS_MODULE, 5 }, 6 .probe = at24_probe, 7 .remove = __devexit_p(at24_remove), 8 .id_table = at24_ids, 9 };
1 static int __init at24_init(void) 2 { 3 if (!io_limit) { 4 pr_err("at24: io_limit must not be 0!\n"); 5 return -EINVAL; 6 } 7 8 io_limit = rounddown_pow_of_two(io_limit); 9 return i2c_add_driver(&at24_driver); 10 } 11 module_init(at24_init);
1 static inline int i2c_add_driver(struct i2c_driver *driver) 2 { 3 return i2c_register_driver(THIS_MODULE, driver); 4 }
1 2 struct bus_type i2c_bus_type = { 3 .name = "i2c", 4 .match = i2c_device_match, 5 .probe = i2c_device_probe, 6 .remove = i2c_device_remove, 7 .shutdown = i2c_device_shutdown, 8 .pm = &i2c_device_pm_ops, 9 }; 10 EXPORT_SYMBOL_GPL(i2c_bus_type);
1 /* 2 * An i2c_driver is used with one or more i2c_client (device) nodes to access 3 * i2c slave chips, on a bus instance associated with some i2c_adapter. 4 */ 5 6 int i2c_register_driver(struct module *owner, struct i2c_driver *driver) 7 { 8 int res; 9 10 /* Can't register until after driver model init */ 11 if (unlikely(WARN_ON(!i2c_bus_type.p))) 12 return -EAGAIN; 13 14 /* add the driver to the list of i2c drivers in the driver core */ 15 driver->driver.owner = owner; 16 driver->driver.bus = &i2c_bus_type; 17 18 /* When registration returns, the driver core 19 * will have called probe() for all matching-but-unbound devices. 20 *///这里边有一个匹配成功并执行probe的过程 21 res = driver_register(&driver->driver); //drvier->driver == {.name = .name = "at24", .owner = THIS_MODULE, }
.owner = owner ,
.bus = &i2c_bus_type } 22 if (res) 23 return res; 24 25 /* Drivers should switch to dev_pm_ops instead. */ 26 if (driver->suspend) 27 pr_warn("i2c-core: driver [%s] using legacy suspend method\n", 28 driver->driver.name); 29 if (driver->resume) 30 pr_warn("i2c-core: driver [%s] using legacy resume method\n", 31 driver->driver.name); 32 33 pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name); 34 35 INIT_LIST_HEAD(&driver->clients); 36 /* Walk the adapters that are already present */ 37 i2c_for_each_dev(driver, __process_new_driver); 38 39 return 0; 40 } 41 EXPORT_SYMBOL(i2c_register_driver);
再进driver_register(struct device_driver *drv)
1 /** 2 * driver_register - register driver with bus 3 * @drv: driver to register 4 * 5 * We pass off most of the work to the bus_add_driver() call, 6 * since most of the things we have to do deal with the bus 7 * structures. 8 */ 9 int driver_register(struct device_driver *drv) 10 { 11 int ret; 12 struct device_driver *other; 13 14 BUG_ON(!drv->bus->p); 15 16 if ((drv->bus->probe && drv->probe) || 17 (drv->bus->remove && drv->remove) || 18 (drv->bus->shutdown && drv->shutdown)) 19 printk(KERN_WARNING "Driver '%s' needs updating - please use " 20 "bus_type methods\n", drv->name); 21 22 other = driver_find(drv->name, drv->bus); 23 if (other) { 24 put_driver(other); 25 printk(KERN_ERR "Error: Driver '%s' is already registered, " 26 "aborting...\n", drv->name); 27 return -EBUSY; 28 } 29 30 ret = bus_add_driver(drv); //再进！！！ 31 if (ret) 32 return ret; 33 ret = driver_add_groups(drv, drv->groups); 34 if (ret) 35 bus_remove_driver(drv); 36 return ret; 37 } 38 EXPORT_SYMBOL_GPL(driver_register); 39
再进bus_add_driver(drv)
