Hans Verkuil <hverkuil@xxxxxxxxx> writes: > On 03/11/2016 02:41 PM, Robert Jarzmik wrote: >> Hans Verkuil <hverkuil@xxxxxxxxx> writes: > One area where I would like to see some helper functions is with respect to > format/media bus processing. I played with this a little bit but it is surprisingly > hard to do. A lot of devices have all sorts of weird and wonderful exceptions > that make this quite problematic. I'm also worried about the initial probing, where the subdevice, be that an I2C sensor or something else has to be available, ie. the v4l2_async_notifier and its implications. >> Ah, that's a special case we need to discuss. >> I've written in the commit message a chapter about a "special port of this >> code". This is it. >> >> This usecase is when a user does the following : >> - set format to 1280x1024, RGB565 >> - REQBUF for MMAP buffers >> - QBUF, capture, DQBUF >> >> - then set format to 640x480, RGB565 >> => here the new format fits in the previously allocated video buffer >> - QBUF >> => the test in pxa_vb2_prepare() detects this, and calls pxa_buffer_init() >> again >> >> Now if this usecase is impossible, then I'll do as you say to simplify the code >> : use icd->sizeimage, remove the code in pxa_vb2_prepare(), etc ... > > Does this actually work with soc-camera? As far as I can see soc-camera returns > -EBUSY in soc_camera_s_fmt_vid_cap() if you attempt to change the format while > streaming. It's not "while streaming" in the described usecase, it's after streaming is finished actually. I should have added in the third dash VIDIOC_STREAMON before "capture" and VIDIOC_STREAMOFF after DQBUF. I think it's working, even if I had not tried recently. I certainly don't care that much about the usecase, and I won't feel sad dropping it :) > We theorized about this use-case, but nobody actually implemented it. > As far as I can see this use-case isn't supported today, so I would certainly not > implement it for this vb2 conversion. Fair enough, simpler is better, I'll remove it for v2. >>> If the latter, then just remove it. If you don't have the memory to allocate >>> the buffers, then reqbufs will just return ENOMEM. I never saw a reason for >>> such checks. >> Okay, that was to be consistent with former driver behavior. This was from the >> beginning in this driver. If Guennadi doesn't care, then I'll remove that, as he >> is the original author of this limitation. > > I've removed it from other drivers in the past, nobody complained :-) Good, let's do that here then. Cheers. -- Robert -- 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
