On Tue, 02 Dec 2014, "Eoff, Ullysses A" <ullysses.a.eoff@xxxxxxxxx> wrote: > bump Talked about this with Daniel a while back, his take was, "preemptively catering to bonghits userspace means we'll have less wiggle-room in the future" BR, Jani. > >> -----Original Message----- >> From: Intel-gfx [mailto:intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx] On Behalf Of Eoff, Ullysses A >> Sent: Thursday, November 20, 2014 9:34 AM >> To: Nikula, Jani; intel-gfx@xxxxxxxxxxxxxxxxxxxxx >> Subject: Re: [RFC PATCH] drm/i915: avoid round-trip scaling errors in actual_brightness >> >> > -----Original Message----- >> > From: Nikula, Jani >> > Sent: Thursday, November 20, 2014 3:59 AM >> > To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx >> > Cc: Nikula, Jani; Eoff, Ullysses A >> > Subject: [RFC PATCH] drm/i915: avoid round-trip scaling errors in actual_brightness >> > >> > Due to scaling, the userspace and hardware brightness ranges might not >> > have a 1:1 mapping, causing the backlight class sysfs actual_brightness >> > not match the brightness attribute just written. While this is not a >> > strict requirement per Documentation/ABI/stable/sysfs-class-backlight, >> > try the userspace->hardware scaling for a match first and return the >> > cached value to not confuse userspace. >> > >> > The problem was already mitigated by >> > >> > commit 673e7bbdb3920b62cfc6c710bea626b0a9b0f43a >> > Author: U. Artie Eoff <ullysses.a.eoff@xxxxxxxxx> >> > Date: Mon Sep 29 15:49:32 2014 -0700 >> > >> > drm/i915: intel_backlight scale() math WA >> > >> > but this should be more robust for cases where the userspace expects >> > actual_brightness to match the just written brightness. >> > >> > Reference: http://mid.gmane.org/1415737838-9640-1-git-send-email-ullysses.a.eoff@xxxxxxxxx >> > Reference: https://bugzilla.kernel.org/show_bug.cgi?id=85861 >> > Cc: U. Artie Eoff <ullysses.a.eoff@xxxxxxxxx> >> > Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> >> >> Tested-by: U. Artie Eoff <ullysses.a.eoff@xxxxxxxxx> >> >> > --- >> > drivers/gpu/drm/i915/intel_panel.c | 12 +++++++++++- >> > 1 file changed, 11 insertions(+), 1 deletion(-) >> > >> > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c >> > index 4d63839bd9b4..675b56e105e7 100644 >> > --- a/drivers/gpu/drm/i915/intel_panel.c >> > +++ b/drivers/gpu/drm/i915/intel_panel.c >> > @@ -1024,7 +1024,17 @@ static int intel_backlight_device_get_brightness(struct backlight_device *bd) >> > drm_modeset_lock(&dev->mode_config.connection_mutex, NULL); >> > >> > hw_level = intel_panel_get_backlight(connector); >> > - ret = scale_hw_to_user(connector, hw_level, bd->props.max_brightness); >> > + >> > + /* >> > + * Check the userspace->hardware scaling for a match first to avoid >> > + * scaling errors in the userspace->hardware->userspace round-trip. >> > + */ >> > + if (hw_level == scale_user_to_hw(connector, bd->props.brightness, >> > + bd->props.max_brightness)) >> > + ret = bd->props.brightness; >> > + else >> > + ret = scale_hw_to_user(connector, hw_level, >> > + bd->props.max_brightness); >> > >> > drm_modeset_unlock(&dev->mode_config.connection_mutex); >> > intel_runtime_pm_put(dev_priv); >> > -- >> > 2.1.3 >> >> _______________________________________________ >> Intel-gfx mailing list >> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx >> http://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
