Usb_skeleton.c,是USB驱动的框架,适合USB驱动的初学者。 1.结构体 内核其实就是一坨坨的数据结构,加上一根根链表。 对于初学者,如果直接看USB驱动代码,大概会被那些名字相近的结构体弄得晕头转向,比如usb_host_interface和usb_interface,看着看着就把两个混淆了。所以,在学习USB驱动之前,建议把相关结构体都拎出来看一下,其实,也就那么几个结构体在那装神弄鬼。USB skeleton驱动中用到的主要字段已用蓝色标出: endpoint: struct usb_host_endpoint { struct usb_endpoint_descriptor desc; struct list_head urb_list; void *hcpriv; unsigned char *extra; int extralen; }; struct usb_endpoint_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bEndpointAddress; __u8 bmAttributes; __le16 wMaxPacketSize; __u8 bInterval; __u8 bRefresh; __u8 bSynchAddress; } __attribute__ ((packed)); bEndpointAddress,最高位用来判断传输方向: #define USB_ENDPOINT_NUMBER_MASK 0x0f #define USB_ENDPOINT_DIR_MASK 0x80 #define USB_DIR_OUT 0 #define USB_DIR_IN 0x80 bmAttributes,表示endpoint的类型: #define USB_ENDPOINT_XFERTYPE_MASK 0x03 #define USB_ENDPOINT_XFER_CONTROL 0 #define USB_ENDPOINT_XFER_ISOC 1 #define USB_ENDPOINT_XFER_BULK 2 #define USB_ENDPOINT_XFER_INT 3 bInterval,如果该endpoint是interrupt类型的(USB鼠标驱动就是该类型),那么bInterval就表示中断时间间隔,单位毫秒。 interface: struct usb_interface { struct usb_host_interface *altsetting; struct usb_host_interface *cur_altsetting; unsigned num_altsetting; int minor; enum usb_interface_condition condition; struct device dev; struct class_device *class_dev; }; struct usb_host_interface { struct usb_interface_descriptor desc; struct usb_host_endpoint *endpoint; char *string; unsigned char *extra; int extralen; }; struct usb_interface_descriptor { __u8 bLength; __u8 bDescriptorType; __u8 bInterfaceNumber; __u8 bAlternateSetting; __u8 bNumEndpoints; __u8 bInterfaceClass; __u8 bInterfaceSubClass; __u8 bInterfaceProtocol; __u8 iInterface; } __attribute__ ((packed)); usb_device: struct usb_device { int devnum; char devpath [16]; enum usb_device_state state; enum usb_device_speed speed; struct usb_tt *tt; int ttport; struct semaphore serialize; unsigned int toggle[2]; struct usb_device *parent; struct usb_bus *bus; struct usb_host_endpoint ep0; struct device dev; struct usb_device_descriptor descriptor; struct usb_host_config *config; struct usb_host_config *actconfig; struct usb_host_endpoint *ep_in[16]; struct usb_host_endpoint *ep_out[16]; char **rawdescriptors; int have_langid; int string_langid; char *product; char *manufacturer; char *serial; struct list_head filelist; struct dentry *usbfs_dentry; int maxchild; struct usb_device *children[USB_MAXCHILDREN]; }; usb_driver: struct usb_driver { struct module *owner; const char *name; int (*probe) (struct usb_interface *intf, const struct usb_device_id *id); void (*disconnect) (struct usb_interface *intf); int (*ioctl) (struct usb_interface *intf, unsigned int code, void *buf); int (*suspend) (struct usb_interface *intf, pm_message_t message); int (*resume) (struct usb_interface *intf); const struct usb_device_id *id_table; struct device_driver driver; }; 2.Init 先来看模块初始化函数,它仅仅完成一个功能,那就是注册USB驱动: static int __init usb_skel_init(void) { int result; result = usb_register(&skel_driver); if (result)
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