Platform device/driver注册过程
Platform是一种虚拟总线,Platform机制将设备本身的资源注册进内核,有内核统一管理,在驱动程序使用这些资源时使用统一的接口,这样提高了程序的可移植性。
Linux的大部分设备驱动都可以使用platform 机制,用platform device 表示设备,用platform driver 表示驱动。
Platform总线的定义如下:
struct bus_type platform_bus_type = {
.name = "platform",//总线名字,总线注册后新建目录sys/bus/platform
.dev_groups = platform_dev_groups,
.match = platform_match,//当有总线或者设备注册到platform总线时,内核自动调用match函数,判断设备和驱动的name是否一致。
.uevent = platform_uevent,
.pm = &platform_dev_pm_ops,
};
Platform device定义如下:
struct platform_device {
const char *name;//device名字,应该与platform driver对应。注册后,会在/sys/device/目录下创建一个以name命名的目录,并且创建软连接到/sys/bus/platform/device下。
int id;
bool id_auto;
struct device dev;//基本的device结构
u32 num_resources;//资源数
struct resource *resource;//资源
const struct platform_device_id *id_entry;
char *driver_override; /* Driver name to force a match */
/* MFD cell pointer */
struct mfd_cell *mfd_cell;
/* arch specific additions */
struct pdev_archdata archdata;
};
Platform driver定义如下:
struct platform_driver {
int (*probe)(struct platform_device *);//platform driver注册时,如果总线上已有匹配的device,将调用probe函数。
int (*remove)(struct platform_device *);
void (*shutdown)(struct platform_device *);
int (*suspend)(struct platform_device *, pm_message_t state);
int (*resume)(struct platform_device *);
struct device_driver driver;//基本的device driver结构.platform driver注册成功后,/sys/bus/platform/driver/目录下创建一个名字为driver->name的目录
const struct platform_device_id *id_table;
bool prevent_deferred_probe;
};
Platform device 注册过程:
int platform_device_register(struct platform_device *pdev)
{
device_initialize(&pdev->dev);//初始化platform device结构体中的dev结构
arch_setup_pdev_archdata(pdev);
return platform_device_add(pdev);//add platform到platform bus.
}
int platform_device_add(struct platform_device *pdev)
{
int i, ret;
if (!pdev)
return -EINVAL;
if (!pdev->dev.parent)
pdev->dev.parent = &platform_bus;//dev的parent device为platform_bus
pdev->dev.bus = &platform_bus_type;//dev的bus 类型
switch (pdev->id) {//设置dev 名字。
default:
dev_set_name(&pdev->dev, "%s.%d", pdev->name, pdev->id);
break;
case PLATFORM_DEVID_NONE:
dev_set_name(&pdev->dev, "%s", pdev->name);
break;
case PLATFORM_DEVID_AUTO:
/*
* Automatically allocated device ID. We mark it as such so
* that we remember it must be freed, and we append a suffix
* to avoid namespace collision with explicit IDs.
