On Sat Apr 5 02:45:01 PDT 2014, Daniel Vetter daniel.vetter@ffwll.ch 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.

[snip]

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++;

This function may be simplified by:

--- tda998x_drv.c~ +++ tda998x_drv.c @@ -568,11 +568,11 @@

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)

and the same may be done in hdmi.c:

diff --git a/drivers/video/hdmi.c b/drivers/video/hdmi.c index 9e758a8..b6c9030 100644 --- a/drivers/video/hdmi.c +++ b/drivers/video/hdmi.c @@ -31,14 +31,14 @@ static void hdmi_infoframe_checksum(void *buffer, size_t size) { u8 *ptr = buffer; - u8 csum = 0; + int csum = 0; size_t i;

/* compute checksum */ for (i = 0; i < size; i++) - csum += ptr[i]; + csum -= ptr[i];

- ptr[3] = 256 - csum; + ptr[3] = csum; }

/**