On Sat, 26 Feb 2011, Hans Verkuil wrote: > On Friday, February 25, 2011 18:08:07 Guennadi Liakhovetski wrote: > > <snip> > > > > > configure the sensor to react on an external trigger provided by the flash > > > > controller is needed, and that could be a control on the flash sub-device. > > > > What we would probably miss is a way to issue a STREAMON with a number of > > > > frames to capture. A new ioctl is probably needed there. Maybe that would be > > > > an opportunity to create a new stream-control ioctl that could replace > > > > STREAMON and STREAMOFF in the long term (we could extend the subdev s_stream > > > > operation, and easily map STREAMON and STREAMOFF to the new ioctl in > > > > video_ioctl2 internally). > > > > > > How would this be different from queueing n frames (in total; count > > > dequeueing, too) and issuing streamon? --- Except that when the last frame > > > is processed the pipeline could be stopped already before issuing STREAMOFF. > > > That does indeed have some benefits. Something else? > > > > Well, you usually see in your host driver, that the videobuffer queue is > > empty (no more free buffers are available), so, you stop streaming > > immediately too. > > This probably assumes that the host driver knows that this is a special queue? > Because in general drivers will simply keep capturing in the last buffer and not > release it to userspace until a new buffer is queued. Yes, I know about this spec requirement, but I also know, that not all drivers do that and not everyone is happy about that requirement:) > That said, it wouldn't be hard to add some flag somewhere that puts a queue in > a 'stop streaming on last buffer capture' mode. No, it wouldn't... But TBH this doesn't seem like the most elegant and complete solution. Maybe we have to think a bit more about it - which soncequences switching into the snapshot mode has on the host driver, apart from stopping after N frames. So, this is one of the possibilities, not sure if the best one. Thanks Guennadi --- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/ -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
