Re: [PATCH v4 05/29] media: imx219: Fix vertical blanking and exposure for analogue binning

[Jacopo Mondi <jacopo.mondi@ideasonboard.com>]

Hi Sakari

On Wed, Apr 08, 2026 at 06:39:14PM +0300, Sakari Ailus wrote:
> When vertical analogue binning is in use, the minimum frame length in
> lines decreases to around half of the normal. In relation to the sensor's
> output size this means vertical blanking can be negative but that's not an
> issue as control values are signed. Remove the workaround for this
> non-issue that doubled the pixel rate, frame length in lines and exposure
> time.

I don't think this was a workaround. Doubling the pixel rate and
halving the values written to registers for EXPOSURE and VBLANK
allowed userspace to maintain a consistent view while the driver
accounts for the special binning mode where, at least in my latest
understanding, the sensor averages two lines before passing them to
the ADC.

I am missing in which case, with the current driver implementation,
the vertical blanking can be negative.

>
> The resulting change also fixes the minimum, the maximum and the step
> values for the control.
>
> Fixes: f513997119f4 ("media: i2c: imx219: Scale the pixel rate for analog binning")
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

Jai, and others including Dave and me, have spent quite some time
testing and implementing proper support for the special analogue
binning mode for this sensor. Of course we might have missed something
obvious, but I'm still missing what you're trying to fix here.

> ---
>  drivers/media/i2c/imx219.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> index 6819a2fa3262..a72630ad1561 100644
> --- a/drivers/media/i2c/imx219.c
> +++ b/drivers/media/i2c/imx219.c
> @@ -420,15 +420,6 @@ static void imx219_get_binning(struct v4l2_subdev_state *state, u8 *bin_h,
>
>  }
>
> -static inline u32 imx219_get_rate_factor(struct v4l2_subdev_state *state)
> -{
> -	u8 bin_h, bin_v;
> -
> -	imx219_get_binning(state, &bin_h, &bin_v);
> -
> -	return (bin_h & bin_v) == IMX219_BINNING_X2_ANALOG ? 2 : 1;
> -}
> -
>  /* -----------------------------------------------------------------------------
>   * Controls
>   */
> @@ -440,12 +431,10 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
>  	struct i2c_client *client = v4l2_get_subdevdata(&imx219->sd);
>  	const struct v4l2_mbus_framefmt *format;
>  	struct v4l2_subdev_state *state;
> -	u32 rate_factor;
>  	int ret = 0;
>
>  	state = v4l2_subdev_get_locked_active_state(&imx219->sd);
>  	format = v4l2_subdev_state_get_format(state, 0);
> -	rate_factor = imx219_get_rate_factor(state);
>
>  	if (ctrl->id == V4L2_CID_VBLANK) {
>  		int exposure_max, exposure_def;
> @@ -478,7 +467,7 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
>  		break;
>  	case V4L2_CID_EXPOSURE:
>  		cci_write(imx219->regmap, IMX219_REG_EXPOSURE,
> -			  ctrl->val / rate_factor, &ret);
> +			  ctrl->val, &ret);
>  		break;
>  	case V4L2_CID_DIGITAL_GAIN:
>  		cci_write(imx219->regmap, IMX219_REG_DIGITAL_GAIN,
> @@ -495,7 +484,7 @@ static int imx219_set_ctrl(struct v4l2_ctrl *ctrl)
>  		break;
>  	case V4L2_CID_VBLANK:
>  		cci_write(imx219->regmap, IMX219_REG_FRM_LENGTH_A,
> -			  (format->height + ctrl->val) / rate_factor, &ret);
> +			  format->height + ctrl->val, &ret);
>  		break;
>  	case V4L2_CID_HBLANK:
>  		cci_write(imx219->regmap, IMX219_REG_LINE_LENGTH_A,
> @@ -878,7 +867,6 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  	crop->top = (IMX219_NATIVE_HEIGHT - crop->height) / 2;
>
>  	if (fmt->which == V4L2_SUBDEV_FORMAT_ACTIVE) {
> -		unsigned int rate_factor = imx219_get_rate_factor(state);
>  		int exposure_max;
>  		int exposure_def;
>  		int llp_min;
> @@ -886,15 +874,16 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>
>  		/* Update limits and set FPS to default */
>  		ret = __v4l2_ctrl_modify_range(imx219->vblank,
> -					       IMX219_VBLANK_MIN * rate_factor,
> -					       (IMX219_FLL_MAX - mode->height) *
> -					       rate_factor, rate_factor,
> -					       mode->fll_def - mode->height);
> +					       (int)(mode->height / binning),
> +					       IMX219_FLL_MAX - mode->height, 1,
> +					       (int)(mode->fll_def / binning) -
> +					       (int)mode->height);
>  		if (ret)
>  			return ret;
>
>  		ret = __v4l2_ctrl_s_ctrl(imx219->vblank,
> -					 mode->fll_def - mode->height);
> +					 (int)(mode->fll_def / binning) -
> +					 (int)mode->height);
>  		if (ret)
>  			return ret;
>
> @@ -931,7 +920,7 @@ static int imx219_set_pad_format(struct v4l2_subdev *sd,
>  			return ret;
>
>  		/* Scale the pixel rate based on the mode specific factor */
> -		pixel_rate = imx219_get_pixel_rate(imx219) * rate_factor;
> +		pixel_rate = imx219_get_pixel_rate(imx219);
>  		ret = __v4l2_ctrl_modify_range(imx219->pixel_rate, pixel_rate,
>  					       pixel_rate, 1, pixel_rate);
>  		if (ret)
> --
> 2.47.3
>
>