linux-kernel - Re: [PATCH 1/4] media: i2c: imx214: Explain some magic numbers

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Message-ID: <169810104910.2245571.16606813523946813634@ping.linuxembedded.co.uk>
Date:   Mon, 23 Oct 2023 23:44:09 +0100
From:   Kieran Bingham <kieran.bingham@...asonboard.com>
To:     André Apitzsch <git@...tzsch.eu>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Ricardo Ribalda <ribalda@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht,
        André Apitzsch <git@...tzsch.eu>
Subject: Re: [PATCH 1/4] media: i2c: imx214: Explain some magic numbers

Quoting André Apitzsch (2023-10-23 22:47:50)
> Code refinement, no functional changes.
> 
> Signed-off-by: André Apitzsch <git@...tzsch.eu>
> ---
>  drivers/media/i2c/imx214.c | 24 +++++++++++++++++++-----
>  1 file changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/i2c/imx214.c b/drivers/media/i2c/imx214.c
> index 4f77ea02cc27..9218c149d4c8 100644
> --- a/drivers/media/i2c/imx214.c
> +++ b/drivers/media/i2c/imx214.c
> @@ -19,12 +19,23 @@
>  #include <media/v4l2-fwnode.h>
>  #include <media/v4l2-subdev.h>
>  
> +#define IMX214_REG_MODE_SELECT         0x0100
> +#define IMX214_MODE_STANDBY            0x00
> +#define IMX214_MODE_STREAMING          0x01
> +
>  #define IMX214_DEFAULT_CLK_FREQ        24000000
>  #define IMX214_DEFAULT_LINK_FREQ 480000000
>  #define IMX214_DEFAULT_PIXEL_RATE ((IMX214_DEFAULT_LINK_FREQ * 8LL) / 10)
>  #define IMX214_FPS 30
>  #define IMX214_MBUS_CODE MEDIA_BUS_FMT_SRGGB10_1X10
>  
> +/* Exposure control */
> +#define IMX214_REG_EXPOSURE            0x0202
> +#define IMX214_EXPOSURE_MIN            0
> +#define IMX214_EXPOSURE_MAX            3184
> +#define IMX214_EXPOSURE_STEP           1
> +#define IMX214_EXPOSURE_DEFAULT                0x0c70

I like this change, and I see that 0x0c70 was directly moved here from
the code below. But could we replace 0xc70 here with 3184 please so that
it's /far/ clearer that the Exposure Default == Exposure Max which is
otherwise hidden?

--
Regards

Kieran


> +
>  static const char * const imx214_supply_name[] = {
>         "vdda",
>         "vddd",
> @@ -665,7 +676,7 @@ static int imx214_set_ctrl(struct v4l2_ctrl *ctrl)
>         case V4L2_CID_EXPOSURE:
>                 vals[1] = ctrl->val;
>                 vals[0] = ctrl->val >> 8;
> -               ret = regmap_bulk_write(imx214->regmap, 0x202, vals, 2);
> +               ret = regmap_bulk_write(imx214->regmap, IMX214_REG_EXPOSURE, vals, 2);
>                 if (ret < 0)
>                         dev_err(imx214->dev, "Error %d\n", ret);
>                 ret = 0;
> @@ -743,7 +754,7 @@ static int imx214_start_streaming(struct imx214 *imx214)
>                 dev_err(imx214->dev, "could not sync v4l2 controls\n");
>                 goto error;
>         }
> -       ret = regmap_write(imx214->regmap, 0x100, 1);
> +       ret = regmap_write(imx214->regmap, IMX214_REG_MODE_SELECT, IMX214_MODE_STREAMING);
>         if (ret < 0) {
>                 dev_err(imx214->dev, "could not sent start table %d\n", ret);
>                 goto error;
> @@ -761,7 +772,7 @@ static int imx214_stop_streaming(struct imx214 *imx214)
>  {
>         int ret;
>  
> -       ret = regmap_write(imx214->regmap, 0x100, 0);
> +       ret = regmap_write(imx214->regmap, IMX214_REG_MODE_SELECT, IMX214_MODE_STANDBY);
>         if (ret < 0)
>                 dev_err(imx214->dev, "could not sent stop table %d\n",  ret);
>  
> @@ -991,9 +1002,12 @@ static int imx214_probe(struct i2c_client *client)
>          *
>          * Yours sincerely, Ricardo.
>          */
> -       imx214->exposure = v4l2_ctrl_new_std(&imx214->ctrls, &imx214_ctrl_ops,
> +       imx214->exposure = v4l2_ctrl_new_std(ctrl_hdlr, &imx214_ctrl_ops,
>                                              V4L2_CID_EXPOSURE,
> -                                            0, 3184, 1, 0x0c70);
> +                                            IMX214_EXPOSURE_MIN,
> +                                            IMX214_EXPOSURE_MAX,
> +                                            IMX214_EXPOSURE_STEP,
> +                                            IMX214_EXPOSURE_DEFAULT);
>  
>         imx214->unit_size = v4l2_ctrl_new_std_compound(&imx214->ctrls,
>                                 NULL,
> 
> -- 
> 2.42.0
>