Linux gadget驱动分析1------驱动加载过程

　　为了解决一个问题,简单看了一遍linux gadget驱动的加载流程.做一下记录.

　　使用的内核为linux 2.6.35 硬件为芯唐NUC950. gadget是在UDC驱动上面的一层,如果要编写gadget驱动只需调用linux 的gadget API,不需设计底层的UDC驱动. 但要是分析驱动BUG,就需要了同时了解一下UDC.

　　下面以简单的gadget zero驱动分析驱动的加载流程.

　　主要是一系列的bind的调用,让gadget驱动一步步与硬件的端点联系起来.

　　从insmod g_zero.ko开始.

zero.c

 static struct usb_composite_driver zero_driver = {
     .name        = "zero",
     .dev        = &device_desc,
     .strings    = dev_strings,
     .bind        = zero_bind,
     .unbind        = zero_unbind,
     .suspend    = zero_suspend,
     .resume        = zero_resume,
 };

这个结构体是zero.c中的,如果是自己写的gadget驱动,这个结构体及这些函数需要自己实现.

先不去细看结构体中的具体内容,现在只关注注册流程.

 static int __init init(void)
 {
     return usb_composite_register(&zero_driver);
 }

调用
usb_composite_register(&zero_driver);

zero_driver作为参数传递,类型为struct usb_composite_driver

composite.c

int usb_composite_register(struct usb_composite_driver *driver)//zero_driver
{
    if (!driver || !driver->dev || !driver->bind || composite)
        return -EINVAL;
 
    if (!driver->name)
        driver->name = "composite";
    composite_driver.function =  (char *) driver->name;
    composite_driver.driver.name = driver->name;
    composite = driver;
 
    return usb_gadget_register_driver(&composite_driver);
}

composite_driver定义在composite.c中

 static struct usb_gadget_driver composite_driver = {
     .speed        = USB_SPEED_HIGH,
 
     .bind        = composite_bind,
     .unbind        = composite_unbind,
 
     .setup        = composite_setup,
     .disconnect    = composite_disconnect,
 
     .suspend    = composite_suspend,
     .resume        = composite_resume,
 
     .driver    = {
         .owner        = THIS_MODULE,
     },
 };

composite = driver;

用全局指针指向zero_driver,后面用到compoite这个指针时候知道它的值在这里赋好了.

最后调用usb_gadget_register_driver(&composite_driver);

不同的芯片实现不同,但原理应该类似,一般在xxx_udc.c中

nuc950在nuc900_udc.c中:

 int usb_gadget_register_driver (struct usb_gadget_driver *driver)
 {
         struct nuc900_udc *udc = &controller;
         int retval;
 
         printk("usb_gadget_register_driver() '%s'\n", driver->driver.name);
 
         if (!udc)
                 return -ENODEV;
 
         if (udc->driver)
                 return -EBUSY;
         if (!driver->bind || !driver->unbind || !driver->setup
                         || driver->speed == USB_SPEED_UNKNOWN)
                 return -EINVAL;
         printk("driver->speed=%d\n", driver->speed);
         udc->gadget.name = gadget_name;
         udc->gadget.ops = &nuc900_ops;
         udc->gadget.is_dualspeed = ;
         udc->gadget.speed = USB_SPEED_HIGH;//USB_SPEED_FULL;
         udc->ep0state = EP0_IDLE;
 
         udc->gadget.dev.release = nop_release;
 
         udc->driver = driver;
 
         udc->gadget.dev.driver = &driver->driver;
 
         printk( "binding gadget driver '%s'\n", driver->driver.name);
         if ((retval = driver->bind (&udc->gadget)) != ) {
                 printk("bind fail\n");
                 udc->driver = ;
                 udc->gadget.dev.driver = ;
                 return retval;
         }
         printk( "after driver bind:%p\n" , driver->bind);
 
         mdelay();
         __raw_writel(__raw_readl(REG_PWRON) | 0x400, REG_PWRON);//power on usb D+ high
 
         return ;
 }

controller是udc中很重要的一个变量,结构为

 struct nuc900_udc {
         spinlock_t            lock;
 
