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@intel.com 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@intel.com
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.
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