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> -----Original Message----- > From: Intel-gfx [mailto:[email protected]] On Behalf Of > Eoff, Ullysses A > Sent: Thursday, November 20, 2014 9:34 AM > To: Nikula, Jani; [email protected] > Subject: Re: [Intel-gfx] [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: [email protected] > > 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 <[email protected]> > > 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/[email protected] > > Reference: https://bugzilla.kernel.org/show_bug.cgi?id=85861 > > Cc: U. Artie Eoff <[email protected]> > > Signed-off-by: Jani Nikula <[email protected]> > > Tested-by: U. Artie Eoff <[email protected]> > > > --- > > 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 > [email protected] > http://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