         struct nuc900_ep        ep[NUC900_ENDPOINTS];
         struct usb_gadget        gadget;
         struct usb_gadget_driver    *driver;
         struct platform_device        *pdev;
 
         struct clk                      *clk;
         struct resource                 *res;
         void __iomem                    *reg;
         int                             irq;
 
         enum ep0_state                     ep0state;
 
         u8                usb_devstate;
         u8                usb_address;
 
         u8                usb_dma_dir;
 
         u8                usb_dma_trigger;//bool. dma triggered
         u8                usb_dma_trigger_next;//need trigger again
         u8                usb_less_mps;
         u32                usb_dma_cnt;//one dma transfer count
         u32                usb_dma_loop;//for short packet only;dma loop, each loop 32byte;
         u32                     usb_dma_owner;
 
         struct usb_ctrlrequest            crq;
         s32                setup_ret;
 
         u32                             irq_enbl;
 };

这个结构中大部分不需要关注,需要关注的是第5行:

struct usb_gadget        gadget;
定义在gadget.h中,这linux标准的结构体:

 struct usb_gadget {
     /* readonly to gadget driver */
     const struct usb_gadget_ops    *ops;
     struct usb_ep            *ep0;
     struct list_head        ep_list;    /* of usb_ep */
     enum usb_device_speed        speed;
     unsigned            is_dualspeed:;
     unsigned            is_otg:;
     unsigned            is_a_peripheral:;
     unsigned            b_hnp_enable:;
     unsigned            a_hnp_support:;
     unsigned            a_alt_hnp_support:;
     const char            *name;
     struct device            dev;
 };

大致先扫一下这个结构,然后回到

usb_gadget_register_driver函数。

大体意思就是对上面的结构体进行了一番赋值，具体意义再回头看

然后在31行调用

if ((retval = driver->bind (&udc->gadget)) != 0)

第一个bind被调用了。

继续贴代码

 static int composite_bind(struct usb_gadget *gadget)
 {
     struct usb_composite_dev    *cdev;
     int                status = -ENOMEM;
 
     cdev = kzalloc(sizeof *cdev, GFP_KERNEL);
     if (!cdev)
         return status;
 
     spin_lock_init(&cdev->lock);
     cdev->gadget = gadget;
     set_gadget_data(gadget, cdev);
     INIT_LIST_HEAD(&cdev->configs);
 
     /* preallocate control response and buffer */
     cdev->req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
     if (!cdev->req)
         goto fail;
     cdev->req->buf = kmalloc(USB_BUFSIZ, GFP_KERNEL);
     if (!cdev->req->buf)
         goto fail;
     cdev->req->complete = composite_setup_complete;
     gadget->ep0->driver_data = cdev;
 
     cdev->bufsiz = USB_BUFSIZ;
     cdev->driver = composite;
 
     usb_gadget_set_selfpowered(gadget);
 
     /* interface and string IDs start at zero via kzalloc.
      * we force endpoints to start unassigned; few controller
      * drivers will zero ep->driver_data.
      */
     usb_ep_autoconfig_reset(cdev->gadget);
 
     /* standardized runtime overrides for device ID data */
     if (idVendor)
         cdev->desc.idVendor = cpu_to_le16(idVendor);
     if (idProduct)
         cdev->desc.idProduct = cpu_to_le16(idProduct);
     if (bcdDevice)
         cdev->desc.bcdDevice = cpu_to_le16(bcdDevice);
 
     /* composite gadget needs to assign strings for whole device (like
      * serial number), register function drivers, potentially update
      * power state and consumption, etc
      */
     status = composite->bind(cdev);
     if (status < )
         goto fail;
 
     cdev->desc = *composite->dev;
     cdev->desc.bMaxPacketSize0 = gadget->ep0->maxpacket;
 
