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| author | Aaron Lu <aaron.lu@intel.com> | 2013-08-02 09:16:03 +0800 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2013-08-07 11:57:08 +0200 |
| commit | 22505b82a2800bddb67908522833bef96dd15845 (patch) | |
| tree | 40de131f1ed5a141107afccfaf2ab7a6db0ba535 /drivers/gpu/drm/i915/intel_panel.c | |
| parent | 9dbd8febb4dbc9199fcf340b882eb930e36b65b6 (diff) | |
| download | lwn-22505b82a2800bddb67908522833bef96dd15845.tar.gz lwn-22505b82a2800bddb67908522833bef96dd15845.zip | |
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>
[danvet: Add a comment to explain what's going on.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/i915/intel_panel.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_panel.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index 67e2c1f1c9a8..5063eadac3ef 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -497,8 +497,11 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level, u32 max) goto out; } - /* scale to hardware */ - level = level * freq / max; + /* scale to hardware, but be careful to not overflow */ + if (freq < max) + level = level * freq / max; + else + level = freq / max * level; dev_priv->backlight.level = level; if (dev_priv->backlight.device) |