On Sun, 10 Nov 2024 at 11:29, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: > > 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. I am not against adding a feature like this, but we still need a way to notify userspace about a change of the privacy state when the user presses it. Controls are great for this. > > 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. I am curious who implements a software privacy switch. I would definitely use a physical cover in those devices. Chromebooks only support physical cover and hardware privacy switch. I have not seen software privacy switches. > > 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 > > > -- Ricardo Ribalda