     /* strings can't be assigned before bind() allocates the
      * releavnt identifiers
      */
     if (cdev->desc.iManufacturer && iManufacturer)
         string_override(composite->strings,
             cdev->desc.iManufacturer, iManufacturer);
     if (cdev->desc.iProduct && iProduct)
         string_override(composite->strings,
             cdev->desc.iProduct, iProduct);
     if (cdev->desc.iSerialNumber && iSerialNumber)
         string_override(composite->strings,
             cdev->desc.iSerialNumber, iSerialNumber);
 
     status = device_create_file(&gadget->dev, &dev_attr_suspended);
     if (status)
         goto fail;
 
     INFO(cdev, "%s ready\n", composite->name);
     return ;
 
 fail:
     composite_unbind(gadget);
     return status;
 }

还是简单分析

11~12行就是你中有我，我中有你

13行值得注意一下，初始化一个链表，config就是配置链表。

一个设备可能有多个配置

一个配置可能有多个接口

一个接口可能有多个端点或设置

15~23行 都与ep0这个控制端口有关，控制端口的相关内直接在设备bind的时候做也比较合理。

26行 cdev->driver = composite; //还记得composite指向的是谁，就是zero_driver

　这就bind好了吧。

直接看48行

status = composite->bind(cdev);

第二个bind被调用，

satic int __init zero_bind(struct usb_composite_dev *cdev)

这个函数需要关注的这几行

    if (loopdefault) {
        loopback_add(cdev, autoresume != );
        sourcesink_add(cdev, autoresume != );
    } else {
        sourcesink_add(cdev, autoresume != );
        loopback_add(cdev, autoresume != );
    }

应该就是gadget zero的两种配置 
sourcesink_add()在f_sourcesink.c中，是自己实现的

在此函数中调用

 return usb_add_config(cdev, &sourcesink_driver);

 static struct usb_configuration sourcesink_driver = {
     .label        = "source/sink",
     .strings    = sourcesink_strings,
     .bind        = sourcesink_bind_config,
     .setup        = sourcesink_setup,
     .bConfigurationValue = ,
     .bmAttributes    = USB_CONFIG_ATT_SELFPOWER,
     /* .iConfiguration = DYNAMIC */
 };

注意这个结构体中又出现一个bind

usb_add_config 在composite.c 中

 int usb_add_config(struct usb_composite_dev *cdev,
         struct usb_configuration *config)
 {
     int                status = -EINVAL;
     struct usb_configuration    *c;
 
     DBG(cdev, "adding config #%u '%s'/%p\n",
             config->bConfigurationValue,
             config->label, config);
 
     if (!config->bConfigurationValue || !config->bind)
         goto done;
 
     /* Prevent duplicate configuration identifiers */
     list_for_each_entry(c, &cdev->configs, list) {
         if (c->bConfigurationValue == config->bConfigurationValue) {
             status = -EBUSY;
             goto done;
         }
     }
 
     config->cdev = cdev;
     list_add_tail(&config->list, &cdev->configs);
 
     INIT_LIST_HEAD(&config->functions);
     config->next_interface_id = ;
 
     status = config->bind(config);
     if (status < ) {
         list_del(&config->list);
         config->cdev = NULL;
     } else {
         unsigned    i;
 
         DBG(cdev, "cfg %d/%p speeds:%s%s\n",
             config->bConfigurationValue, config,
             config->highspeed ? " high" : "",
             config->fullspeed
                 ? (gadget_is_dualspeed(cdev->gadget)
                     ? " full"
                     : " full/low")
                 : "");
 
         for (i = ; i < MAX_CONFIG_INTERFACES; i++) {
             struct usb_function    *f = config->interface[i];
 
             if (!f)
                 continue;
             DBG(cdev, "  interface %d = %s/%p\n",
                 i, f->name, f);
         }
     }
 
     /* set_alt(), or next config->bind(), sets up
      * ep->driver_data as needed.
      */
     usb_ep_autoconfig_reset(cdev->gadget);
 
 done:
     if (status)
         DBG(cdev, "added config '%s'/%u --> %d\n", config->label,
                 config->bConfigurationValue, status);
     return status;
 }

