《Linux总线、设备与驱动》USB设备发现机制
说明:本分析基于mstar801平台Linux2.6.35.11内核,其他内核版本仅供参考。
一、程序在内核中的位置
1.usb host做为pci总线下的一个设备存在(嵌入式系统中有可能也会直接挂在CPU上);这部分驱动由厂家实现,本分析以mstar为例。
2.USB总线驱动
kernel/drivers/usb/core/driver.c
- EXPORT_SYMBOL_GPL(usb_register_driver);
- EXPORT_SYMBOL_GPL(usb_deregister);
- EXPORT_SYMBOL_GPL(usb_register_device_driver);
- EXPORT_SYMBOL_GPL(usb_deregister_device_driver);
- struct bus_type usb_bus_type = {
- .name = "usb",
- .match = usb_device_match,
- .uevent = usb_uevent,
- };
kernel/drivers/usb/core/usb.c
- static int __init usb_init(void){
- bus_register(&usb_bus_type);
- usb_register_device_driver(&usb_generic_driver, THIS_MODULE);
- }
3.uvc camera设备驱动
kernel/drivers/media/video/uvc/uvc_driver.c
- usb_register(&uvc_driver.driver);
二、所有总线、设备和驱动的注册函数
1.设备注册
kernel/drivers/base/core.c
- int device_register(struct device *dev){
- device_initialize(dev);
- return device_add(dev);
- }
- int device_add(struct device *dev){ //所有的设备注册都需要走这里!!!!!!
- error = bus_add_device(dev);
- kobject_uevent(&dev->kobj, KOBJ_ADD); //上报uevent事件
- bus_probe_device(dev); //添加到总线
- }
2.驱动注册
kernel/drivers/base/driver.c
- int driver_register(struct device_driver *drv){ //所有的驱动注册都要走这里!!!!!!!
- ret = bus_add_driver(drv); //添加到总线
- }
3.总线注册
kernel/drivers/base/bus.c
- int bus_register(struct bus_type *bus);
三、具体分析
情况一:当插入USB设备时USB host会检测到这一事件;然后通过USB core去匹配驱动。
当守护程序第一次运行(特殊USB设备USB hub就是这种情况)或usb port上状态发生变化(其余所有USB设备插入都是这种情况)守护进程被唤醒时,会运行hub_events函数、USB的枚举过程就是由它完成。
1.USB host部分代码
说明:从硬件层面来看,ehci主控器从PCI总线桥接,是PCI驱动程序实例。
kernel/drivers/usb/host/ehci-hcd.c
- module_init(ehci_hcd_init);
- #define PCI_DRIVER ehci_pci_driver //利用pci中断
- #define PLATFORM_DRIVER ehci_hcd_mstar_driver //利用定时器轮询
- static int __init ehci_hcd_init(void){
- #ifdef PLATFORM_DRIVER
- platform_driver_register(&PLATFORM_DRIVER);
- #endif
- #ifdef PCI_DRIVER
- pci_register_driver(&PCI_DRIVER);
- #endif
- }
下边分两种情况:
==============================================
定时器轮询:
kernel/drivers/usb/host/ehci-mstar.c
- static struct platform_driver ehci_hcd_mstar_driver = {
- .probe = ehci_hcd_mstar_drv_probe,
- };
- static int ehci_hcd_mstar_drv_probe(struct platform_device *pdev){
- usb_ehci_mstar_probe(&ehci_mstar_hc_driver, &hcd, pdev);
- }
- int usb_ehci_mstar_probe(const struct hc_driver *driver,struct usb_hcd **hcd_out, struct platform_device *dev){
- usb_create_hcd(driver, &dev->dev, "mstar");
- }
kernel/drivers/usb/core/hcd.c
- struct usb_hcd *usb_create_hcd(const struct hc_driver *driver, struct device *dev, const char *bus_name){
- return usb_create_shared_hcd(driver, dev, bus_name, NULL);
- }
- struct usb_hcd *usb_create_shared_hcd(const struct hc_driver *driver, struct device *dev, const char *bus_name, struct usb_hcd *primary_hcd){
- init_timer(&hcd->rh_timer);
- hcd->rh_timer.function = rh_timer_func;
- }
- static void rh_timer_func (unsigned long _hcd) {
- usb_hcd_poll_rh_status((struct usb_hcd *) _hcd);
- }
- void usb_hcd_poll_rh_status(struct usb_hcd *hcd){
- hcd->driver->hub_status_data(hcd, buffer);
- usb_hcd_giveback_urb(hcd, urb, 0);
- }
===================
当有pci中断发生后:
kernel/drivers/usb/host/ehci-pci.c
- static struct pci_driver ehci_pci_driver = {
- .id_table = pci_ids,
- }
- static const struct pci_device_id pci_ids [] = { {
- .driver_data = (unsigned long) &ehci_pci_hc_driver,
- }
- }
- static const struct hc_driver ehci_pci_hc_driver = {
- .irq = ehci_irq, //中断
- .hub_status_data = ehci_hub_status_data,
- .urb_enqueue = ehci_urb_enqueue,
- .urb_dequeue = ehci_urb_dequeue,
- }
kernel/drivers/usb/host/ehci-hcd.c
- static irqreturn_t ehci_irq (struct usb_hcd *hcd){
- usb_hcd_poll_rh_status(hcd);
- }
kernel/drivers/usb/core/hcd.c
- void usb_hcd_poll_rh_status(struct usb_hcd *hcd){
- hcd->driver->hub_status_data(hcd, buffer);
- usb_hcd_giveback_urb(hcd, urb, 0);
- }
kernel/drivers/usb/host/ehci-hub.c
- static int ehci_hub_status_data (struct usb_hcd *hcd, char *buf){
- }
=====================================================================
从以上分析可以看出;不论是定时器轮询还是pci中断,最终都会执行usb_hcd_giveback_urb函数:
kernel/drivers/usb/core/hcd.c
- void usb_hcd_giveback_urb(struct usb_hcd *hcd, struct urb *urb, int status){
- urb->complete (urb);
- }
而上处urv->complete函数其实就是如下的hub_irq函数,后边会分析:
kernel/drivers/usb/core/hub.c
- static void hub_irq(struct urb *urb){
- kick_khubd(hub);
- }
2.USB core即USB总线部分代码——可以看到hub是第一个USB设备而且与USB总线密切相关
kernel/drivers/usb/core/usb.c
- subsys_initcall(usb_init);
- struct bus_type usb_bus_type = {
- .name = "usb",
- .match = usb_device_match,
- .uevent = usb_uevent,
- };
- static int __init usb_init(void){
- bus_register(&usb_bus_type);
- usb_register_device_driver(&usb_generic_driver, THIS_MODULE); //USB设备驱动,在没有root hub时使用
- usb_hub_init();
- }
kernel/drivers/usb/core/hub.c
- static struct usb_driver hub_driver = {
- .name = "hub",
- .probe = hub_probe,
- };
- int usb_hub_init(void){
- usb_register(&hub_driver); //USB设备驱动,第一个USB设备—root hub
- kthread_run(hub_thread, NULL, "khubd");
- }
=====================================
插句话:下边就是之前我们说的urv->complete被赋为hub_irq函数的过程;
这里说明一下:hub的探测函数的执行是在守护线程第一次运行时的情况;为什么不需要USB总线轮询后或PCI总线中断后就执行?我们会在后边hub创建线程处看到。
- static int hub_probe(struct usb_interface *intf, const struct usb_device_id *id){
- hub_configure(hub, endpoint);
- }
- static int hub_configure(struct usb_hub *hub,struct usb_endpoint_descriptor *endpoint){
- usb_fill_int_urb(hub->urb, hdev, pipe, *hub->buffer, maxp, hub_irq, hub, endpoint->bInterval);
- }
kernel/include/linux/usb.h
- static inline void usb_fill_int_urb(struct urb *urb, struct usb_device *dev, unsigned int pipe, void *transfer_buffer, int buffer_length,
- usb_complete_t complete_fn, void *context, int interval){
- urb->complete = complete_fn;
- }
=============================================
kernel/drivers/usb/core/hub.c
这里特别强调:hub设备是第一个USB设备,也是必须的USB设备;它不需要通过USB总线定时器轮询或PCI总线中断来触发。从下边代码也可以看出,在执行第一次hub_events之后(hub驱动的probe函数被执行、urv->complete被赋值hub_irq),该线程才会睡眠!
