On Fri, Aug 02, 2013 at 09:16:03AM +0800, Aaron Lu wrote: > Hi Jani & Daniel, > > It turned out there is an integer overflow problem, and the below patch > fixed this problem on Acer Aspire 4732Z and thinkpad R61i. > > From: Aaron Lu <aaron.lu@xxxxxxxxx> > Subject: [PATCH] drm/i915: avoid brightness overflow when doing scale > > Some card's max brightness level is pretty large, e.g. on Acer Aspire > 4732Z, the max level is 989910. If user space set a large enough level > then the current scale done in intel_panel_set_backlight will cause an > integer overflow and the scaled level will be mistakenly small, leaving > user with an almost black screen. This patch fixes this problem. > > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> > --- > Since the only external user of intel_panel_set_backlight is operation > region code where the max will be a constant of 255, this patch fixes > the problem by comparing freq and max and then do things accordingly > instead of converting to 64 bits. Yeah, makes sense. Picked up for -fixes, thanks for the patch. -Daniel > > drivers/gpu/drm/i915/intel_panel.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c > index 67e2c1f..7c674f0 100644 > --- a/drivers/gpu/drm/i915/intel_panel.c > +++ b/drivers/gpu/drm/i915/intel_panel.c > @@ -498,7 +498,10 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level, u32 max) > } > > /* scale to hardware */ > - level = level * freq / max; > + if (freq < max) > + level = level * freq / max; > + else > + level = freq / max * level; > > dev_priv->backlight.level = level; > if (dev_priv->backlight.device) > -- > 1.8.3.1 > > > Hi Boris, > > Since the sysfs interface works on your system, I think your problem > should be different. Can you please file a bug for this? I can provide > you with a debug patch and then see what happened. Please attach > acpidump when filing the bug. > > https://bugzilla.kernel.org, ACPI/Power-Video. > > Thanks, > Aaron > > > > >> > >> The ranges are different, though: > >> > >> intel_backlight/actual_brightness:1000 > >> intel_backlight/bl_power:0 > >> intel_backlight/brightness:1000 > >> intel_backlight/max_brightness:4437 > >> intel_backlight/type:raw > >> > >> acpi_video0/actual_brightness:41 > >> acpi_video0/bl_power:0 > >> acpi_video0/brightness:41 > >> acpi_video0/max_brightness:100 > >> acpi_video0/type:firmware > > > > Yes, different interface has different brightness ranges and a value in > > one range may turn out to be the same actual brightness level of another > > value in another range. > > > >> > >> I guess I need to write me a dirty script for now ... :-) > > > > :-) > > > >> > >> Thanks guys. > >> > > Thanks, > > Aaron > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > > -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
