Re: uvc-gadget for UVC testing doesn't seem to work with vivid

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Hi,

Rail Shafigulin <rail@xxxxxxxxxxxxxxx> writes:
>>>>> Let me apologize for emailing directly to the list as I'm not one of
>>>>> the developers and just starting out with USB and UVC. After searching
>>>>
>>>> the list is open to anybody and we welcome newcomers :-)
>>>>
>>>>> online for about a week I just couldn't find answers and I hope the
>>>>> original authors of the uvc-gadget tool are on the list and can help
>>>>> out.
>>>>>
>>>>> Needed to test a UVC in a custom built kernel (Xilinx petalinux), .
>>>>> Followed these directions,
>>>>> https://github.com/torvalds/linux/blob/ef954844c7ace62f773f4f23e28d2d915adc419f/Documentation/usb/gadget-testing.txt#L717-L730.
>>>>>
>>>>> Patches didn't work. Had to look around for correct ones. Found them
>>>>> here, http://markmail.org/message/hb7evzvigbuxptz5#query:+page:1+mid:s73fdeffjgb2v2yw+state:results.
>>>>>
>>>>> Combined and applied the patches into a repo here,
>>>>> https://github.com/cyboflash/uvc-gadget.git.
>>>>>
>>>>> When I ran a test command, given in the instructions above,
>>>>> uvc-gadget -u /dev/video<uvc video node #> -v /dev/video<vivid video node #>
>>>>>
>>>>> got the following error:
>>>>> V4L2_CORE: (jpeg decoder) error while decoding frame
>>>>>
>>>>> and a black screen.
>>>>>
>>>>> One thing to note is that I was not using luvcview, but guvcview.
>>>>>
>>>>> It looks like the error is coming from here,
>>>>> https://sourceforge.net/p/guvcview/git-master/ci/master/tree/gview_v4l2core/jpeg_decoder.c#l1503
>>>>>
>>>>> My thoughts
>>>>> 1. I don't think the error is coming from v4l2. I tested it on another
>>>>> machine and it worked. But I'm not an expert so I can't say for sure.
>>>>> 2. I don't think the error is coming from UVC. I think since I see a
>>>>> black screen, it is working. Again, I'm not an expert, so I can't say
>>>>> for sure.
>>>>> 3. I think the error is due to uvc-gadget test application. It could
>>>>> be that the applied patches are outdated, but I just didn't find
>>>>> anything else online. But, I'm not an expert so definitely can't say
>>>>> for sure.
>>>>>
>>>>> I would greatly appreciate any help with this as I'm just starting out
>>>>> with UVC and USB.
>>>>
>>>> Which kernel are you using? Which UDC driver are you using?
>>>
>>> Balbi,
>>>
>>> The board is configured as a USB Camera Gadget. Here is the output of uname -a
>>> Linux Xilinx-ZCU102-2016_3 4.6.0 #33 SMP Thu Aug 10 11:47:57 PDT 2017
>>> aarch64 GNU/Linux
>>
>> okay, then you need to ask for support from whoever gave you this
>> kernel. 4.6 is a really old release which this forum doesn't support.
>>
>>> When you say UDC (USB Device Controller) driver, what exactly do you mean?
>>
>> which driver is g_webcam binding to? What do you have under
>> /sys/class/udc ?
>
> I have this under /sys/class/udc
>
> fe200000.dwc3
>
> under /sys/class/udc/fe200000.dwc3

okay. Test against mainline and I can help you; otherwise you need to go
after Xilinx or whoever gave you this v4.6 kernel.

-- 
balbi

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