AnsweredAssumed Answered

g_webcam gadget on IMX6

Question asked by Matthieu Vanin Employee on Nov 12, 2013
Latest reply on Jun 14, 2016 by tom gao



In the project to develop a webcam functionality on an IMX6 device, I would like to first test the basics through the g_webcam gadget and the UVC gadget test application.


Setup is:


Host: PC running Ubuntu 12.04 (kernel 3.5)

Device: IMX6 SabreSD device running a kernel version 3.0.35 (Ubuntu 11.04 File System) , g_webcam gadget loaded successfully (/dev/video0 created), and the test app (from git://
running through uvc-gadget –d /dev/video0

Device connected to the host through its USB OTG interface.



On my host, the USB device (gadget webcamera) is correctly seen, but it seems that at  the end the init is failing (uvc_video_init() failing) and so uvc_probe is failing.


[ 1948.348158] usb 1-1: new high-speed USB device number 4 using ehci_hcd

[ 1948.713758] usb 1-1: New USB device found, idVendor=1d6b, idProduct=0102

[ 1948.713763] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0

[ 1948.713767] usb 1-1: Product: Webcam gadget

[ 1948.713770] usb 1-1: Manufacturer: Linux Foundation

[ 1948.724520] uvcvideo: Probing generic UVC device 1

[ 1948.724526] uvcvideo: Found format YUV 4:2:2 (YUYV).

[ 1948.724529] uvcvideo: - 640x360 (15.0 fps)

[ 1948.724532] uvcvideo: - 1280x720 (2.0 fps)

[ 1948.724534] uvcvideo: Found format MJPEG.

[ 1948.724537] uvcvideo: - 640x360 (15.0 fps)

[ 1948.724540] uvcvideo: - 1280x720 (2.0 fps)

[ 1948.724544] uvcvideo: Found a Status endpoint (addr81).

[ 1948.724546] uvcvideo: Found UVC 1.00 device Webcam gadget (1d6b:0102)

[ 1948.724552] uvcvideo: Added control 00000000-0000-0000-0000-000000000001/2 to device 1 entity 1

[ 1948.724555] uvcvideo: Adding mapping 'Exposure, Auto' to control 00000000-0000-0000-0000-000000000001/2.

[ 1948.724559] uvcvideo: Added control 00000000-0000-0000-0000-000000000101/2 to device 1 entity 2

[ 1948.724562] uvcvideo: Adding mapping 'Brightness' to control 00000000-0000-0000-0000-000000000101/2.

[ 1948.724565] uvcvideo: Scanning UVC chain: OT 3 <- PU 2 <- IT 1

[ 1948.724569] uvcvideo: Found a valid video chain (1 -> 3).

[ 1953.724337] uvcvideo: UVC non compliance - GET_DEF(PROBE) not supported. Enabling workaround.

[ 1958.724420] uvcvideo: Failed to query (129) UVC probe control : -110 (exp. 26).

[ 1958.724427] uvcvideo: Failed to initialize the device (-5).


On my IMX6 device, I see from the test app that  I am receiving some request (UVC_GET_DEF => req 87) that seems to be answered, I see a response through Wireshark, but for some reason it is marked as
Malformed packet there.


On my device I have the following traces from the test app.


open succeeded, file descriptor = 3

device is fsl-usb2-udc on bus gadget

bRequestType a1 bRequest 87 wValue 0100 wIndex 0001
wLength 001a

streaming request (req 87 cs 01)


and from a dmesg on the IMX6 device:

g_webcam gadget: uvc_function_bind

g_webcam gadget: Webcam Video Gadget

g_webcam gadget: g_webcam ready

Suspend udc for OTG auto detect

USB Gadget resume begins

fsl_udc_resume, Wait for wakeup thread finishes

dr_controller_run: udc out low power mode

USB Gadget resume ends

fsl-usb2-udc: bind to driver g_webcam

fsl_gadget_disconnect_event: udc enter low power mode

USB Charger Disconnected.

otg udc vbus rising wakeup

try_wake_up_udc: udc out low power mode

USB Charger Connected.

g_webcam gadget: high speed config #1: Video

g_webcam gadget: uvc_function_set_alt(0, 0)

g_webcam gadget: uvc_function_set_alt(1, 0)

g_webcam gadget: uvc_function_set_alt(1, 0)

g_webcam gadget: uvc_function_set_alt(1, 0)


Before I start adding traces almost everywhere ;-), is there someone who may already have faced similar issue? Did people already used the g_webcam gadget on the IMX6 SabreSD or any IMX6 based board?


Could it be any compatibility problem between my host running a kernel 3.5 and my device running a kernel 3.0? Some old known bugs I am missing fixes in the old kernels I am using? Is there something not correctly configured from the application side? I am pretty new to the USB / V4L2 and UVC, so is there something special I should check first?


Thanks & Regards