On Mon 2017-03-13 10:45:38, Russell King - ARM Linux wrote: > 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. > > This severely restricts the ability to be able to develop and test > sensor drivers. Well, but kernel should do what is best for production, not what is best for driver debugging. And yes, I guess you can have #ifdef or module parameter or something switching for behaviour you prefer when you are debugging. But for production, vb2_queue_error() seems to be the right solution. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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