USB设备状态设置--usb_gadget_set_state（）.pdfVIP

USB设备状态设置--usb_gadget_set_state（）

一、USB设备状态

在USB2.0协议中第9.1USBDeviceStates章节规定了USB设

备的6种状态，包括：

Attached/Powered/Default/Address/Configured/Suspended

其状态迁移图如下：

在LinuxKernelch9.h文件中用enumusb_device_state来标记

这几种状态。

//kernel_dir/include/uapi/linux/usb/ch9.h

enumusb_device_state{

/*NOTATTACHEDisntintheUSBspec,andthisstateacts

*thesameasATTACHED...butitsclearerthisway.

*/

USB_STATE_NOTATTACHED=0,

/*chapter9andauthentication(wireless)devicestates*/

USB_STATE_ATTACHED,

USB_STATE_POWERED,/*wired*/

USB_STATE_RECONNECTING,/*auth*/

USB_STATE_UNAUTHENTICATED,/*auth*/

USB_STATE_DEFAULT,/*limitedfunction*/

USB_STATE_ADDRESS,

USB_STATE_CONFIGURED,/*mostfunctions*/

USB_STATE_SUSPENDED

/*NOTE:thereareactuallyfourdifferentSUSPENDED

*states,returningtoPOWERED,DEFAULT,ADDRESS,or

*CONFIGUREDrespectivelywhenSOFtokensflowagain.

*AtthisleveltheresnodifferencebetweenL1andL2

*suspendstates.(L2beingoriginalUSB1.1suspend.)

*/

};

二、状态设置函数usb_gadget_set_state()

//kernel_dir/drivers/usb/gadget/udc/udc-core.c

voidusb_gadget_set_state(structusb_gadget*gadget,

enumusb_device_statestate)

{

gadget-state=state;

schedule_work(gadget-work);

}

EXPORT_SYMBOL_GPL(usb_gadget_set_state);

//kernel_dir/include/linux/usb/gadget.h

externvoidusb_gadget_set_state(structusb_gadget*gadget,

enumusb_device_statestate);

在udc-core.c文件中，会去定义usb_gadget_set_state()函数，

将状态state的值赋值给gadget-state。其中structusb_gadget是

用来标记一个USB设备的信息。此时USB设备的状态就可以确定了。

之后启动工作队列schedule_work(gadget-work);将状态信息给

到sysfs。

在USB的枚