- static int hub_thread(void *__unused){
- do {
- hub_events(); //重要!最核心部分
- wait_event_freezable(khubd_wait,!list_empty(&hub_event_list) || kthread_should_stop());
- } while (!kthread_should_stop() || !list_empty(&hub_event_list));
- }
- //内核守护线程khubd,它被kick_khubd唤醒(当prot上状态发生变化时,USB host会调用usb_hcd_poll_rh_status去查询usb root hub port状态,并调用hub中的interrupt urb的回调函数hub_irq,最终去唤醒usb内核守护线程)、通过自身调用wait_event_freezable进入睡眠。
- static void hub_events(void){
- if (connect_change) hub_port_connect_change(hub, i, portstatus, portchange);
- }
- static void hub_port_connect_change(struct usb_hub *hub, int port1, u16 portstatus, u16 portchange){
- status = hub_port_init(hub, udev, port1, i);
- status = usb_new_device(udev);
- }
- int usb_new_device(struct usb_device *udev){
- err = device_add(&udev->dev);
- (void) usb_create_ep_devs(&udev->dev, &udev->ep0, udev);
- /*
- kernel/drivers/usb/core/endpoint.c
- int usb_create_ep_devs(struct device *parent,struct usb_host_endpoint *endpoint,struct usb_device *udev){
- device_register(&ep_dev->dev);
- }
- */
- }
kernel/drivers/base/core.c
- int device_add(struct device *dev){ //所有的设备注册都需要走这里!!!!!!
- error = bus_add_device(dev);
- kobject_uevent(&dev->kobj, KOBJ_ADD); //上报uevent事件
- bus_probe_device(dev);
- }
kernel/drivers/base/bus.c
- void bus_probe_device(struct device *dev){
- ret = device_attach(dev);
- }
kernel/drivers/base/dd.c
- int device_attach(struct device *dev){
- ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
- }
kernel/drivers/base/bus.c
- int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,void *data, int (*fn)(struct device_driver *, void *)){
- while ((drv = next_driver(&i)) && !error)
- error = fn(drv, data);
- }
kernel/drivers/base/dd.c
- static int __device_attach(struct device_driver *drv, void *data){
- if (!driver_match_device(drv, dev))
- return 0;
- /*
- kernel/drivers/base/base.h
- static inline int driver_match_device(struct device_driver *drv,struct device *dev){
- return drv->bus->match ? drv->bus->match(dev, drv) : 1;
- }
- kernel/drivers/usb/core/driver.c
- static int usb_device_match(struct device *dev, struct device_driver *drv){
- intf = to_usb_interface(dev);
- usb_drv = to_usb_driver(drv);
- if (id) return 1;
- id = usb_match_dynamic_id(intf, usb_drv);
- if (id) return 1;
- return 0;
- }
- */
- return driver_probe_device(drv, dev);
- }
- int driver_probe_device(struct device_driver *drv, struct device *dev){
- ret = really_probe(dev, drv);
- }
- static int really_probe(struct device *dev, struct device_driver *drv){
- dev->driver = drv;
- if (dev->bus->probe) {
- ret = dev->bus->probe(dev);
- if (ret) goto probe_failed;
- } else if (drv->probe) {
- ret = drv->probe(dev);
- if (ret) goto probe_failed;
- }
- }
情况二:当加入USB设备驱动时,也会通过USB core调用mattch函数去匹配设备。
kernel/drivers/media/video/uvc/uvc_driver.c
- struct uvc_driver uvc_driver = {
- .driver = {
- .name = "uvcvideo",
- .probe = uvc_probe,
- .disconnect = uvc_disconnect,
- .suspend = uvc_suspend,
- .resume = uvc_resume,
- .reset_resume = uvc_reset_resume,
- .id_table = uvc_ids,
- .supports_autosuspend = 1,
- },
- };
- module_init(uvc_init);
