Hi Steve, On Tue, Mar 14, 2017 at 09:43:09AM -0700, Steve Longerbeam wrote: > > > On 03/14/2017 09:21 AM, Nicolas Dufresne wrote: > >Le lundi 13 mars 2017 à 10:45 +0000, Russell King - ARM Linux a écrit : > >>On Mon, Mar 13, 2017 at 11:02:34AM +0100, Hans Verkuil wrote: > >>>On 03/11/2017 07:14 PM, Steve Longerbeam wrote: > >>>>The event must be user visible, otherwise the user has no indication > >>>>the error, and can't correct it by stream restart. > >>>In that case the driver can detect this and call vb2_queue_error. It's > >>>what it is there for. > >>> > >>>The event doesn't help you since only this driver has this issue. So nobody > >>>will watch this event, unless it is sw specifically written for this SoC. > >>> > >>>Much better to call vb2_queue_error to signal a fatal error (which this > >>>apparently is) since there are more drivers that do this, and vivid supports > >>>triggering this condition as well. > >>So today, I can fiddle around with the IMX219 registers to help gain > >>an understanding of how this sensor works. Several of the registers > >>(such as the PLL setup [*]) require me to disable streaming on the > >>sensor while changing them. > >> > >>This is something I've done many times while testing various ideas, > >>and is my primary way of figuring out and testing such things. > >> > >>Whenever I resume streaming (provided I've let the sensor stop > >>streaming at a frame boundary) it resumes as if nothing happened. If I > >>stop the sensor mid-frame, then I get the rolling issue that Steve > >>reports, but once the top of the frame becomes aligned with the top of > >>the capture, everything then becomes stable again as if nothing happened. > >> > >>The side effect of what you're proposing is that when I disable streaming > >>at the sensor by poking at its registers, rather than the capture just > >>stopping, an error is going to be delivered to gstreamer, and gstreamer > >>is going to exit, taking the entire capture process down. > >Indeed, there is no recovery attempt in GStreamer code, and it's hard > >for an higher level programs to handle this. Nothing prevents from > >adding something of course, but the errors are really un-specific, so > >it would be something pretty blind. For what it has been tested, this > >case was never met, usually the error is triggered by a USB camera > >being un-plugged, a driver failure or even a firmware crash. Most of > >the time, this is not recoverable. > > > >My main concern here based on what I'm reading, is that this driver is > >not even able to notice immediately that a produced frame was corrupted > >(because it's out of sync). From usability perspective, this is really > >bad. > > First, this is an isolated problem, specific to bt.656 and it only > occurs when disrupting the analog video source signal in some > way (by unplugging the RCA cable from the ADV718x connector > for example). > > Second, there is no DMA status support in i.MX6 to catch these > shifted bt.656 codes, and the ADV718x does not provide any > status indicators of this event either. So monitoring frame intervals > is the only solution available, until FSL/NXP issues a new silicon rev. > > > > Can't the driver derive a clock from some irq and calculate for > >each frame if the timing was correct ? > > That's what is being done, essentially. > > > And if not mark the buffer with > >V4L2_BUF_FLAG_ERROR ? > > I prefer to keep the private event, V4L2_BUF_FLAG_ERROR is too > unspecific. Is the reason you prefer an event that you have multiple drivers involved, or that the error flag is, well, only telling there was an error with a particular frame? Returning -EIO (by calling vb2_queue_error()) would be a better choice as it is documented behaviour. -- Regard,s Sakari Ailus e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx
