linux-kernel - RE: [PATCH v8 1/4] media: i2c: imx334: replace __v4l2_ctrl_s_ctrl to __v4l2_ctrl_modify

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Message-ID: <PH0PR11MB56110B87E3C7C6109E5310D681FB9@PH0PR11MB5611.namprd11.prod.outlook.com>
Date:   Fri, 6 Jan 2023 11:58:30 +0000
From:   <Shravan.Chippa@...rochip.com>
To:     <jacopo.mondi@...asonboard.com>, <hverkuil@...all.nl>
CC:     <paul.j.murphy@...el.com>, <daniele.alessandrelli@...el.com>,
        <mchehab@...nel.org>, <linux-media@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v8 1/4] media: i2c: imx334: replace __v4l2_ctrl_s_ctrl to
 __v4l2_ctrl_modify_range



> -----Original Message-----
> From: Jacopo Mondi <jacopo.mondi@...asonboard.com>
> Sent: 06 January 2023 03:15 PM
> To: shravan Chippa - I35088 <Shravan.Chippa@...rochip.com>; Hans Verkuil
> <hverkuil@...all.nl>
> Cc: paul.j.murphy@...el.com; daniele.alessandrelli@...el.com;
> mchehab@...nel.org; linux-media@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH v8 1/4] media: i2c: imx334: replace __v4l2_ctrl_s_ctrl to
> __v4l2_ctrl_modify_range
> 
> [You don't often get email from jacopo.mondi@...asonboard.com. Learn
> why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the
> content is safe
> 
> Hi Sharavan,
> 
> I'm a bit confused here
> 
> On Fri, Jan 06, 2023 at 12:59:28PM +0530, shravan kumar wrote:
> > From: Shravan Chippa <shravan.chippa@...rochip.com>
> >
> > For evry mode we will get new set of values for hbalnk so use
> > __v4l2_ctrl_modify_range() to support multi modes for hblank.
> >
> > The hblank value is readonly in the driver. because of this the
> > function returns error if we try to change. so added dumy return case
> > in imx334_set_ctrl function
> >
> > Suggested-by: Jacopo Mondi <jacopo@...ndi.org>
> > Signed-off-by: Shravan Chippa <shravan.chippa@...rochip.com>
> > ---
> >  drivers/media/i2c/imx334.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/i2c/imx334.c b/drivers/media/i2c/imx334.c
> > index 7b0a9086447d..ebacba3059b3 100644
> > --- a/drivers/media/i2c/imx334.c
> > +++ b/drivers/media/i2c/imx334.c
> > @@ -382,7 +382,8 @@ static int imx334_update_controls(struct imx334
> *imx334,
> >       if (ret)
> >               return ret;
> >
> > -     ret = __v4l2_ctrl_s_ctrl(imx334->hblank_ctrl, mode->hblank);
> > +     ret = __v4l2_ctrl_modify_range(imx334->hblank_ctrl, mode->hblank,
> > +                                    mode->hblank, 1, mode->hblank);
> >       if (ret)
> >               return ret;
> >
> > @@ -480,6 +481,9 @@ static int imx334_set_ctrl(struct v4l2_ctrl *ctrl)
> >
> >               pm_runtime_put(imx334->dev);
> >
> > +             break;
> > +     case V4L2_CID_HBLANK:
> > +             ret = 0;
> 
> Hblank is said to be read-only

Yes, read-only.
> 
>         if (imx334->hblank_ctrl)
>                 imx334->hblank_ctrl->flags |= V4L2_CTRL_FLAG_READ_ONLY;
> 
> So you shouldn't need this safety measure here.
> 
> However I see that __v4l2_ctrl_modify_range() can call s_ctrl() if the current
> value has to be adjusted to the new limits.
> 
> Hans, how does this work ? Do we need the above even if the control is said
> to be RO ?
> 
> Sharavan: have you experienced failures here, or is this just for safety ?

The value is changing if we change the mode. 
While changing mode. I have experienced failures.

Thanks,
Shravan.

> 
> 
> >               break;
> >       default:
> >               dev_err(imx334->dev, "Invalid control %d", ctrl->id);
> > --
> > 2.34.1
> >