On 04/05/2014 02:45 AM, Daniel Vetter wrote:
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
^^ Now
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.
Seems reasonable... it also seems impossible (ha!) to break anything.
Reviewed-by: Ian Romanick ian.d.romanick@intel.com
Spotted by coverity.
Cc: Russell King rmk+kernel@arm.linux.org.uk Cc: Rob Clark robdclark@gmail.com Cc: Jean-Francois Moine moinejf@free.fr Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch
drivers/gpu/drm/i2c/tda998x_drv.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c index 48af5cac1902..ae2754760d77 100644 --- a/drivers/gpu/drm/i2c/tda998x_drv.c +++ b/drivers/gpu/drm/i2c/tda998x_drv.c @@ -568,7 +568,7 @@ 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;
unsigned sum = 0;
while (bytes--) sum += *buf++;