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." > 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, Laurent Pinchart -- 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
