Hi Laurent, On Fri, May 03, 2013 at 01:20:15AM +0200, Laurent Pinchart wrote: [snip] > I'm open to suggestions :-) What features of the userspace application do you > think could (and should) be moved to kernelspace ? Many of them are highly > application-specific. All UVC_EVENTS beneath STREAMON and STREAMOFF could go into the kernelspace. I have seen such codepath: [1] v4l2_event_queue /* kernelspace */ v4l2_event_dequeue /* kernelspace */ uvc_events_process_setup /* userspace */ uvc_events_process_class /* userspace */ uvc_events_process_streaming /* userspace */ uvc_fill_streaming_control /* userspace */ The codepath [1] is needed to respond with the possible supported streaming capabilities. That information really should come from the uvc_descriptor_header. We already have this information in the kernel, there is no need for redundancy. [2] v4l2_event_queue /* kernelspace */ v4l2_event_dequeue /* kernelspace */ uvc_events_process_data /* userspace */ /* in case of UVC_VS_COMMIT_CONTROL */ uvc_video_set_format /* kernelspace */ uvc_v4l2_do_ioctl /* kernelspace */ The codepath [2] is really odd, as we jump out of the kernel back into the kernel just to gather some information about the requested videoformat by the host. The application itself should call the ioctl VIDIOC_G_FMT on UVC_EVENT_STREAMON and change its videosetup likewise. This should be possible with gstreamer. I currently work on an derived version of the gstv4l2sink -> gstv4l2uvcsink to handle the uvc specialities. And addressing the initial problem with the missing userspace application; The gadget can loose its dependency to it, if the kernel would produce dummy frames with the requested format and switch over to the real streaming data, when opened. Just my two cents, Michael -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- 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
