linux驱动由浅入深系列:usb子系统之四(android平台鼠标驱动代码分析)

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android上的usb口是支持OTG(on the go)的,USB OTG既可以作为Host又可以作为Device,我们本文来看一下android手机作为Host连接鼠标的情况。
OTG是如何做到既可以做Host又可以作为Device的呢
标准usb接头中有四根线:vbus,gnd,dp(d+),dm(d-),android手机上的usb为miniUSB接口增加了一根id线,用来区分Host、Device。
usb是如何检测设备插入的呢
设备插拔检测都是由hub来进行的,即使不外接hub在USB host controler中也集成了一个roothub。hub上的dp、dm线都有一个15k的下拉电阻拉到低电平,设备端的dp或dm线上有1.5k的上拉电阻,设备插入时就会改变dp、dm线上的电平。
当把一个USB设备插入到一个usb hub的某个端口时,集中器就会检测到设备的接入,从而在下一次受到主机通过中断交互查询时就会向其报告。集中器的端口在没有设备接入时都处于关闭状态,插入设备之后也不会自动打开,必须由主机通过控制交互发出命令予以打开。所以,在得到集中器的报告之后,主机的USB驱动程序就会为新插入的设备调度若干个控制交互,并向集中器发出打开这个端口的命令,这样新插入的设备就会出现在USB总线上了,并为该设备分配唯一的地址。
鼠标插入android手机后代码执行过程分析
1,usb鼠标属于hid设备,linux启动过程中会注册hid总线bus_register(&hid_bus_type)
drivers/hid/hid-core.cstatic int __init hid_init(void){int ret;ret = bus_register(&hid_bus_type);ret = hidraw_init();return 0;}
2,usb鼠标插入后的会调用到hub_port_connect()
drivers\usb\core\hub.cstatic void hub_port_connect(struct usb_hub *hub, int port1, u16 portstatus,u16 portchange){int status, i;unsigned unit_load;struct usb_device *hdev = hub->hdev;struct usb_hcd *hcd = bus_to_hcd(hdev->bus);struct usb_port *port_dev = hub->ports[port1 - 1];struct usb_device *udev = port_dev->child;static int unreliable_port = -1;printk("radia hub_port_connect\n");//////////////////添加logstatus = 0;for (i = 0; i < SET_CONFIG_TRIES; i++) {/* reallocate for each attempt, since references * to the previous one can escape in various ways */udev = usb_alloc_dev(hdev, hdev->bus, port1);////////////////创建一个usb_device设备if (!udev) {dev_err(&port_dev->dev,"couldn't allocate usb_device\n");goto done;}......../* Run it through the hoops (find a driver, etc) */if (!status) {status = usb_new_device(udev);////////////////////////调用usb_new_device-->usb_enumerate_device枚举设备if (status) {mutex_lock(&usb_port_peer_mutex);spin_lock_irq(&device_state_lock);port_dev->child = NULL;spin_unlock_irq(&device_state_lock);mutex_unlock(&usb_port_peer_mutex);} else {if (hcd->usb_phy && !hdev->parent)usb_phy_notify_connect(hcd->usb_phy,udev->speed);}}}
其中会调用usb_alloc_dev创建一个usb_device设备,然后调用usb_new_device-->usb_enumerate_device-->usb_get_configuration-->usb_parse_configuration-->usb_parse_interface(会分配struct usb_interface_cache)-->usb_parse_endpoint分析设备各描述符,最后usb_new_device会调用device_add 这里把这个usb_device注册到usb总线下。
3,当注册这个usb_device的时候usb总线会调用generic driver驱动的probe函数
drivers\usb\core\generic.cstatic int generic_probe(struct usb_device *udev){int err, c;printk("radia generic_probe\n");//////////////////添加logif (udev->authorized == 0)dev_err(&udev->dev, "Device is not authorized for usage\n");else {c = usb_choose_configuration(udev);//////////////////////////选择合适的configurationif (c >= 0) {err = usb_set_configuration(udev, c);/////////////////////////配置合适的configurationif (err && err != -ENODEV) {dev_err(&udev->dev, "can't set config #%d, error %d\n",c, err);/* This need not be fatal.  The user can try to * set other configurations. */}}}/* USB device state == configured ... usable */usb_notify_add_device(udev);return 0;}
这个函数主要为这个usb_device选择一个合适的配置configuration,并且设置这个configuration

