Platform device/driver注册过程 |
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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。 |
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