On 10/11/2024 11:02, Mauro Carvalho Chehab wrote: > Em Sat, 9 Nov 2024 17:29:54 +0100 > Ricardo Ribalda <ribalda@xxxxxxxxxxxx> escreveu: > >>> >>> I think that should sort the issue, assuming that 1. above holds true. >>> >>> One downside is that this stops UVC button presses from working when >>> not streaming. But userspace will typically only open the /dev/video# >>> node if it plans to stream anyways so there should not be much of >>> a difference wrt button press behavior. >> >> I do not personally use the button, but it is currently implemented as >> a standard HID device. > > IMO, controlling the privacy via evdev is the best approach then. There's > no need for a RW control neither at subdev or at device level. It could > make sense a Read only to allow apps to read, but still it shall be up to > the Kernel to protect the stream if the button is pressed. > >> Making it only work during streamon() might be >> a bit weird. >> I am afraid that if there is a button we should keep the current behaviour. > > Privacy matters only when streaming. IMO the Kernel check for it needs to > be done at DQBUF time and at read() calls, as one can enable/disable the > camera while doing videoconf calls. I do that a lot with app "soft" buttons, > and on devices that physically support cutting the video. We could add a vb2_s_privacy(bool privacy) function to vb2 to tell vb2 if the privacy mode is on. And if so, take action. E.g. calling QBUF/DQBUF would return a -EACCES error. That will ensure consistent behavior for all drivers that have a privacy function. Note that there are two types of privacy GPIO: one that triggers when a physical cover is moved, blocking the sensor, and one that is a button relying on software to stop streaming video. In the first case it is informative, but you can keep streaming. Regards, Hans > > I don't trust myself privacy soft buttons, specially when handled in userspace, > so what I have are webcam covers (and a small stick glued at a laptop camera > that has a too small sensor for a webcam cover). I only remove the cover/stick > when I want to participate on videoconf with video enabled with the builtin > camera. > > Regards > > Thanks, > Mauro >
