dpms mode change with wayland on iMX.6

[Pekka Paalanen]

On Mon, 27 May 2019 12:41:43 +0530
Pintu Agarwal <pintu.ping at gmail.com> wrote:

> Dear All,
> 
> I have a iMX.6 (arm 32) board with Linux Kernel 3.10 and debian
> platform running.
> The board is connected to one LCD screen and one HDMI monitor.
> It have DRM + Wayland setup for display.
> Also, I noticed that it have two dri interface:
> /dev/dri/card0
> /dev/dri/card1
> 
> I am not very familiar with Linux Graphics/Display subsystem, so I am
> looking for some help here.
> 
> My requirement is that I have turn off HDMI display screen using a
> command line utility or test program.
> I learn that for X-server we can use xset : xset dpms force off (and
> it works on my ubuntu desktop with 16.04).
> 
> However this command does not exists on my board.
> So, my question is:
> Is there any equivalent DPMS commands for Wayland/Wetson?

Hi,

there is not. A proper solution is to teach the display server (e.g.
Weston) toggle DPMS according to the conditions you need. If DPMS must
be controlled from outside of the display server, you have to invent
the necessary protocol extension (Wayland, D-Bus, something else...)
yourself.

> Then, when I try to run it using below command:
> # ./proptest.out 29 connector 2 3
> 
> The program just returns successfully without any errors, but nothing
> happens. The display does not turns off.
> I saw that in my kernel 3.10 the ioctl(DRM_IOCTL_MODE_SETPROPERTY) is
> already supported under DRM.
> 
> So, I am wondering what is the right way to verify DPMS mode property
> on wayland ?

You can probably read the property via DRM, but on DRM KMS there is no
way to set it unless you are the DRM master. The idea is that the
currently active display server is in control, and there is no way to
bypass it as long as it is active (is "DRM master").

Wayland is not a display server. Wayland is just an interface to some
display servers, and by design Wayland does not expose hardware knobs
like DPMS directly, unless you make your own Wayland extension for it.


Thanks,
pq
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