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author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2014-04-05 18:24:29 +0200 |
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committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2014-04-22 15:39:41 +0200 |
commit | 8268bd48af9aae5e079d3ba8403ae459ff06cbcb (patch) | |
tree | 32c78eb6aad59e7976efa2d2c8ec0e17abedfd39 /drivers/gpu/drm | |
parent | e0c6a73fb191daad6d4ea808a89c6e22ac1b2733 (diff) | |
download | op-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.c | 6 |
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) |