Driver (struct usb_driver)
31 Jan 2024
Read time: 6 minute(s)
USB Interface 这一层次的驱动就非常的多了，这一层主要是在 USB 传输层之上，针对 USB Device 的某个功能
Function 开发对应的 USB 功能业务驱动，即常说的 USB Client
Software。在 USB 定义中，一个 Interface 就是一个
Function。
USB Interface Driver 对应的数据结构为 struct usb_driver ，使用
usb_register_driver()
函数进行注册：int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
const char *mod_name)
{
/* (1) 设置 devices 标志为 0，表面这个驱动时给 usb interface 使用的 */
new_driver->drvwrap.for_devices = 0;
new_driver->drvwrap.driver.name = new_driver->name;
new_driver->drvwrap.driver.bus = &usb_bus_type;
new_driver->drvwrap.driver.probe = usb_probe_interface;
new_driver->drvwrap.driver.remove = usb_unbind_interface;
new_driver->drvwrap.driver.owner = owner;
new_driver->drvwrap.driver.mod_name = mod_name;
new_driver->drvwrap.driver.dev_groups = new_driver->dev_groups;
spin_lock_init(&new_driver->dynids.lock);
INIT_LIST_HEAD(&new_driver->dynids.list);
retval = driver_register(&new_driver->drvwrap.driver);
}
一个最简单的
Usb Interface Driver 是 usb_mouse_driver
:static const struct usb_device_id usb_mouse_id_table[] = {
{ USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
USB_INTERFACE_PROTOCOL_MOUSE) },
{ } /* Terminating entry */
};
MODULE_DEVICE_TABLE (usb, usb_mouse_id_table);
static struct usb_driver usb_mouse_driver = {
.name = "usbmouse",
.probe = usb_mouse_probe,
.disconnect = usb_mouse_disconnect,
.id_table = usb_mouse_id_table,
};
module_usb_driver(usb_mouse_driver);-
首先根据得到的 endpoint 准备好 urb，创建好 input 设备：
static int usb_mouse_probe(struct usb_interface *intf, const struct usb_device_id *id) { struct usb_device *dev = interface_to_usbdev(intf); struct usb_host_interface *interface; struct usb_endpoint_descriptor *endpoint; struct usb_mouse *mouse; struct input_dev *input_dev; int pipe, maxp; int error = -ENOMEM; interface = intf->cur_altsetting; if (interface->desc.bNumEndpoints != 1) return -ENODEV; /* (1) 得到当前 interface 中的第一个 endpoint，mouse 设备只需一个 endpoint */ endpoint = &interface->endpoint[0].desc; if (!usb_endpoint_is_int_in(endpoint)) return -ENODEV; pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress); maxp = usb_maxpacket(dev, pipe, usb_pipeout(pipe)); mouse = kzalloc(sizeof(struct usb_mouse), GFP_KERNEL); /* (2.1) 分配 input device */ input_dev = input_allocate_device(); if (!mouse || !input_dev) goto fail1; mouse->data = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &mouse->data_dma); if (!mouse->data) goto fail1; /* (3.1) 分配 urb */ mouse->irq = usb_alloc_urb(0, GFP_KERNEL); if (!mouse->irq) goto fail2; mouse->usbdev = dev; mouse->dev = input_dev; if (dev->manufacturer) strlcpy(mouse->name, dev->manufacturer, sizeof(mouse->name)); if (dev->product) { if (dev->manufacturer) strlcat(mouse->name, " ", sizeof(mouse->name)); strlcat(mouse->name, dev->product, sizeof(mouse->name)); } if (!strlen(mouse->name)) snprintf(mouse->name, sizeof(mouse->name), "USB HIDBP Mouse %04x:%04x", le16_to_cpu(dev->descriptor.idVendor), le16_to_cpu(dev->descriptor.idProduct)); usb_make_path(dev, mouse->phys, sizeof(mouse->phys)); strlcat(mouse->phys, "/input0", sizeof(mouse->phys)); /* (2.2) 初始化 input device */ input_dev->name = mouse->name; input_dev->phys = mouse->phys; usb_to_input_id(dev, &input_dev->id); input_dev->dev.parent = &intf->dev; input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL); input_dev->keybit[BIT_WORD(BTN_MOUSE)] = BIT_MASK(BTN_LEFT) | BIT_MASK(BTN_RIGHT) | BIT_MASK(BTN_MIDDLE); input_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y); input_dev->keybit[BIT_WORD(BTN_MOUSE)] |= BIT_MASK(BTN_SIDE) | BIT_MASK(BTN_EXTRA); input_dev->relbit[0] |= BIT_MASK(REL_WHEEL); input_set_drvdata(input_dev, mouse); input_dev->open = usb_mouse_open; input_dev->close = usb_mouse_close; /* (3.2) 初始化 urb */ usb_fill_int_urb(mouse->irq, dev, pipe, mouse->data, (maxp > 8 ? 8 : maxp), usb_mouse_irq, mouse, endpoint->bInterval); mouse->irq->transfer_dma = mouse->data_dma; mouse->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP; /* (2.3) 注册 input device */ error = input_register_device(mouse->dev); if (error) goto fail3; usb_set_intfdata(intf, mouse); return 0; fail3: usb_free_urb(mouse->irq); fail2: usb_free_coherent(dev, 8, mouse->data, mouse->data_dma); fail1: input_free_device(input_dev); kfree(mouse); return error; } -
在 input device 被 open 时提交 urb 启动传输：
static int usb_mouse_open(struct input_dev *dev) { struct usb_mouse *mouse = input_get_drvdata(dev); mouse->irq->dev = mouse->usbdev; /* (1) 提交初始化好的 usb，开始查询数据 */ if (usb_submit_urb(mouse->irq, GFP_KERNEL)) return -EIO; return 0; } -
在传输完 urb 的回调函数中，根据读回的数据上报 input 事件，并且重新提交 urb 继续查询：
static void usb_mouse_irq(struct urb *urb) { struct usb_mouse *mouse = urb->context; signed char *data = mouse->data; struct input_dev *dev = mouse->dev; int status; switch (urb->status) { case 0: /* success */ break; case -ECONNRESET: /* unlink */ case -ENOENT: case -ESHUTDOWN: return; /* -EPIPE: should clear the halt */ default: /* error */ goto resubmit; } /* (1) 根据 urb 读回的数据，上报 input event */ input_report_key(dev, BTN_LEFT, data[0] & 0x01); input_report_key(dev, BTN_RIGHT, data[0] & 0x02); input_report_key(dev, BTN_MIDDLE, data[0] & 0x04); input_report_key(dev, BTN_SIDE, data[0] & 0x08); input_report_key(dev, BTN_EXTRA, data[0] & 0x10); input_report_rel(dev, REL_X, data[1]); input_report_rel(dev, REL_Y, data[2]); input_report_rel(dev, REL_WHEEL, data[3]); input_sync(dev); resubmit: /* (2) 重新提交 urb 继续查询 */ status = usb_submit_urb (urb, GFP_ATOMIC); if (status) dev_err(&mouse->usbdev->dev, "can't resubmit intr, %s-%s/input0, status %d\n", mouse->usbdev->bus->bus_name, mouse->usbdev->devpath, status); }