- static int __init uvc_init(void){
- result = usb_register(&uvc_driver.driver);
- }
kernel/include/linux/usb.h
- static inline int usb_register(struct usb_driver *driver){
- return usb_register_driver(driver, THIS_MODULE, KBUILD_MODNAME);
- }
kernel/drivers/usb/core/driver.c
- int usb_register_driver(struct usb_driver *new_driver, struct module *owner, const char *mod_name){
- retval = driver_register(&new_driver->drvwrap.driver);
- }
kernel/drivers/base/driver.c
- int driver_register(struct device_driver *drv){ //所有的驱动注册都要走这里!!!!!!!
- ret = bus_add_driver(drv);
- }
kernel/drivers/base/bus.c
- int bus_add_driver(struct device_driver *drv){
- error = driver_attach(drv);
- kobject_uevent(&priv->kobj, KOBJ_ADD);
- }
kernel/drivers/base/dd.c
- int driver_attach(struct device_driver *drv){
- return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
- }
kernel/drivers/base/bus.c
- int bus_for_each_dev(struct bus_type *bus, struct device *start, void *data, int (*fn)(struct device *, void *)){
- while ((dev = next_device(&i)) && !error) error = fn(dev, data);
- }
kernel/drivers/base/dd.c
- static int __driver_attach(struct device *dev, void *data){
- if (!driver_match_device(drv, dev)) return 0;
- /*
- kernel/drivers/base/base.h
- static inline int driver_match_device(struct device_driver *drv,struct device *dev){
- return drv->bus->match ? drv->bus->match(dev, drv) : 1;
- }
- kernel/drivers/usb/core/driver.c
- static int usb_device_match(struct device *dev, struct device_driver *drv){
- intf = to_usb_interface(dev);
- usb_drv = to_usb_driver(drv);
- if (id) return 1;
- id = usb_match_dynamic_id(intf, usb_drv);
- if (id) return 1;
- return 0;
- }
- */
- if (!dev->driver) driver_probe_device(drv, dev);
- }
- int driver_probe_device(struct device_driver *drv, struct device *dev){
- ret = really_probe(dev, drv);
- }
- static int really_probe(struct device *dev, struct device_driver *drv){
- dev->driver = drv;
- if (dev->bus->probe) {
- ret = dev->bus->probe(dev);
- if (ret) goto probe_failed;
- } else if (drv->probe) {
- ret = drv->probe(dev);
- if (ret) goto probe_failed;
- }
- }
3.总结
经过分析,总结:
(1).当总线上插入设备、总线会调用设备注册函数device_add/device_register;
(2).当insmod设备驱动、module_init函数里边一定有driver_register;
(3).通过上边分析,如上两个函数最终都会调用到总线驱动的match函数、进行匹配;如USB的总线match函数如下:
kernel/drivers/usb/core/driver.c
- struct bus_type usb_bus_type = {
- .name = "usb",
- .match = usb_device_match,
- .uevent = usb_uevent,
- .pm = &usb_bus_pm_ops,
- };
- static int usb_device_match(struct device *dev, struct device_driver *drv)
- {
- /* devices and interfaces are handled separately */
- if (is_usb_device(dev)) {
- /* interface drivers never match devices */
- if (!is_usb_device_driver(drv))
- return 0;
- /* TODO: Add real matching code */
- return 1;
- } else if (is_usb_interface(dev)) {
- struct usb_interface *intf;
- struct usb_driver *usb_drv;
- const struct usb_device_id *id;
- /* device drivers never match interfaces */
- if (is_usb_device_driver(drv))
- return 0;
- intf = to_usb_interface(dev);
- usb_drv = to_usb_driver(drv);
- id = usb_match_id(intf, usb_drv->id_table);//USB是匹配驱动中的id_table
- if (id)
- return 1;
