[PATCH] drm: Add DPMS ioctl

[Alex Ivanov]

On 11.10.2017 13:13, Daniel Stone wrote:
> I'm sorry, but this is not the right way to go about things. If Xorg
> or GNOME Shell or Weston or whatever thinks the monitor is DPMS-off,
> the fact that someone else has forcibly switched it back on will not
> make them continue painting.
User should disable DPMS management of display server
before using this ioctl.
> Conversely, if they are painting and
> someone does DPMS-off from underneath them, they'll keep painting
> anyway: if they're using the legacy API that means the display will
> switch straight back on, and if they're using atomic that means their
> commits will suddenly fail for an unknown reason and they'll be very
> confused.
That's sad to hear. Is that the reason why xf86-video-intel driver
switches the display back on, while modesetting driver doesn't
do anything? DPMS is disabled in X.Org config.
> If people are doing fancy new compositors without DPMS support, then I
> recommend they use an existing compositor base, such as libweston
> (others are also available) which actually implement DPMS. For
> Electron apps, there are a number of idle-inhibition options available
> for X11, and also for Wayland when that support lands in Electron.
> Unfortunately I don't think there is any way to just route around the
> compositor as this patch does.
libweston is still too tied to Weston at this moment, and other
libraries are still underway.

Your phrase is a great marker of how much complexity and
trickery for user is added into display power management
in comparison to power management of other components.
>
> Cheers,
> Daniel