Hi, > On Thu, Jul 4, 2013 at 1:53 AM, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Pratyush, > On Tuesday 02 July 2013 17:24:41 Pratyush Anand wrote: >> On 6/20/2013 11:20 AM, Chetan Nanda wrote: > >> On Tue, Jun 18, 2013 at 6:12 PM, Laurent Pinchart wrote: > >>> 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? > The UVC specification does, unfortunately. UVC 1.1 section 2.4.3 states > "A VideoStreaming interface containing a bulk endpoint for streaming shall > support only alternate setting zero. Additional alternate settings containing > bulk endpoints are not permitted in a device that is compliant with the Video > Class specification." Sorry, I have been away from the UVC gadget for too long now. I had posted a patchset in the past that worked for me on Bulk IN video streaming endpoint (see [1]). I have to sent out a V2 of this patchset, but I will be able to do so only after 2-3 weeks from now. I hope Chetan can try to apply this patch and test this Bulk video streaming using cheese application on a linux host on his platform as well. [1] http://comments.gmane.org/gmane.linux.usb.general/85292 Regards, Bhupesh >> 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. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
