Hi Sakari On Wed, 30 Oct 2024 at 15:25, Sakari Ailus <sakari.ailus@xxxxxx> wrote: > > Hi Ricardo, > > On Wed, Oct 30, 2024 at 02:03:18PM +0100, Ricardo Ribalda wrote: > > Hi Hans (de Goede, but others are welcome as well :) ) > > > > Some notebooks have a button to disable the camera (not to be mistaken > > with the mechanical cover). This is a standard GPIO linked to the > > camera via the ACPI table. > > > > 4 years ago we added support for this button in UVC via the Privacy control. > > This has two issues: > > - If the camera has its own privacy control, it will be masked > > - We need to power-up the camera to read the privacy control gpio. > > > > We tried to fix the power-up issues implementing "granular power > > saving" but it has been more complicated than anticipated.... > > > > Last year, we proposed a patchset to implement the privacy gpio as a > > subdevice https://lore.kernel.org/linux-media/20230111-uvc_privacy_subdev-v1-0-f859ac9a01e3@xxxxxxxxxxxx/ > > > > I think it is a pretty clean solution and makes sense to use a > > subdevice for something that is a sub device of the camera :). > > > > Before moving forward, Laurent and I would like to hear your opinion. > > I remember we discussed this and I wasn't very enthusiastic about the > proposal but thinking about it again, there are situations where this is > the only feasible solution, including on raw cameras with a privacy GPIO, > besides the first issue you brought up above. > > Regarding the second one, why would you need to power on the camera to get > the GPIO's value? In order to read the control, you need to open the device, and once you open the device the device is powered up: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/usb/uvc/uvc_v4l2.c#n621 In a perfect world it would only be powered up during streamon(), but uvc is a complicated monster: - We have delayed controls - We have buttons If we only power up the device during streamon those things would not work properly. I think I have a solution for delayed controls...assuming the device implements the standard properly. I have no solution to support buttons :(. Luckily not that many cameras have that today Regards! > > I'll review the set. > > While in the case of UVC it's fairly clear what the sub-device is related > to, but for the general case it'd be good to have an ancillary link there. > > -- > Regards, > > Sakari Ailus -- Ricardo Ribalda
