I recompile v4.4 kernel with
CONFIG_MEDIA_SUPPORT=y
CONFIG_MEDIA_CAMERA_SUPPORT=y
CONFIG_VIDEO_V4L2=y
CONFIG_MEDIA_USB_SUPPORT=y
CONFIG_USB_VIDEO_CLASS=y
CONFIG_USB_VIDEO_CLASS_INPUT_EVDEV=y
CONFIG_USB_GSPCA=y
CONFIG_USB_PWC=y
CONFIG_USB_PWC_DEBUG=y
CONFIG_USB_PWC_INPUT_EVDEV=y
and connect my usb camera using a OTG line, then get this
Nov 18 07:59:06 sdcard kernel: usb 1-1: new high-speed USB device number 2 using dwc2
Nov 18 07:59:06 sdcard kernel: hub 1-1:1.0: USB hub found
Nov 18 07:59:06 sdcard kernel: hub 1-1:1.0: 3 ports detected
Nov 18 07:59:06 sdcard kernel: usb 1-1.1: new high-speed USB device number 3 using dwc2
Nov 18 07:59:06 sdcard kernel: uvcvideo: Found UVC 1.00 device USB2.0 Camera (1871:01f0)
Nov 18 07:59:06 sdcard kernel: input: USB2.0 Camera as /devices/platform/soc/f72c0000.usb/usb1/1-1/1-1.1/1-1.1:1.0/input/input0
I get the webcam display by excute mplayer tv:// and the transfer speed seems to be very low, the fps is 4 and sometimes is 1.