1 /** 2 * bus_add_driver - Add a driver to the bus. 3 * @drv: driver. 4 */ 5 int bus_add_driver(struct device_driver *drv) 6 { 7 struct bus_type *bus; 8 struct driver_private *priv; 9 int error = 0; 10 11 bus = bus_get(drv->bus); 12 if (!bus) 13 return -EINVAL; 14 15 pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name); 16 17 priv = kzalloc(sizeof(*priv), GFP_KERNEL); 18 if (!priv) { 19 error = -ENOMEM; 20 goto out_put_bus; 21 } 22 klist_init(&priv->klist_devices, NULL, NULL); 23 //初始化设备链表，每一个与该驱动匹配的device都会添加到该链表下 24 priv->driver = drv; 25 drv->p = priv; 26 priv->kobj.kset = bus->p->drivers_kset; 27 //指向该驱动所属的kset 28 error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL, 29 "%s", drv->name); 30 //初始化kobject 并将kobject添加到其对应的kset 集合中 31 if (error) 32 goto out_unregister; 33 34 if (drv->bus->p->drivers_autoprobe) { 35 error = driver_attach(drv); // 这里是即将要 绑定设备 与 驱动 并调用probe 地方 36 if (error) 37 goto out_unregister; 38 } 39 klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers); 40 module_add_driver(drv->owner, drv); 41 42 error = driver_create_file(drv, &driver_attr_uevent); 43 if (error) { 44 printk(KERN_ERR "%s: uevent attr (%s) failed\n", 45 __func__, drv->name); 46 } 47 error = driver_add_attrs(bus, drv); 48 if (error) { 49 /* How the hell do we get out of this pickle? Give up */ 50 printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n", 51 __func__, drv->name); 52 } 53 54 if (!drv->suppress_bind_attrs) { 55 error = add_bind_files(drv); 56 if (error) { 57 /* Ditto */ 58 printk(KERN_ERR "%s: add_bind_files(%s) failed\n", 59 __func__, drv->name); 60 } 61 } 62 63 kobject_uevent(&priv->kobj, KOBJ_ADD); 64 return 0; 65 66 out_unregister: 67 kobject_put(&priv->kobj); 68 kfree(drv->p); 69 drv->p = NULL; 70 out_put_bus: 71 bus_put(bus); 72 return error; 73 }
1 /** 2 * driver_attach - try to bind driver to devices. 3 * @drv: driver. 4 * 5 * Walk the list of devices that the bus has on it and try to 6 * match the driver with each one. If driver_probe_device() 7 * returns 0 and the @dev->driver is set, we've found a 8 * compatible pair. 9 */ 10 int driver_attach(struct device_driver *drv) 11 { 12 return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach); 13 // __将driver_atttach 传去进 14 //将每一个查找得到的device进行驱动匹配 15 } 16 EXPORT_SYMBOL_GPL(driver_attach);
1 /** 2 * bus_for_each_dev - device iterator. 3 * @bus: bus type. 4 * @start: device to start iterating from. 5 * @data: data for the callback. 6 * @fn: function to be called for each device. 7 * 8 * Iterate over @bus's list of devices, and call @fn for each, 9 * passing it @data. If @start is not NULL, we use that device to 10 * begin iterating from. 11 * 12 * We check the return of @fn each time. If it returns anything 13 * other than 0, we break out and return that value. 14 * 15 * NOTE: The device that returns a non-zero value is not retained 16 * in any way, nor is its refcount incremented. If the caller needs 17 * to retain this data, it should do so, and increment the reference 18 * count in the supplied callback. 19 */ 20 int bus_for_each_dev(struct bus_type *bus, struct device *start, 21 void *data, int (*fn)(struct device *, void *)) 22 { 23 struct klist_iter i; 24 struct device *dev; 25 int error = 0; 26 27 if (!bus) 28 return -EINVAL; 29 30 klist_iter_init_node(&bus->p->klist_devices, &i, 31 (start ? &start->p->knode_bus : NULL)); 32 while ((dev = next_device(&i)) && !error) 33 error = fn(dev, data); // 就是这个东西！！！ 34 klist_iter_exit(&i); 35 return error; 36 } 37 EXPORT_SYMBOL_GPL(bus_for_each_dev);
这里边 ， 调用了fn这个函数 ， fn 就是上面传进去的__driver_attach 函数
然后 ， 便有了
1 static int __driver_attach(struct device *dev, void *data) 2 { 3 struct device_driver *drv = data; 4 5 /* 6 * Lock device and try to bind to it. We drop the error 7 * here and always return 0, because we need to keep trying 8 * to bind to devices and some drivers will return an error 9 * simply if it didn't support the device. 10 * 11 * driver_probe_device() will spit a warning if there 12 * is an error. 13 */ 14 15 if (!driver_match_device(drv, dev)) 16 return 0; 17 18 if (dev->parent) /* Needed for USB */ 19 device_lock(dev->parent); 20 device_lock(dev); 21 if (!dev->driver) 22 driver_probe_device(drv, dev); //如果此时设备上所挂的驱动为空 ， 就进去 23 device_unlock(dev); 24 if (dev->parent) 25 device_unlock(dev->parent); 26 27 return 0; 28 }
