linux-kernel - [PATCH 3/3] media: iris: Fix fps calculation

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Message-Id: <20251203-warnings-6-19-v1-3-25308e136bca@chromium.org>
Date: Wed, 03 Dec 2025 08:55:36 +0000
From: Ricardo Ribalda <ribalda@...omium.org>
To: Keke Li <keke.li@...ogic.com>, 
 Jacopo Mondi <jacopo.mondi@...asonboard.com>, 
 Daniel Scally <dan.scally@...asonboard.com>, 
 Hans Verkuil <hverkuil+cisco@...nel.org>, 
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, 
 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>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>
Subject: [PATCH 3/3] 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")
Reviewed-by: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
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 5830eba93c68b27fa9db87bac63a691eaca338d2..730f2aa1a83b2f4f90227ab9a7e04aee7c2c3cfe 100644
--- a/drivers/media/platform/qcom/iris/iris_venc.c
+++ b/drivers/media/platform/qcom/iris/iris_venc.c
@@ -408,11 +408,10 @@ 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;

-- 
2.52.0.158.g65b55ccf14-goog