- id = usb_match_dynamic_id(intf, usb_drv);
- if (id)
- return 1;
- }
- return 0;
- }
下边也看看UVC Camera驱动的id_table:
kernel/drivers/media/video/uvc/uvc_driver.c
- struct uvc_driver uvc_driver = {
- .driver = {
- .name = "uvcvideo",
- .probe = uvc_probe,
- .disconnect = uvc_disconnect,
- .suspend = uvc_suspend,
- .resume = uvc_resume,
- .reset_resume = uvc_reset_resume,
- .id_table = uvc_ids,
- .supports_autosuspend = 1,
- },
- };
- static struct usb_device_id uvc_ids[] = {
- /* Microsoft Lifecam NX-6000 */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x045e,
- .idProduct = 0x00f8,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_PROBE_MINMAX },
- /* Microsoft Lifecam VX-7000 */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x045e,
- .idProduct = 0x0723,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_PROBE_MINMAX },
- /* Logitech Quickcam Fusion */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x046d,
- .idProduct = 0x08c1,
- .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0 },
- /* Logitech Quickcam Orbit MP */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x046d,
- .idProduct = 0x08c2,
- .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0 },
- /* Logitech Quickcam Pro for Notebook */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x046d,
- .idProduct = 0x08c3,
- .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0 },
- /* Logitech Quickcam Pro 5000 */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x046d,
- .idProduct = 0x08c5,
- .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0 },
- /* Logitech Quickcam OEM Dell Notebook */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x046d,
- .idProduct = 0x08c6,
- .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0 },
- /* Logitech Quickcam OEM Cisco VT Camera II */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x046d,
- .idProduct = 0x08c7,
- .bInterfaceClass = USB_CLASS_VENDOR_SPEC,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0 },
- /* Apple Built-In iSight */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x05ac,
- .idProduct = 0x8501,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_PROBE_MINMAX
- | UVC_QUIRK_BUILTIN_ISIGHT },
- /* Genesys Logic USB 2.0 PC Camera */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x05e3,
- .idProduct = 0x0505,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STREAM_NO_FID },
- /* MT6227 */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x0e8d,
- .idProduct = 0x0004,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_PROBE_MINMAX },
- /* Syntek (HP Spartan) */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x174f,
- .idProduct = 0x5212,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STREAM_NO_FID },
- /* Syntek (Samsung Q310) */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x174f,
- .idProduct = 0x5931,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STREAM_NO_FID },
- /* Asus F9SG */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x174f,
- .idProduct = 0x8a31,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STREAM_NO_FID },
- /* Syntek (Asus U3S) */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x174f,
