On 6/20/2013 11:20 AM, Chetan Nanda wrote:
Hi Laurent,
Thanks for your mail,
On Tue, Jun 18, 2013 at 6:12 PM, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
Hi Chetan,
On Tuesday 18 June 2013 11:17:40 Chetan Nanda wrote:
Hi,
I am currently working with UVC camera device which send data using
bulk transfer for preview and capture.
I have modified UVC gadget driver to start bulk streaming on receiving
first UVC_VS_COMMIT_CONTROL request from host side.
But currently not able to detect when to stop the streaming.
I am running Cheese Application on host side to test start/stop streaming.
UVC gadget driver's 'uvc_function_set_alt' function is getting called
when closing the cheese application, but this function is also
(sometime) getting called when starting the cheese application on HOST
side, also some time this function gets called after receiving first
COMMIT_CONTROL.
So, currently I am not able to find a proper way for starting /
stopping streaming for UVC bulk transfer.
Anyone has successfully implemented the start/stop streaming usecase
for bulk mode?
That's in my opinion one of the shortcomings of the UVC specification. There
is no explicit way to start streaming on bulk endpoints. One option would be
to start streaming when receiving the first IN token on the bulk endpoint, and
to stop streaming when no bulk activity has been detected for a given amount
of time. A bit hackish, but I'm not sure if there's any other practical way.
What is the limitation in defining bulk endpoint also under alt setting
1, similar to that of ISOC? Does USB specs prohibit to do that? If not,
then would it not insure set_alt when camera application at host PC is
started or stopped?
I am not sure what I am talking will really make sense. But, changing
dwc3 driver in hackish way can not be the final solution.
Regards
Pratyush
We are using DWC3 usb device controller and tried to look into the
dwc3 driver code to check a place where we can identify
first IN token from HOST side.
I tried modify 'dwc3_endpoint_interrupt' function in file
'drivers/usb/dwc3/gadget.c' in case 'case DWC3_DEPEVT_XFERNOTREADY:'
to start streaming for the first time when this case hit.
I am not sure if this is the right place for this,
I will dig more into the DWC3 spec and code.
Any pointer would be very helpful.
--
Regards,
Laurent Pinchart
Thanks,
Chetan Nanda
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