On Sat Apr 5 02:45:01 PDT 2014,
Daniel Vetter <daniel.vetter@xxxxxxxx> 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;
}
/**
--
Ken ar c'hentañ | ** Breizh ha Linux atav! **
Jef | http://moinejf.free.fr/
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