linux-kernel - Re: [PATCH v3 5/5] media: i2c: alvium: fix req_fr check into alvium_s_frame

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Date: Wed, 20 Dec 2023 14:52:53 +0100
From: Tommaso Merciai <tomm.merciai@...il.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linuxfancy@...glegroups.com, sakari.ailus@...ux.intel.com,
	martin.hecht@...et.eu, Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/5] media: i2c: alvium: fix req_fr check into
 alvium_s_frame_interval()

Hi Laurent,

On Wed, Dec 20, 2023 at 03:02:36PM +0200, Laurent Pinchart wrote:
> Hi Tommaso,
> 
> Thank you for the patch.
> 
> On Wed, Dec 20, 2023 at 01:40:23PM +0100, Tommaso Merciai wrote:
> > Actually req_fr check into alvium_s_frame_interval() is wrong.
> > In particular req_fr can't be >=max and <= min at the same time.
> > Fix this using clamp and remove dft_fr parameter from
> > alvium_get_frame_interval() not more used.
> 
> The commit message should have explained why clamping is better than
> picking a default value, as that's a functional change. If you propose
> an updated commit message in a reply, I think Sakari can update the
> patch when applying the series to his tree, there's no need for a v4.

What about:

Actually req_fr check into alvium_s_frame_interval() is wrong.
In particular req_fr can't be >=max and <= min at the same time.
Fix this using clamp and remove dft_fr parameter from
alvium_get_frame_interval() not more used.

Clamp function make sure that if the setted value exceeds the limits is
replaced with min_fr/max_fr instead of setting the value readed back
from the hw.

What do you think?

Thanks & Regards,
Tommaso

> 
> > Signed-off-by: Tommaso Merciai <tomm.merciai@...il.com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> > ---
> >  drivers/media/i2c/alvium-csi2.c | 12 ++++--------
> >  1 file changed, 4 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/media/i2c/alvium-csi2.c b/drivers/media/i2c/alvium-csi2.c
> > index 240bf991105e..01111a00902d 100644
> > --- a/drivers/media/i2c/alvium-csi2.c
> > +++ b/drivers/media/i2c/alvium-csi2.c
> > @@ -1171,12 +1171,10 @@ static int alvium_set_bayer_pattern(struct alvium_dev *alvium,
> >  }
> >  
> >  static int alvium_get_frame_interval(struct alvium_dev *alvium,
> > -				     u64 *dft_fr, u64 *min_fr, u64 *max_fr)
> > +				     u64 *min_fr, u64 *max_fr)
> >  {
> >  	int ret = 0;
> >  
> > -	alvium_read(alvium, REG_BCRM_ACQUISITION_FRAME_RATE_RW,
> > -		    dft_fr, &ret);
> >  	alvium_read(alvium, REG_BCRM_ACQUISITION_FRAME_RATE_MIN_R,
> >  		    min_fr, &ret);
> >  	alvium_read(alvium, REG_BCRM_ACQUISITION_FRAME_RATE_MAX_R,
> > @@ -1647,7 +1645,7 @@ static int alvium_s_frame_interval(struct v4l2_subdev *sd,
> >  {
> >  	struct alvium_dev *alvium = sd_to_alvium(sd);
> >  	struct device *dev = &alvium->i2c_client->dev;
> > -	u64 req_fr, dft_fr, min_fr, max_fr;
> > +	u64 req_fr, min_fr, max_fr;
> >  	struct v4l2_fract *interval;
> >  	int ret;
> >  
> > @@ -1657,7 +1655,7 @@ static int alvium_s_frame_interval(struct v4l2_subdev *sd,
> >  	if (fi->interval.denominator == 0)
> >  		return -EINVAL;
> >  
> > -	ret = alvium_get_frame_interval(alvium, &dft_fr, &min_fr, &max_fr);
> > +	ret = alvium_get_frame_interval(alvium, &min_fr, &max_fr);
> >  	if (ret) {
> >  		dev_err(dev, "Fail to get frame interval\n");
> >  		return ret;
> > @@ -1670,9 +1668,7 @@ static int alvium_s_frame_interval(struct v4l2_subdev *sd,
> >  
> >  	req_fr = (u64)((fi->interval.denominator * USEC_PER_SEC) /
> >  		       fi->interval.numerator);
> > -
> > -	if (req_fr >= max_fr && req_fr <= min_fr)
> > -		req_fr = dft_fr;
> > +	req_fr = clamp(req_fr, min_fr, max_fr);
> >  
> >  	interval = v4l2_subdev_state_get_interval(sd_state, 0);
> >  
> 
> -- 
> Regards,
> 
> Laurent Pinchart