- .idProduct = 0x8a33,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STREAM_NO_FID },
- /* Lenovo Thinkpad SL500 */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x17ef,
- .idProduct = 0x480b,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STREAM_NO_FID },
- /* Ecamm Pico iMage */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x18cd,
- .idProduct = 0xcafe,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_PROBE_EXTRAFIELDS },
- /* Bodelin ProScopeHR */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_DEV_HI
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x19ab,
- .idProduct = 0x1000,
- .bcdDevice_hi = 0x0126,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_STATUS_INTERVAL },
- /* SiGma Micro USB Web Camera */
- { .match_flags = USB_DEVICE_ID_MATCH_DEVICE
- | USB_DEVICE_ID_MATCH_INT_INFO,
- .idVendor = 0x1c4f,
- .idProduct = 0x3000,
- .bInterfaceClass = USB_CLASS_VIDEO,
- .bInterfaceSubClass = 1,
- .bInterfaceProtocol = 0,
- .driver_info = UVC_QUIRK_PROBE_MINMAX
- | UVC_QUIRK_IGNORE_SELECTOR_UNIT
- | UVC_QUIRK_PRUNE_CONTROLS },
- /* Generic USB Video Class */
- { USB_INTERFACE_INFO(USB_CLASS_VIDEO, 1, 0) },
- {}
- };
(4).如果匹配成功,会执行设备驱动的probe函数。我们关心的设备节点的创建也是在设备驱动的探测函数中被创建(因为这时的设备注册会附带主次设备号,内核通过netlink上报uevent事件后、用户空间的udevd服务会执行mknod创建设备节点)详见Linux驱动中uevent、netlink及kobject初探——kobject部分 和 Linux驱动中uevent、netlink及kobject初探——ueventd部分。
三、usb相关结构说明
1.设备描述符
- struct usb_device_descriptor {
- __u8 bLength; --描述符长度
- __u8 bDescriptorType; --描述符类型:设备描述符0x01
- __le16 bcdUSB; --usb规范版本号
- __u8 bDeviceClass; --类代码
- __u8 bDeviceSubClass; --子类代码
- __u8 bDeviceProtocol; --协议代码
- __u8 bMaxPacketSize0; --端点0支持最大数
- __le16 idVendor; --供应商ID
- __le16 idProduct; --产品ID
- __le16 bcdDevice; --设备版本号
- __u8 iManufacturer; --供应商字符串描述符的索引值
- __u8 iProduct; --产品字符串描述符的索引值
- __u8 iSerialNumber; --设备序列号
- __u8 bNumConfigurations; --所支持的配置数
- } __attribute__ ((packed)); --结构体字符类型对齐
2.配置描述符
- struct usb_config_descriptor {
- __u8 bLength; --描述符长度
- __u8 bDescriptorType; --描述符类型
- __le16 wTotalLength; --配置信息的总长度
- __u8 bNumInterfaces; --所支持的接口数
- __u8 bConfigurationValue; --配置值
- __u8 iConfiguration; --字符串描述符的索引值
- __u8 bmAttributes; --配置特征
- __u8 bMaxPower; --所需最大的总线电流
- } __attribute__ ((packed));
3.接口描述符
- struct usb_interface_descriptor {
- __u8 bLength;
- __u8 bDescriptorType;
- __u8 bInterfaceNumber; --接口编号
- __u8 bAlternateSetting; --备用接口标号
- __u8 bNumEndpoints; --接口数目
- __u8 bInterfaceClass; --接口类型
- __u8 bInterfaceSubClass; --接口子类型
- __u8 bInterfaceProtocol; --接口所用协议
- __u8 iInterface; --接口索引字符串数值
- } __attribute__ ((packed));
4.端点描述符
- struct usb_endpoint_descriptor {
- __u8 bLength;
- __u8 bDescriptorType;
- __u8 bEndpointAddress; --端点号包括传输方向
- __u8 bmAttributes; --端点属性
- __le16 wMaxPacketSize; --最大数据包长度
- __u8 bInterval; --访问间隔
- __u8 bRefresh;
- __u8 bSynchAddress;
- } __attribute__ ((packed));
usb总线驱动中对于设备和设备驱动的匹配函数,其实就是上述1和3的匹配过程
见:kernel/drivers/usb/core/driver.c中usb_device_match函数,这部分可以进一步分析;在此、我不再分析。
大致会匹配设备所属类(Input设备?Camera设备?Audio设备?或显示设备等)和VID、PID。
五、urb数据传输分析
未完待续
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