然后就有了
1 /** 2 * driver_probe_device - attempt to bind device & driver together 3 * @drv: driver to bind a device to 4 * @dev: device to try to bind to the driver 5 * 6 * This function returns -ENODEV if the device is not registered, 7 * 1 if the device is bound successfully and 0 otherwise. 8 * 9 * This function must be called with @dev lock held. When called for a 10 * USB interface, @dev->parent lock must be held as well. 11 */ 12 int driver_probe_device(struct device_driver *drv, struct device *dev) 13 { 14 int ret = 0; 15 16 if (!device_is_registered(dev)) 17 return -ENODEV; 18 19 pr_debug("bus: '%s': %s: matched device %s with driver %s\n", 20 drv->bus->name, __func__, dev_name(dev), drv->name); 21 22 pm_runtime_get_noresume(dev); 23 pm_runtime_barrier(dev); 24 ret = really_probe(dev, drv); //这里！！！ 25 pm_runtime_put_sync(dev); 26 27 return ret; 28 }
bind device and driver , run probe
1 static int really_probe(struct device *dev, struct device_driver *drv) 2 { 3 int ret = 0; 4 5 atomic_inc(&probe_count); 6 pr_debug("bus: '%s': %s: probing driver %s with device %s\n", 7 drv->bus->name, __func__, drv->name, dev_name(dev)); 8 WARN_ON(!list_empty(&dev->devres_head)); 9 10 dev->driver = drv; //设备上的驱动设置为driver 11 if (driver_sysfs_add(dev)) { 12 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n", 13 __func__, dev_name(dev)); 14 goto probe_failed; 15 } 16 17 if (dev->bus->probe) { 18 ret = dev->bus->probe(dev); //如果总线上有probe , 就运行这个 19 if (ret) 20 goto probe_failed; 21 } else if (drv->probe) { 22 ret = drv->probe(dev); //这里边在driver 注册的时候 ， 已经给i2c_driver 里面的driver 结构体里边的bus 进行初始化赋值 23 if (ret) 24 goto probe_failed; 25 } 26 27 driver_bound(dev); 28 ret = 1; 29 pr_debug("bus: '%s': %s: bound device %s to driver %s\n", 30 drv->bus->name, __func__, dev_name(dev), drv->name); 31 goto done; 32 33 probe_failed: 34 devres_release_all(dev); 35 driver_sysfs_remove(dev); 36 dev->driver = NULL; 37 38 if (ret != -ENODEV && ret != -ENXIO) { 39 /* driver matched but the probe failed */ 40 printk(KERN_WARNING 41 "%s: probe of %s failed with error %d\n", 42 drv->name, dev_name(dev), ret); 43 } 44 /* 45 * Ignore errors returned by ->probe so that the next driver can try 46 * its luck. 47 */ 48 ret = 0; 49 done: 50 atomic_dec(&probe_count); 51 wake_up(&probe_waitqueue); 52 return ret; 53 }
上面22 行 ， 有如下分析代码：
1 struct bus_type i2c_bus_type = { 2 .name = "i2c", 3 .match = i2c_device_match, 4 .probe = i2c_device_probe, 5 .remove = i2c_device_remove, 6 .shutdown = i2c_device_shutdown, 7 .pm = &i2c_device_pm_ops, 8 }; 9 EXPORT_SYMBOL_GPL(i2c_bus_type);
1 int i2c_register_driver(struct module *owner, struct i2c_driver *driver) 2 { 3 ...... 4 /* add the driver to the list of i2c drivers in the driver core */ 5 driver->driver.owner = owner; 6 driver->driver.bus = &i2c_bus_type; 7 ...... 8 }
所以 ， 驱动与设备绑定之后 ， 运行的probe 是i2c_device_probe
1 static int i2c_device_probe(struct device *dev) 2 { 3 struct i2c_client *client = i2c_verify_client(dev); 4 struct i2c_driver *driver; 5 int status; 6 7 if (!client) 8 return 0; 9 10 driver = to_i2c_driver(dev->driver); 11 if (!driver->probe || !driver->id_table) 12 return -ENODEV; 13 client->driver = driver; 14 if (!device_can_wakeup(&client->dev)) 15 device_init_wakeup(&client->dev, 16 client->flags & I2C_CLIENT_WAKE); 17 dev_dbg(dev, "probe\n"); 18 19 status = driver->probe(client, i2c_match_id(driver->id_table, client)); 20 if (status) { 21 client->driver = NULL; 22 i2c_set_clientdata(client, NULL); 23 } 24 return status; 25 }
Read The Fucking Source Code
