From: Jani Nikula <jani.nikula@linux.intel.com>
To: clinton.a.taylor@intel.com, Intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: Allow minimum brightness upon backlight enable
Date: Fri, 02 Oct 2015 10:50:50 +0300 [thread overview]
Message-ID: <87vbapaeud.fsf@intel.com> (raw)
In-Reply-To: <1443742613-24748-1-git-send-email-clinton.a.taylor@intel.com>
On Fri, 02 Oct 2015, clinton.a.taylor@intel.com wrote:
> From: Clint Taylor <clinton.a.taylor@intel.com>
>
> backlight minimum is a valid value so you don't need to set maximum.
>
> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
> ---
> drivers/gpu/drm/i915/intel_panel.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 4d28c7b..d509904 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1069,7 +1069,7 @@ void intel_panel_enable_backlight(struct intel_connector *connector)
>
> WARN_ON(panel->backlight.max == 0);
>
> - if (panel->backlight.level <= panel->backlight.min) {
> + if (panel->backlight.level < panel->backlight.min) {
> panel->backlight.level = panel->backlight.max;
> if (panel->backlight.device)
> panel->backlight.device->props.brightness =
This is policy in action in the kernel. We have this whole if block here
because some, uh, misguided userspace sets brightness to minimum before
switching the backlight off, and assumes enabling backlight cranks up
the brightness as well. (*)
The condition used to be (level == 0), but since the minimum can now
also be non-zero, we check (level <= min). If we changed this to (level
< min), we'd regress the misguided userspaces, especially if min == 0.
See
commit 13f3fbe827d09e3182023c8c54058cbf97aa146e
Author: Jeremiah Mahler <jmmahler@gmail.com>
Date: Mon Jan 12 11:01:03 2015 -0800
drm/i915: fix inconsistent brightness after resume
I'd really love to to just nuke the if block completely, but no
regressions and all.
BR,
Jani.
(*) Imagine an amplifier that would set the volume to max if it was
powered on with the volume knob turned to zero...
--
Jani Nikula, Intel Open Source Technology Center
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next prev parent reply other threads:[~2015-10-02 7:47 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-01 23:36 [PATCH] drm/i915: Allow minimum brightness upon backlight enable clinton.a.taylor
2015-10-02 7:50 ` Jani Nikula [this message]
2015-10-02 9:00 ` Chris Wilson
2015-10-20 10:32 ` Jani Nikula
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