Re: g_webcam Isoch high bandwidth transfer

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Hi Bin,

On 2016/9/23 4:11, Bin Liu wrote:
+Fengwei Yin per his request.
Thanks a lot for adding me to this thread.


On Thu, Sep 22, 2016 at 10:48:40PM +0300, Felipe Balbi wrote:

Hi,

Bin Liu <b-liu@xxxxxx> writes:

[...]

Here's one that actually compiles, sorry about that.

No worries, I was sleeping ;-)

I will test it out early next week. Thanks.

meanwhile, how about some instructions on how to test this out myself?
How are you using g_webcam and what are you running on host side? Got a
nice list of commands there I can use? I think I can get to bottom of
this much quicker if I can reproduce it locally ;-)
I am using similar use case with a different gadget function driver.

On device side:
- first patch g_webcam as in my first email in this thread to enable
  640x480@30fps;
- # modprobe g_webcam streaming_maxpacket=3072
- then run uvc-gadget to feed the YUV frames;
	http://git.ideasonboard.org/uvc-gadget.git
- I am using uvc function driver  + configfs.
- maxpacket in configfs was set to 3072.
- uvc-gadget from the same source as Bin.

On host side:
- first check the device ep descriptor, which should be
	wMaxPacketSize     0x1400  3x 1024 bytes
- then use luvcview or yavta to capture the video stream
- lsusb give me same wMaxPacketSize.
- I am using example (changed a little bit) from libuvc.

Regards
Yin, Fengwei


Capture the bus trace to check if multiple IN transactions happens in
each SOF.

The data buffer size in the usb_request coming from the uvc driver is
5120 bytes, so there should be 3 IN transactions if the UDC works
correctly.

Regards,
-Bin.

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