23行，把配置插入链表。（bind设备的时候初始化的那个链表）

25行，又初始化一个function链表。（一个配置可以有多个接口）

28行，status = config->bind(config);
　　第三次调用bind

找到config->bind的真身，在f_sourcesink.c中

 static int __init sourcesink_bind_config(struct usb_configuration *c)
 {
     struct f_sourcesink    *ss;
     int            status;
 
     ss = kzalloc(sizeof *ss, GFP_KERNEL);
     if (!ss)
         return -ENOMEM;
     init_completion(&ss->gdt_completion);
     ss->function.name = "source/sink";
     ss->function.descriptors = fs_source_sink_descs;
     ss->function.bind = sourcesink_bind;
     ss->function.unbind = sourcesink_unbind;
     ss->function.set_alt = sourcesink_set_alt;
     ss->function.disable = sourcesink_disable;
 
     status = usb_add_function(c, &ss->function);
     if (status)
         kfree(ss);
     return status;
 }

留意一下12行function.bind

17行status = usb_add_function(c, &ss->function);

函数在composite.c中

 int usb_add_function(struct usb_configuration *config,
         struct usb_function *function)
 {
     int    value = -EINVAL;
 
     DBG(config->cdev, "adding '%s'/%p to config '%s'/%p\n",
             function->name, function,
             config->label, config);
 
     if (!function->set_alt || !function->disable)
         goto done;
 
     function->config = config;
     list_add_tail(&function->list, &config->functions);
 
     /* REVISIT *require* function->bind? */
     if (function->bind) {
         value = function->bind(config, function);
         if (value < ) {
             list_del(&function->list);
             function->config = NULL;
         }
     } else
         value = ;
 
     /* We allow configurations that don't work at both speeds.
      * If we run into a lowspeed Linux system, treat it the same
      * as full speed ... it's the function drivers that will need
      * to avoid bulk and ISO transfers.
      */
     if (!config->fullspeed && function->descriptors)
         config->fullspeed = true;
     if (!config->highspeed && function->hs_descriptors)
         config->highspeed = true;
 
 done:
     if (value)
         DBG(config->cdev, "adding '%s'/%p --> %d\n",
                 function->name, function, value);
     return value;
 }

14行，同样把function插入链表

18行，第四次调用bind

回顾一下第一次bind设备，第二次bind配置，第三次bind接口，第四次该端点了

直接到f_sourcesink.c中：

 static int __init
 sourcesink_bind(struct usb_configuration *c, struct usb_function *f)
 {
     struct usb_composite_dev *cdev = c->cdev;
     struct f_sourcesink    *ss = func_to_ss(f);
     int    id;
 
     /* allocate interface ID(s) */
     id = usb_interface_id(c, f);
     if (id < )
         return id;
     source_sink_intf.bInterfaceNumber = id;
 
     /* allocate endpoints */
     ss->in_ep = usb_ep_autoconfig(cdev->gadget, &fs_source_desc);
     if (!ss->in_ep) {
 autoconf_fail:
         ERROR(cdev, "%s: can't autoconfigure on %s\n",
             f->name, cdev->gadget->name);
         return -ENODEV;
     }
     ss->in_ep->driver_data = cdev;    /* claim */
 
     ss->out_ep = usb_ep_autoconfig(cdev->gadget, &fs_sink_desc);
     if (!ss->out_ep)
         goto autoconf_fail;
     ss->out_ep->driver_data = cdev;    /* claim */
 
     /* support high speed hardware */
     if (gadget_is_dualspeed(c->cdev->gadget)) {
         hs_source_desc.bEndpointAddress =
                 fs_source_desc.bEndpointAddress;
         hs_sink_desc.bEndpointAddress =
                 fs_sink_desc.bEndpointAddress;
         f->hs_descriptors = hs_source_sink_descs;
     }
 
     DBG(cdev, "%s speed %s: IN/%s, OUT/%s\n",
             gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
             f->name, ss->in_ep->name, ss->out_ep->name);
     return ;
 }

15 和24 行分别获得了一个端口。 gadget zero设备使用了两个端口来收发数据。

以上差不多就是gadget驱动的注册和bind的过程。