4,usb_set_configuration这个函数为这个配置的每个接口初始化为usb_if_device_type类型的设备。

usb_interface设备是挂载usb_device下面的,并且这个usb_device可能有多个usb_interface功能设备。

drivers\usb\core\message.cint usb_set_configuration(struct usb_device *dev, int configuration){if (dev->authorized == 0 || configuration == -1)configuration = 0;else {for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {if (dev->config[i].desc.bConfigurationValue ==configuration) {cp = &dev->config[i];break;}}}if (cp) {nintf = cp->desc.bNumInterfaces;new_interfaces = kmalloc(nintf * sizeof(*new_interfaces),GFP_NOIO);if (!new_interfaces) {dev_err(&dev->dev, "Out of memory\n");return -ENOMEM;}for (; n < nintf; ++n) {new_interfaces[n] = kzalloc(sizeof(struct usb_interface),GFP_NOIO);if (!new_interfaces[n]) {dev_err(&dev->dev, "Out of memory\n");ret = -ENOMEM;free_interfaces:while (--n >= 0)kfree(new_interfaces[n]);kfree(new_interfaces);return ret;}}i = dev->bus_mA - usb_get_max_power(dev, cp);if (i < 0)dev_warn(&dev->dev, "new config #%d exceeds power ""limit by %dmA\n",configuration, -i);}/* * Initialize the new interface structures and the * hc/hcd/usbcore interface/endpoint state. */for (i = 0; i < nintf; ++i) {struct usb_interface_cache *intfc;struct usb_interface *intf;struct usb_host_interface *alt;cp->interface[i] = intf = new_interfaces[i];intfc = cp->intf_cache[i];intf->altsetting = intfc->altsetting;intf->num_altsetting = intfc->num_altsetting;kref_get(&intfc->ref);alt = usb_altnum_to_altsetting(intf, 0);/* No altsetting 0?  We'll assume the first altsetting. * We could use a GetInterface call, but if a device is * so non-compliant that it doesn't have altsetting 0 * then I wouldn't trust its reply anyway. */if (!alt)alt = &intf->altsetting[0];intf->intf_assoc =find_iad(dev, cp, alt->desc.bInterfaceNumber);intf->cur_altsetting = alt;usb_enable_interface(dev, intf, true);intf->dev.parent = &dev->dev;intf->dev.driver = NULL;intf->dev.bus = &usb_bus_type;intf->dev.type = &usb_if_device_type;intf->dev.groups = usb_interface_groups;intf->dev.dma_mask = dev->dev.dma_mask;INIT_WORK(&intf->reset_ws, __usb_queue_reset_device);intf->minor = -1;device_initialize(&intf->dev);pm_runtime_no_callbacks(&intf->dev);dev_set_name(&intf->dev, "%d-%s:%d.%d",dev->bus->busnum, dev->devpath,configuration, alt->desc.bInterfaceNumber);usb_get_dev(dev);}kfree(new_interfaces);ret = usb_control_msg(dev, usb_sndctrlpipe(dev, 0),      USB_REQ_SET_CONFIGURATION, 0, configuration, 0,      NULL, 0, USB_CTRL_SET_TIMEOUT);  /* Now that all the interfaces are set up, register them * to trigger binding of drivers to interfaces.  probe() * routines may install different altsettings and may * claim() any interfaces not yet bound.  Many class drivers * need that: CDC, audio, video, etc. */for (i = 0; i < nintf; ++i) {struct usb_interface *intf = cp->interface[i];dev_dbg(&dev->dev,"adding %s (config #%d, interface %d)\n",dev_name(&intf->dev), configuration,intf->cur_altsetting->desc.bInterfaceNumber);device_enable_async_suspend(&intf->dev);ret = device_add(&intf->dev);if (ret != 0) {dev_err(&dev->dev, "device_add(%s) --> %d\n",dev_name(&intf->dev), ret);continue;}create_intf_ep_devs(intf);}usb_autosuspend_device(dev);return 0;}

