Hi Sakari, On 11/30/22 14:41, Sakari Ailus wrote: > Hi Hans, > > On Wed, Nov 30, 2022 at 12:11:44AM +0100, Hans de Goede wrote: >> Add support for a privacy-led GPIO. >> >> Making the privacy LED to controlable from userspace, as using the LED >> class subsystem would do, would make it too easy for spy-ware to disable >> the LED. >> >> To avoid this have the sensor driver directly control the LED. >> >> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> >> --- >> Note an additional advantage of directly controlling the GPIO is that >> GPIOs are tied directly to consumer devices. Where as with a LED class >> device, there would need to be some mechanism to tie the right LED >> (e.g front or back) to the right sensor. > > Thanks for the patch. > > This approach has the drawback that support needs to be added for each > sensor separately. Any idea how many sensor drivers might need this? Quite a few probably. But as discussed here I plan to write a generic sensor_power helper library since many sensor drivers have a lot of boilerplate code to get clks + regulators + enable/reset gpios. The plan is to add support for a "privacy-led" to this library so that all sensors which use this get support for free. Laurent pointed out that some sensors may have more complex power-up sequence demands, which is true. But looking at existing drivers then many follow a std simple pattern which can be supported in a helper-library. > Most implementations have privacy LED hard-wired to the sensor's power > rails so it'll be lit whenever the sensor is powered on. > > If there would be more than just a couple of these I'd instead create a LED > class device and hook it up to the sensor in V4L2. A LED cladd device will allow userspace to override the privacy-led value which is considered bad from a privacy point of view. This was actually already discussed here: https://lore.kernel.org/platform-driver-x86/e5d8913c-13ba-3b11-94bc-5d1ee1d736b0@xxxxxxxxxxxxxxxx/ See the part of the thread on the cover-letter with Dan, Laurent and me participating. And a LED class device also will be a challenge to bind to the right sensor on devices with more then one sensor, where as mentioned above using GPIO-mappings give us the binding to the right sensor for free. Regards, Hans
