Hi, On Mon, Oct 2, 2023 at 8:48 AM Johan Hovold <johan@xxxxxxxxxx> wrote: > > > In any case, the fact that there is a shared power rail / shared power > > sequence is because the hardware designer intended them to either be > > both off or both on. Whenever I asked the EEs that designed these > > boards about leaving the touchscreen on while turning the panel power > > off they always looked at me incredulously and asked why I would ever > > do that. Although we can work around the hardware by powering the > > panel in order to allow the touchscreen to be on, it's just not the > > intention. > > I hear you, but users sometimes want do things with their hardware which > may not have originally been intended (e.g. your kiosk example). ...and they can. I don't think it's totally unreasonable for userspace in this case to take into account that they need to keep the panel powered on (maybe with the screen black and the backlight off) if they want the touchscreen kept on. If I was coding up userspace it wouldn't surprise me at all if the touchscreen stopped working when the panel was off. I will further note that there is actually hardware where it's even more difficult. On the same sc7180-trogdor laptops (and others as well) the USB webcam is _also_ powered by the same power rail. When you power the screen off then the USB webcam deenumerates. When you power the screen on then it shows back up. It would be really weird if somehow the USB webcam driver needed a link to the panel to try to keep it powered. -Doug
