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

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Date:   Fri, 6 Jan 2023 10:45:23 +0100
From:   Jacopo Mondi <jacopo.mondi@...asonboard.com>
To:     shravan kumar <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

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

	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 ?


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