linux-kernel - [PATCH] media: iris: Fix fps calculation

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Message-Id: <20251013-iris-v1-1-6242a8c82ff7@chromium.org>
Date: Mon, 13 Oct 2025 14:13:36 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Vikash Garodia <vikash.garodia@....qualcomm.com>, 
 Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>, 
 Abhinav Kumar <abhinav.kumar@...ux.dev>, Bryan O'Donoghue <bod@...nel.org>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Hans Verkuil <hverkuil+cisco@...nel.org>
Cc: linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH] media: iris: Fix fps calculation

iris_venc_s_param() uses do_div to divide two 64 bits operators, this is
wrong. Luckily for us, both of the operators fit in 32 bits, so we can use
a normal division.

Now that we are at it, mark the fps smaller than 1 as invalid, the code
does not seem to handle them properly.

The following cocci warning is fixed with this patch:
./platform/qcom/iris/iris_venc.c:378:1-7: WARNING: do_div() does a 64-by-32 division, please consider using div64_u64 instead

Fixes: 4ff586ff28e3 ("media: iris: Add support for G/S_PARM for encoder video device")
Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
---
 drivers/media/platform/qcom/iris/iris_venc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/qcom/iris/iris_venc.c b/drivers/media/platform/qcom/iris/iris_venc.c
index 099bd5ed4ae0294725860305254c4cad1ec88d7e..1234c61d9e44c632b065a5c44d3290f6e1491892 100644
--- a/drivers/media/platform/qcom/iris/iris_venc.c
+++ b/drivers/media/platform/qcom/iris/iris_venc.c
@@ -371,11 +371,10 @@ int iris_venc_s_param(struct iris_inst *inst, struct v4l2_streamparm *s_parm)
 	us_per_frame = timeperframe->numerator * (u64)USEC_PER_SEC;
 	do_div(us_per_frame, timeperframe->denominator);
 
-	if (!us_per_frame)
+	if (!us_per_frame || us_per_frame > USEC_PER_SEC)
 		return -EINVAL;
 
-	fps = (u64)USEC_PER_SEC;
-	do_div(fps, us_per_frame);
+	fps = USEC_PER_SEC / (u32)us_per_frame;
 	if (fps > max_rate) {
 		ret = -ENOMEM;
 		goto reset_rate;

---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251013-iris-9addbd27ef76

Best regards,
-- 
Ricardo Ribalda <ribalda@...omium.org>