*/
ret = ida_simple_get(&platform_devid_ida, 0, 0, GFP_KERNEL);
if (ret < 0)
goto err_out;
pdev->id = ret;
pdev->id_auto = true;
dev_set_name(&pdev->dev, "%s.%d.auto", pdev->name, pdev->id);
break;
}
for (i = 0; i < pdev->num_resources; i++) {//添加resource
struct resource *p, *r = &pdev->resource[i];
if (r->name == NULL)
r->name = dev_name(&pdev->dev);
p = r->parent;
if (!p) {
if (resource_type(r) == IORESOURCE_MEM)
p = &iomem_resource;
else if (resource_type(r) == IORESOURCE_IO)
p = &ioport_resource;
}
if (p && insert_resource(p, r)) {
dev_err(&pdev->dev, "failed to claim resource %d\n", i);
ret = -EBUSY;
goto failed;
}
}
pr_debug("Registering platform device '%s'. Parent at %s\n",
dev_name(&pdev->dev), dev_name(pdev->dev.parent));
ret = device_add(&pdev->dev);//add dev到bus
if (ret == 0)
return ret;
failed:
if (pdev->id_auto) {
ida_simple_remove(&platform_devid_ida, pdev->id);
pdev->id = PLATFORM_DEVID_AUTO;
}
while (--i >= 0) {
struct resource *r = &pdev->resource[i];
if (r->parent)
release_resource(r);
}
err_out:
return ret;
}
在device_add函数中调用bus_add_device函数将device加到bus,并调用bus_probe_device来调用总线上与之匹配的driver的probe函数。
在bus_probe_device函数中主要调用device_initial_probe,
void device_initial_probe(struct device *dev)
{
__device_attach(dev, true);
}
在__device_attach中主要的代码如下:
ret = bus_for_each_drv(dev->bus, NULL, &data,
__device_attach_driver);//遍历总线上的driver,并调用__device_attach_driver
在__device_attach_driver中主要调用driver_match_device判断driver和device是否match,如果match则调用driver_probe_device来probe driver
static inline int driver_match_device(struct device_driver *drv,
struct device *dev)
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1;//drv所属bus的match函数。
}
bus->match即platform bus的match 函数:
static int platform_match(struct device *dev, struct device_driver *drv)
{
struct platform_device *pdev = to_platform_device(dev);
struct platform_driver *pdrv = to_platform_driver(drv);
/* When driver_override is set, only bind to the matching driver */
if (pdev->driver_override)
return !strcmp(pdev->driver_override, drv->name);
/* Attempt an OF style match first */
if (of_driver_match_device(dev, drv))
return 1;
/* Then try ACPI style match */
if (acpi_driver_match_device(dev, drv))
return 1;
/* Then try to match against the id table */
if (pdrv->id_table)
return platform_match_id(pdrv->id_table, pdev) != NULL;
/* fall-back to driver name match */
return (strcmp(pdev->name, drv->name) == 0);//比较driver和device的名字。
}
在driver_probe_device中主要调用really_probe,really_probe的主要代码如下。
if (dev->bus->probe) {//如果bus定义了probe,就调用bus的probe
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) {//调用bus所属driver的probe函数。
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}
Platform driver的注册过程:
int __platform_driver_register(struct platform_driver *drv,
struct module *owner)
{
drv->driver.owner = owner;
drv->driver.bus = &platform_bus_type;//driver的bus type为Platform bus
drv->driver.probe = platform_drv_probe;//driver的probe函数,如果platform driver定义了probe函数,里面调用的platform定义的probe
drv->driver.remove = platform_drv_remove;
drv->driver.shutdown = platform_drv_shutdown;
return driver_register(&drv->driver);//主要注册函数。
}
在driver_register函数中,通过driver_find查找driver是否已经注册,如果没有注册,则调用bus_add_driver将driver add到bus。
在bus_add_driver最主要的操作是driver 和匹配的device进行绑定。
int driver_attach(struct device_driver *drv)
{
return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);//遍历bus上所有的device,并调用__driver_attach
}
在__driver_attach函数中与上面__device_attach_driver过程类似,调用driver_match_device判断driver和device是否match,如果match则调用driver_probe_device来probe driver。如果bus上没有注册过与platform driver匹配的platform device,那platform driver的probe函数将不会调用到。
从上述注册过程可以看出platform device和platform driver注册并不需要区分先后。
设备挂接到总线上时,与总线上的所有驱动进行匹配(用bus_type.match进行匹配)。如果匹配成功,则调用bus_type.probe或者driver.probe初始化该设备;挂接到总线上如果匹配失败,则只是将该设备挂接到总线上。
驱动挂接到总线上时,与总线上的所有设备进行匹配(用bus_type.match进行匹配)。如果匹配成功,则调用bus_type.probe或者driver.probe初始化该设备;挂接到总线上如果匹配失败,则只是将该驱动挂接到总线上。