Re: [PATCH] drm: Call sysfs_notify after changing drm_connector::dpms

[Karsten Wiese <fzuuzf@xxxxxxxxxxxxxx>]

2017-09-25 15:48 GMT+02:00 Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>:

On Tue, 19 Sep 2017, Karsten Wiese <fzuuzf@xxxxxxxxxxxxxx> wrote:
> This makes poll work for the
> /sys/class/drm/cardX/connectorY/dpms attributes.

I guess the question is, what are you trying to achieve? What is the
problem that this solves?

​

The patch enables cpu cycle less waiting for dpms flag changes.

Here it lets a screen brightness ​setting daemon know which monitor to handle.

One of the attached screens gets confused if it is set just after being switched on,

hence the daemon leaves it untouched until it has been active for some seconds.

Without the p​atch the daemon would have to actively read the dpms flag every once in a while.

 

We have zero sysfs_notify in all of drm AFAICT. 

Yes I noticed too and looked for some dbus signal to listen to​ but didn't find any.

BR,

Karsten

BR,
Jani.

>
> Tested with i915 suspended by XScreenServer and
> suspend to RAM.
>
> Signed-off-by: Karsten Wiese <fzuuzf@xxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 4 ++++
>  drivers/gpu/drm/drm_atomic_helper.c | 6 +++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 2fd383d..b6fa87b 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1880,6 +1880,10 @@ int drm_atomic_connector_commit_dpms(struct drm_atomic_state *state,
>  out:
>       if (ret != 0)
>               connector->dpms = old_mode;
> +     else
> +             if (connector->dpms != old_mode)
> +                     sysfs_notify(&connector->kdev->kobj, NULL, "dpms");
> +
>       return ret;
>  }
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 4e53aae..6198772 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -921,12 +921,16 @@ drm_atomic_helper_update_legacy_modeset_state(struct drm_device *dev,
>               crtc = new_conn_state->crtc;
>               if ((!crtc && old_conn_state->crtc) ||
>                   (crtc && drm_atomic_crtc_needs_modeset(crtc->state))) {
> -                     int mode = DRM_MODE_DPMS_OFF;
> +                     int old_mode, mode = DRM_MODE_DPMS_OFF;
>
>                       if (crtc && crtc->state->active)
>                               mode = DRM_MODE_DPMS_ON;
>
> +                     old_mode = connector->dpms;
>                       connector->dpms = mode;
> +                     if (old_mode != mode)
> +                             sysfs_notify(&connector->kdev->kobj,
> +                                             NULL, "dpms");
>               }
>       }

--

Jani Nikula, Intel Open Source Technology Center

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