linux-kernel - Re: [PATCH v1 2/2] media: i2c: imx219: Replace exposure magic value with named constant

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Message-ID: <CAPY8ntDAjyUF4gMO7a2HEcW8cnFaXe0bABtRA7bzWwrt1utp3Q@mail.gmail.com>
Date: Mon, 3 Nov 2025 18:19:04 +0000
From: Dave Stevenson <dave.stevenson@...pberrypi.com>
To: Tarang Raval <tarang.raval@...iconsignals.io>
Cc: sakari.ailus@...ux.intel.com, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] media: i2c: imx219: Replace exposure magic value
 with named constant

Hi Tarang

On Fri, 31 Oct 2025 at 11:49, Tarang Raval
<tarang.raval@...iconsignals.io> wrote:
>
> Introduce IMX219_EXPOSURE_OFFSET (4) and use it instead of the literal
> '4' when computing the maximum coarse exposure. The IMX219 datasheet
> specifies the maximum storage time as frame_length_lines - 4.
> (Ref: Datasheet section 5-7-1)
>
> Also fix one indentation issue for consistency.
>
> Signed-off-by: Tarang Raval <tarang.raval@...iconsignals.io>

Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>

> ---
>  drivers/media/i2c/imx219.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> index 40693635c0c3..e87d5a18fe87 100644
> --- a/drivers/media/i2c/imx219.c
> +++ b/drivers/media/i2c/imx219.c
> @@ -68,6 +68,7 @@
>  #define IMX219_EXPOSURE_STEP           1
>  #define IMX219_EXPOSURE_DEFAULT                0x640
>  #define IMX219_EXPOSURE_MAX            65535
> +#define IMX219_EXPOSURE_OFFSET                 4
>
>  /* V_TIMING internal */
>  #define IMX219_REG_FRM_LENGTH_A                CCI_REG16(0x0160)
> @@ -450,9 +451,9 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
>                 int exposure_max, exposure_def;
>
>                 /* Update max exposure while meeting expected vblanking */
> -               exposure_max = format->height + ctrl->val - 4;
> +               exposure_max = format->height + ctrl->val - IMX219_EXPOSURE_OFFSET;
>                 exposure_def = (exposure_max < IMX219_EXPOSURE_DEFAULT) ?
> -                       exposure_max : IMX219_EXPOSURE_DEFAULT;
> +                               exposure_max : IMX219_EXPOSURE_DEFAULT;
>                 ret = __v4l2_ctrl_modify_range(imx219->exposure,
>                                                imx219->exposure->minimum,
>                                                exposure_max,
> @@ -579,9 +580,9 @@ static int imx219_init_controls(struct imx219 *imx219)
>                                            IMX219_LLP_MIN - mode->width,
>                                            IMX219_LLP_MAX - mode->width, 1,
>                                            IMX219_LLP_MIN - mode->width);
> -       exposure_max = mode->fll_def - 4;
> +       exposure_max = mode->fll_def - IMX219_EXPOSURE_OFFSET;
>         exposure_def = (exposure_max < IMX219_EXPOSURE_DEFAULT) ?
> -               exposure_max : IMX219_EXPOSURE_DEFAULT;
> +                       exposure_max : IMX219_EXPOSURE_DEFAULT;
>         imx219->exposure = v4l2_ctrl_new_std(ctrl_hdlr, &imx219_ctrl_ops,
>                                              V4L2_CID_EXPOSURE,
>                                              IMX219_EXPOSURE_MIN, exposure_max,
> @@ -900,9 +901,9 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>                         return ret;
>
>                 /* Update max exposure while meeting expected vblanking */
> -               exposure_max = mode->fll_def - 4;
> +               exposure_max = mode->fll_def - IMX219_EXPOSURE_OFFSET;
>                 exposure_def = (exposure_max < IMX219_EXPOSURE_DEFAULT) ?
> -                       exposure_max : IMX219_EXPOSURE_DEFAULT;
> +                               exposure_max : IMX219_EXPOSURE_DEFAULT;
>                 ret = __v4l2_ctrl_modify_range(imx219->exposure,
>                                                imx219->exposure->minimum,
>                                                exposure_max,
> --
> 2.34.1
>