在驱动模型的基础上，就可以构建实际的设备驱动了，这里以platform总线来进行介绍，因为platform总线具有代表性，platform不是一个实际的总线，它是虚拟出来的，所以在设备上的任何硬件驱动都可以挂在这条总线上，最典型的就是设备上的控制器模块都是挂在platform总线上的

1. platform总线注册

1.1 platform_bus_type

struct bus_type platform_bus_type = { .name = "platform", .dev_groups = platform_dev_groups, .match = platform_match, .uevent = platform_uevent, .pm = &platform_dev_pm_ops, };

1.2 platform总线注册

在系统初始化的时候会进行总线的注册

（drivers/base/platform.c）

int __init platform_bus_init(void) { int error; early_platform_cleanup(); error = device_register(&platform_bus);-----------platform作为设备注册 if (error) return error; error = bus_register(&platform_bus_type);--------platform总线注册 if (error) device_unregister(&platform_bus); of_platform_register_reconfig_notifier(); return error; }

2. platform设备注册

2.1 struct platform_device

（include/linux/platform_device.h）

struct platform_device { const char *name;---------------------设备名字 int id;----------------------------设备ID bool id_auto; struct device dev;-------------------嵌入的device结构体 u32 num_resources;-----------------设备资源数 struct resource *resource;-------------设备资源 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; };

2.2 platform_device_register

platform设备注册的函数为：

（include/linux/platform_device.h）

extern int platform_device_register(struct platform_device *);

该函数首先把platform_device添加到/sys/device目录下，真正的注册在下面函数中：

（drivers/base/platform.c）

int platform_device_add(struct platform_device *pdev) { int i, ret; if (!pdev) return -EINVAL; if (!pdev->dev.parent) pdev->dev.parent = &platform_bus;---------设置父设备为platform_bus pdev->dev.bus = &platform_bus_type;-----------所属总线为platform_bus switch (pdev->id) { 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; }---------------------------------------------设置name for (i = 0; i < pdev->num_resources; i++) { 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);-------------------device注册 if (ret == 0) return ret; ...... }

3. platform驱动注册

3.1 struct platform_driver

（include/linux/platform_device.h）

struct platform_driver { int (*probe)(struct platform_device *);----------驱动初始化 int (*remove)(struct platform_device *);---------驱动卸载 void (*shutdown)(struct platform_device *); int (*suspend)(struct platform_device *, pm_message_t state); int (*resume)(struct platform_device *); struct device_driver driver;---------------------嵌入的device_driver结构体 const struct platform_device_id *id_table; bool prevent_deferred_probe; };

3.2 设备驱动注册

（include/linux/platform_device.h）

#define platform_driver_register(drv) \ __platform_driver_register(drv, THIS_MODULE) int __platform_driver_register(struct platform_driver *drv, struct module *owner) { drv->driver.owner = owner; drv->driver.bus = &platform_bus_type;-------------所属总线为platform_bus drv->driver.probe = platform_drv_probe; drv->driver.remove = platform_drv_remove; drv->driver.shutdown = platform_drv_shutdown; return driver_register(&drv->driver);-------------驱动注册 }

最主要的来看下驱动初始化函数platform_drv_probe

static int platform_drv_probe(struct device *_dev) { struct platform_driver *drv = to_platform_driver(_dev->driver); struct platform_device *dev = to_platform_device(_dev); int ret; ret = of_clk_set_defaults(_dev->of_node, false); if (ret < 0) return ret; ret = dev_pm_domain_attach(_dev, true); if (ret != -EPROBE_DEFER) { if (drv->probe) { ret = drv->probe(dev);-----------------调用到具体设备的初始化函数probe if (ret) dev_pm_domain_detach(_dev, true); } else { /* don't fail if just dev_pm_domain_attach failed */ ret = 0; } } if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) { dev_warn(_dev, "probe deferral not supported\n"); ret = -ENXIO; } return ret; }