gadget之composite

川长思鸟来 2022-10-23 00:52 198阅读 0赞

# gadget之composite #

## composite简介 ##

composite英文意思为复合/综合。其为整个gadget驱动的中间层，往下注册usb\_gadget\_driver并与usb\_udc（usb\_gadget设备）绑定，往上通过usb\_composite\_dev与usb\_composite\_driver实现usb\_function的绑定。usb\_function、composite、udc三者相互联系共同实现usb device的功能。

## struct usb\_composite\_dev ##

//作为composite复合设备，所有composite设备都必须实现该结构体。
    struct usb_composite_dev {
    	struct usb_gadget		*gadget; //设备和gadget交互，gadget与udc交互
    	struct usb_request		*req; //used for control responses; buffer is pre-allocated
    	struct usb_request		*os_desc_req; //used for OS descriptors responses; buffer is pre-allocated
    
    	struct usb_configuration	*config; //当前激活的配置
    
    	/* OS String is a custom (yet popular) extension to the USB standard. */
    	u8				qw_sign[OS_STRING_QW_SIGN_LEN]; //qwSignature part of the OS string
    	u8				b_vendor_code; //bMS_VendorCode part of the OS string
    	struct usb_configuration	*os_desc_config; //the configuration to be used with OS descriptors
    	unsigned int			use_os_string:1; //false by default, interested gadgets set it
    
    	/* private: */
    	/* internals */
    	unsigned int			suspended:1;
    	struct usb_device_descriptor	desc; //设备描述符，唯一
    	struct list_head		configs; //配置链表
    	struct list_head		gstrings; //字符描述链表
    	struct usb_composite_driver	*driver; //设备绑定的composite驱动
    	u8				next_string_id;
    	char				*def_manufacturer; //默认制造商
    
    	/* the gadget driver won't enable the data pullup
    	 * while the deactivation count is nonzero.
    	 */
    	unsigned			deactivations;
    
    	/* the composite driver won't complete the control transfer's
    	 * data/status stages till delayed_status is zero.
    	 */
    	int				delayed_status;
    
    	/* protects deactivations and delayed_status counts*/
    	spinlock_t			lock;
    
    	/* public: */
    	unsigned int			setup_pending:1;
    	unsigned int			os_desc_pending:1;
    };

USB\_COMPOSITE\_DEV的创建

源码：/drivers/usb/gadget/composite.c

static int composite_bind(struct usb_gadget *gadget,
    		struct usb_gadget_driver *gdriver)
    {
    	struct usb_composite_dev	*cdev;
    	struct usb_composite_driver	*composite = to_cdriver(gdriver);
    	int				status = -ENOMEM;
    
    	cdev = kzalloc(sizeof *cdev, GFP_KERNEL);//创建usb_composite_dev
    	if (!cdev)
    		return status;
    
    	spin_lock_init(&cdev->lock);
    	cdev->gadget = gadget;
    	set_gadget_data(gadget, cdev);
    	INIT_LIST_HEAD(&cdev->configs);
    	INIT_LIST_HEAD(&cdev->gstrings);
    
        //初始化conctrl req
    	status = composite_dev_prepare(composite, cdev);
    	if (status)
    		goto fail;
    
    	/* composite gadget needs to assign strings for whole device (like
    	 * serial number), register function drivers, potentially update
    	 * power state and consumption, etc
    	 */
    	 //初始化设备描述符、字符描述付等
    	status = composite->bind(cdev);
    	if (status < 0)
    		goto fail;
    
    	if (cdev->use_os_string) {
    		status = composite_os_desc_req_prepare(cdev, gadget->ep0);
    		if (status)
    			goto fail;
    	}
    
    	update_unchanged_dev_desc(&cdev->desc, composite->dev);
    
    	/* has userspace failed to provide a serial number? */
    	if (composite->needs_serial && !cdev->desc.iSerialNumber)
    		WARNING(cdev, "userspace failed to provide iSerialNumber\n");
    
    	INFO(cdev, "%s ready\n", composite->name);
    	return 0;
    
    fail:
    	__composite_unbind(gadget, false);
    	return status;
    }

int composite_dev_prepare(struct usb_composite_driver *composite,
    		struct usb_composite_dev *cdev)
    {
    	struct usb_gadget *gadget = cdev->gadget;
    	int ret = -ENOMEM;
    
    	/* preallocate control response and buffer */
    	cdev->req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
    	if (!cdev->req)
    		return -ENOMEM;
    
        //USB_COMP_EP0_BUFSIZ=4096
    	cdev->req->buf = kmalloc(USB_COMP_EP0_BUFSIZ, GFP_KERNEL);
    	if (!cdev->req->buf)
    		goto fail;
    
        //创建设备文件
    	ret = device_create_file(&gadget->dev, &dev_attr_suspended);
    	if (ret)
    		goto fail_dev;
    
    	cdev->req->complete = composite_setup_complete;
    	cdev->req->context = cdev;
    	gadget->ep0->driver_data = cdev;
    
    	cdev->driver = composite;
    
    	/*
    	 * As per USB compliance update, a device that is actively drawing
    	 * more than 100mA from USB must report itself as bus-powered in
    	 * the GetStatus(DEVICE) call.
    	 */
    	if (CONFIG_USB_GADGET_VBUS_DRAW <= USB_SELF_POWER_VBUS_MAX_DRAW)
    		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(gadget);
    	return 0;
    fail_dev:
    	kfree(cdev->req->buf);
    fail:
    	usb_ep_free_request(gadget->ep0, cdev->req);
    	cdev->req = NULL;
    	return ret;
    }

## struct usb\_composite\_driver ##

struct usb_composite_driver {//所有compesite驱动必须填充该结构体
    	const char				*name;
    	const struct usb_device_descriptor	*dev; //必须实现
    	struct usb_gadget_strings		**strings;
    	enum usb_device_speed			max_speed;
    	unsigned		needs_serial:1;
    
    	int			(*bind)(struct usb_composite_dev *cdev);//必须实现
    	int			(*unbind)(struct usb_composite_dev *); //必须实现
    
    	void			(*disconnect)(struct usb_composite_dev *);
    
    	/* global suspend hooks */
    	void			(*suspend)(struct usb_composite_dev *);
    	void			(*resume)(struct usb_composite_dev *);
    	struct usb_gadget_driver		gadget_driver;这个地方的驱动由composite提供，所有和composite相关的驱动都会默认分配该驱动。
    };

usb\_composite\_driver的创建，以serial.c为例：

源码：/drivers/usb/gadget/legacy/serial.c

static struct usb_composite_driver gserial_driver = {
    	.name		= "g_serial",
    	.dev		= &device_desc,
    	.strings	= dev_strings,
    	.max_speed	= USB_SPEED_SUPER,
    	.bind		= gs_bind,
    	.unbind		= gs_unbind,
    };