USB 设备驱动之设备接入梳理（二）

USB提供了一套自顶向下的识别方法，从hub_event出发，检查是否真的有端口发生了改变，如果坐实是port被触发了，则进入port_event。

port_event()

先去获取hub的状态

if (hub_port_status(hub, port1, &portstatus, &portchange) < 0)return;

最终也是调用get_port_stats()函数去获得想要的状态，hub也是一类usb设备，

static int get_port_status(struct usb_device *hdev, int port1,void *data, u16 value, u16 length)
{int i, status = -ETIMEDOUT;for (i = 0; i < USB_STS_RETRIES &&(status == -ETIMEDOUT || status == -EPIPE); i++) {status = usb_control_msg(hdev, usb_rcvctrlpipe(hdev, 0),USB_REQ_GET_STATUS, USB_DIR_IN | USB_RT_PORT, value,port1, data, length, USB_STS_TIMEOUT);}return status;
}

根据spec对于port状态的请求

状态字段的定于

驱动也有相同的宏定义：

/** wPortChange bit field* See USB 2.0 spec Table 11-22 and USB 2.0 LPM ECN Table-4.10* Bits 0 to 5 shown, bits 6 to 15 are reserved*/
#define USB_PORT_STAT_C_CONNECTION  0x0001
#define USB_PORT_STAT_C_ENABLE      0x0002
#define USB_PORT_STAT_C_SUSPEND     0x0004
#define USB_PORT_STAT_C_OVERCURRENT 0x0008
#define USB_PORT_STAT_C_RESET       0x0010
#define USB_PORT_STAT_C_L1          0x0020

/*
122   * wPortStatus bit field
123   * See USB 2.0 spec Table 11-21
124   */
125  #define USB_PORT_STAT_CONNECTION   0x0001
126  #define USB_PORT_STAT_ENABLE       0x0002
127  #define USB_PORT_STAT_SUSPEND      0x0004
128  #define USB_PORT_STAT_OVERCURRENT  0x0008
129  #define USB_PORT_STAT_RESET        0x0010
130  #define USB_PORT_STAT_L1       0x0020
131  /* bits 6 to 7 are reserved */
132  #define USB_PORT_STAT_POWER        0x0100
133  #define USB_PORT_STAT_LOW_SPEED        0x0200
134  #define USB_PORT_STAT_HIGH_SPEED        0x0400
135  #define USB_PORT_STAT_TEST              0x0800
136  #define USB_PORT_STAT_INDICATOR         0x1000

然后引发了一串 if 判断...

 if (portchange & USB_PORT_STAT_C_CONNECTION) {               //有新设备接入？usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_CONNECTION);connect_change = 1;}if (portchange & USB_PORT_STAT_C_ENABLE) {              //hub上port是否使能？if (!connect_change)dev_dbg(&port_dev->dev, "enable change, status %08x\n",portstatus);usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_ENABLE);/** EM interference sometimes causes badly shielded USB devices* to be shutdown by the hub, this hack enables them again.* Works at least with mouse driver.*/if (!(portstatus & USB_PORT_STAT_ENABLE)&& !connect_change && udev) {dev_err(&port_dev->dev, "disabled by hub (EMI?), re-enabling...\n");connect_change = 1;}}if (portchange & USB_PORT_STAT_C_OVERCURRENT) {   //过电流？u16 status = 0, unused;dev_dbg(&port_dev->dev, "over-current change\n");usb_clear_port_feature(hdev, port1,USB_PORT_FEAT_C_OVER_CURRENT);msleep(100);    /* Cool down */hub_power_on(hub, true);hub_port_status(hub, port1, &status, &unused);if (status & USB_PORT_STAT_OVERCURRENT)dev_err(&port_dev->dev, "over-current condition\n");}if (portchange & USB_PORT_STAT_C_RESET) {  //重启？dev_dbg(&port_dev->dev, "reset change\n");usb_clear_port_feature(hdev, port1, USB_PORT_FEAT_C_RESET);}if ((portchange & USB_PORT_STAT_C_BH_RESET)     //以下是usb3.0相关的状态&& hub_is_superspeed(hdev)) {dev_dbg(&port_dev->dev, "warm reset change\n");usb_clear_port_feature(hdev, port1,USB_PORT_FEAT_C_BH_PORT_RESET);}if (portchange & USB_PORT_STAT_C_LINK_STATE) {dev_dbg(&port_dev->dev, "link state change\n");usb_clear_port_feature(hdev, port1,USB_PORT_FEAT_C_PORT_LINK_STATE);}if (portchange & USB_PORT_STAT_C_CONFIG_ERROR) {dev_warn(&port_dev->dev, "config error\n");usb_clear_port_feature(hdev, port1,USB_PORT_FEAT_C_PORT_CONFIG_ERROR);}

connect_change 标志，用来标志着是不是真的有端口改变了。如果真的改变了，需要处理调用hub_port_connect_change()函数。

if (connect_change)hub_port_connect_change(hub, port1, portstatus, portchange);

总结一下，在那些情况下会使得 connect_change 标志位为1？

答：1. 端口对应的hub->change_bits 被置1

2.有设备接入的时候

3. 远程唤醒hub端口

port_event() 函数都干了些啥？

答：判定hub的port发生了什么（设备接入、唤醒...），做出相应的响应。

hub_port_connect_change()

函数原型：

/* Handle physical or logical connection change events.* This routine is called when:*   a port connection-change occurs;*   a port enable-change occurs (often caused by EMI);* usb_reset_and_verify_device() encounters changed descriptors (as from*      a firmware download)* caller already locked the hub*/
static void hub_port_connect_change(struct usb_hub *hub, int port1,u16 portstatus, u16 portchange)__must_hold(&port_dev->status_lock)

功能：响应物理层或者逻辑层的port改变

适用于：端口连接情况发生改变；端口使能情况发生改变等

若hub有指示灯，则开始工作

if (hub->has_indicators) {set_port_led(hub, port1, HUB_LED_AUTO);hub->indicator[port1-1] = INDICATOR_AUTO;}

如支持otg功能，设置标志位

#ifdef   CONFIG_USB_OTG/* during HNP, don't repeat the debounce */if (hub->hdev->bus->is_b_host)portchange &= ~(USB_PORT_STAT_C_CONNECTION |USB_PORT_STAT_C_ENABLE);
#endif

检查端口设备是不是已连接需要被唤醒

 if ((portstatus & USB_PORT_STAT_CONNECTION) && udev &&udev->state != USB_STATE_NOTATTACHED) {if (portstatus & USB_PORT_STAT_ENABLE) {status = 0;       /* Nothing to do */
#ifdef CONFIG_PM} else if (udev->state == USB_STATE_SUSPENDED &&udev->persist_enabled) {/* For a suspended device, treat this as a* remote wakeup event.*/usb_unlock_port(port_dev);status = usb_remote_wakeup(udev);usb_lock_port(port_dev);
#endif} else {/* Don't resuscitate */;}}clear_bit(port1, hub->change_bits);/* successfully revalidated the connection */if (status == 0)return;

如果之前没有不是只需要唤醒，就进入连接处理

 usb_unlock_port(port_dev);hub_port_connect(hub, port1, portstatus, portchange);usb_lock_port(port_dev);

hub_port_connect 函数接着处理连接相关事务。