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authorDaniel Vetter <daniel.vetter@ffwll.ch>2014-04-05 18:24:29 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2014-04-22 15:39:41 +0200
commit8268bd48af9aae5e079d3ba8403ae459ff06cbcb (patch)
tree32c78eb6aad59e7976efa2d2c8ec0e17abedfd39 /drivers/gpu/drm
parente0c6a73fb191daad6d4ea808a89c6e22ac1b2733 (diff)
downloadop-kernel-dev-8268bd48af9aae5e079d3ba8403ae459ff06cbcb.zip
op-kernel-dev-8268bd48af9aae5e079d3ba8403ae459ff06cbcb.tar.gz
drm/i2c/tda998x: Fix signed overflow issue
This is C standard hair-splitting, but afaict - sum will be promoted to signed int in computation since uint8_t fits - signed overflow is undefined. No we need to add up an awful lot of bytes to actually make it overflow. But I guess the real risk is gcc spotting this and going bananas. Fix this by simply using unsigned in to force all computations to use the well-defined unsigned behaviour. Spotted by coverity. v2: Simplify the entire computation as suggested by Jean. Cc: Russell King <rmk+kernel@arm.linux.org.uk> Cc: Rob Clark <robdclark@gmail.com> Cc: Jean-Francois Moine <moinejf@free.fr> Reviewed-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm')
-rw-r--r--drivers/gpu/drm/i2c/tda998x_drv.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index 48af5ca..240c331 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -568,11 +568,11 @@ static irqreturn_t tda998x_irq_thread(int irq, void *data)
static uint8_t tda998x_cksum(uint8_t *buf, size_t bytes)
{
- uint8_t sum = 0;
+ int sum = 0;
while (bytes--)
- sum += *buf++;
- return (255 - sum) + 1;
+ sum -= *buf++;
+ return sum;
}
#define HB(x) (x)
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