5,最后在注册这些interface时,注册函数会调用usb总线的match函数匹配usb_interface和usb_driver

但是usb_bus_type总线只有match函数,没有probe函数需要调用usb_driver的probe函数usb_probe_interface(drivers/usb/core/driver.c),这个函数会真正的调用具体usb_driver的probe函数。root hub或者hub也都是usb_device设备,usb_device下面包含usb_interface功能(function)

drivers/usb/core/driver.cstatic int usb_probe_interface(struct device *dev){struct usb_driver *driver = to_usb_driver(dev->driver);struct usb_interface *intf = to_usb_interface(dev);struct usb_device *udev = interface_to_usbdev(intf);const struct usb_device_id *id;int error = -ENODEV;int lpm_disable_error;printk("radia usb_probe_interface\n");//////////////////添加log/* Carry out a deferred switch to altsetting 0 */if (intf->needs_altsetting0) {error = usb_set_interface(udev, intf->altsetting[0].desc.bInterfaceNumber, 0);if (error < 0)goto err;intf->needs_altsetting0 = 0;}error = driver->probe(intf, id);//////////////////调用具体设备的probeusb_autosuspend_device(udev);return error;}
6,usb鼠标在android代码中没有使用linux中常用的mousedev.c驱动,而是使用了hid-generic驱动,hid-generic.c的代码很简洁
kernel\drivers\hid\hid-generic.c#include <linux/module.h>#include <linux/slab.h>#include <linux/kernel.h>#include <asm/unaligned.h>#include <asm/byteorder.h>#include <linux/hid.h>static const struct hid_device_id hid_table[] = {{ HID_DEVICE(HID_BUS_ANY, HID_GROUP_GENERIC, HID_ANY_ID, HID_ANY_ID) },{ }};MODULE_DEVICE_TABLE(hid, hid_table);static struct hid_driver hid_generic = {.name = "hid-generic",.id_table = hid_table,};module_hid_driver(hid_generic);MODULE_AUTHOR("Henrik Rydberg");MODULE_DESCRIPTION("HID generic driver");MODULE_LICENSE("GPL");其中module_hid_driver定义在kernel\include\linux\hid.h#define module_hid_driver(__hid_driver) \module_driver(__hid_driver, hid_register_driver, \      hid_unregister_driver)
这个宏实际上是调用 __hid_register_driver()接口注册一个hid_driver,并把它挂接在hid_bus_type总线驱动链表上。
7,当鼠标移动或点击时使用input子系统上报Event的代码在
drivers\hid\hid-input.cstatic void hidinput_configure_usage(struct hid_input *hidinput, struct hid_field *field,     struct hid_usage *usage){struct input_dev *input = hidinput->input;struct hid_device *device = input_get_drvdata(input);int max = 0, code;unsigned long *bit = NULL;field->hidinput = hidinput;switch (usage->hid & HID_USAGE_PAGE) {case HID_UP_UNDEFINED:goto ignore;case HID_UP_KEYBOARD:set_bit(EV_REP, input->evbit);if ((usage->hid & HID_USAGE) < 256) {if (!hid_keyboard[usage->hid & HID_USAGE]) goto ignore;map_key_clear(hid_keyboard[usage->hid & HID_USAGE]);} elsemap_key(KEY_UNKNOWN);break;case HID_UP_BUTTON:code = ((usage->hid - 1) & HID_USAGE);switch (field->application) {case HID_GD_MOUSE:case HID_GD_POINTER:  code += BTN_MOUSE; break;////////////////设置鼠标左键的键值case HID_GD_JOYSTICK:if (code <= 0xf)code += BTN_JOYSTICK;elsecode += BTN_TRIGGER_HAPPY - 0x10;break;case HID_GD_GAMEPAD:if (code <= 0xf)code += BTN_GAMEPAD;elsecode += BTN_TRIGGER_HAPPY - 0x10;break;default:switch (field->physical) {case HID_GD_MOUSE:case HID_GD_POINTER:  code += BTN_MOUSE; break;case HID_GD_JOYSTICK: code += BTN_JOYSTICK; break;case HID_GD_GAMEPAD:  code += BTN_GAMEPAD; break;default:              code += BTN_MISC;}}map_key(code);break;............case HID_UP_PID:switch (usage->hid & HID_USAGE) {case 0xa4: map_key_clear(BTN_DEAD);break;default: goto ignore;}break;default:unknown:if (field->report_size == 1) {if (field->report->type == HID_OUTPUT_REPORT) {map_led(LED_MISC);break;}map_key(BTN_MISC);break;}if (field->flags & HID_MAIN_ITEM_RELATIVE) {map_rel(REL_MISC);break;}map_abs(ABS_MISC);break;}if (usage->type == EV_ABS) {int a = field->logical_minimum;int b = field->logical_maximum;if ((device->quirks & HID_QUIRK_BADPAD) && (usage->code == ABS_X || usage->code == ABS_Y)) {a = field->logical_minimum = 0;b = field->logical_maximum = 255;}if (field->application == HID_GD_GAMEPAD || field->application == HID_GD_JOYSTICK)input_set_abs_params(input, usage->code, a, b, (b - a) >> 8, (b - a) >> 4);/////////////////上报键值elseinput_set_abs_params(input, usage->code, a, b, 0, 0);input_abs_set_res(input, usage->code,  hidinput_calc_abs_res(field, usage->code));/* use a larger default input buffer for MT devices */if (usage->code == ABS_MT_POSITION_X && input->hint_events_per_packet == 0)input_set_events_per_packet(input, 60);}return;}
8,usb鼠标插入android手机后的log如下
[   86.501420] msm_otg 78db000.usb: phy_reset: success
[   86.626156] msm_otg 78db000.usb: USB exited from low power mode
[   86.670053] msm_otg 78db000.usb: phy_reset: success
[   86.776425] msm_hsusb_host msm_hsusb_host: EHCI Host Controller
[   86.787250] msm_hsusb_host msm_hsusb_host: new USB bus registered, assigned bus number 1
[   86.803480] msm_hsusb_host msm_hsusb_host: irq 49, io mem 0x078db000
[   86.824675] msm_hsusb_host msm_hsusb_host: USB 2.0 started, EHCI 1.00
[   86.831268] radia usb_new_device
[   86.836682] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
[   86.842444] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[   86.850085] usb usb1: Product: EHCI Host Controller
[   86.854990] usb usb1: Manufacturer: Linux 3.18.31-g6649b1f-dirty ehci_hcd
[   86.861286] usb usb1: SerialNumber: msm_hsusb_host
[   86.876553] radia generic_probe
[   86.882021] hub 1-0:1.0: USB hub found
[   86.885627] hub 1-0:1.0: 1 port detected
[   87.085676] radia hub_port_connect
[   87.204811] usb 1-1: new low-speed USB device number 2 using msm_hsusb_host
[   87.358301] radia usb_new_device
[   87.372341] usb 1-1: New USB device found, idVendor=10c4, idProduct=8108
[   87.378352] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[   87.385665] usb 1-1: Product: USB OPTICAL MOUSE
[   87.389643] usb 1-1: Manufacturer: YSPRINGTECH
[   87.402281] radia generic_probe
[   87.432953] input: YSPRINGTECH USB OPTICAL MOUSE as /devices/soc/78db000.usb/msm_hsusb_host/usb1/1-1/1-1:1.0/0003:10C4:8108.0001/input/input9
[   87.461748] hid-generic 0003:10C4:8108.0001: input,hidraw0: USB HID v1.11 Mouse [YSPRINGTECH USB OPTICAL MOUSE] on usb-msm_hsusb_host-1/input0
[   87.815343] SELinux: initialized (dev fuse, type fuse), uses mountpoint labeling
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