diff mbox series

media: qcom: use div64_u64() instead of do_div()

Message ID 1644395913-4091-1-git-send-email-wangqing@vivo.com
State New
Headers show
Series media: qcom: use div64_u64() instead of do_div() | expand

Commit Message

Qing Wang Feb. 9, 2022, 8:38 a.m. UTC
From: Wang Qing <wangqing@vivo.com>

do_div() does a 64-by-32 division.
When the divisor is u64, do_div() truncates it to 32 bits, this means it
can test non-zero and be truncated to zero for division.

fix do_div.cocci warning:
do_div() does a 64-by-32 division, please consider using div64_u64 instead.

Signed-off-by: Wang Qing <wangqing@vivo.com>
---
 drivers/media/platform/qcom/venus/vdec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Dmitry Baryshkov Feb. 10, 2022, 10:16 a.m. UTC | #1
On 09/02/2022 11:38, Qing Wang wrote:
> From: Wang Qing <wangqing@vivo.com>
> 
> do_div() does a 64-by-32 division.
> When the divisor is u64, do_div() truncates it to 32 bits, this means it
> can test non-zero and be truncated to zero for division.
> 
> fix do_div.cocci warning:
> do_div() does a 64-by-32 division, please consider using div64_u64 instead.


NAK

The div64_u64 is not equivalent to do_div. It returns the quotient
rather than modifying the first arg. Moreover it is unoptimal on 32-bit
arches.

> 
> Signed-off-by: Wang Qing <wangqing@vivo.com>
> ---
>   drivers/media/platform/qcom/venus/vdec.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
> index 91da3f5..941a904
> --- a/drivers/media/platform/qcom/venus/vdec.c
> +++ b/drivers/media/platform/qcom/venus/vdec.c
> @@ -435,7 +435,7 @@ static int vdec_s_parm(struct file *file, void *fh, struct v4l2_streamparm *a)
>   		return -EINVAL;
>   
>   	fps = (u64)USEC_PER_SEC;
> -	do_div(fps, us_per_frame);
> +	div64_u64(fps, us_per_frame);
>   
>   	inst->fps = fps;
>   	inst->timeperframe = *timeperframe;
diff mbox series

Patch

diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
index 91da3f5..941a904
--- a/drivers/media/platform/qcom/venus/vdec.c
+++ b/drivers/media/platform/qcom/venus/vdec.c
@@ -435,7 +435,7 @@  static int vdec_s_parm(struct file *file, void *fh, struct v4l2_streamparm *a)
 		return -EINVAL;
 
 	fps = (u64)USEC_PER_SEC;
-	do_div(fps, us_per_frame);
+	div64_u64(fps, us_per_frame);
 
 	inst->fps = fps;
 	inst->timeperframe = *timeperframe;