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From:   Dave Stevenson <dave.stevenson@raspberrypi.com>
Date:   Fri, 28 Feb 2020 13:44:37 +0000
Message-ID: <CAPY8ntB17QjCSyefwTrMhudwkiFYT_5x3i1=KjzFv+p6tbrQEA@mail.gmail.com>
Subject: Re: [PATCH] media: i2c: imx219: add support for enum frame interval
To:     Eugen Hristev <eugen.hristev@microchip.com>
Cc:     Andrey Konovalov <andrey.konovalov@linaro.org>,
        Sakari Ailus <sakari.ailus@iki.fi>,
        Linux Media Mailing List <linux-media@vger.kernel.org>,
        linux-kernel@vger.kernel.org
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Hi Eugen.

On Thu, 27 Feb 2020 at 15:19, Eugen Hristev <eugen.hristev@microchip.com> wrote:
>
> Add support for enum frame intervals IOCTL.
> The current supported framerates are only available as comments inside
> the code.
> Add support for VIDIOC_ENUM_FRAMEINTERVALS as the enum_frame_interval
> callback as pad ops.
>
>  # v4l2-ctl --list-frameintervals width=1920,height=1080,pixelformat=RG10
>  ioctl: VIDIOC_ENUM_FRAMEINTERVALS
>         Interval: Discrete 0.067s (15.000 fps)
>         Interval: Discrete 0.033s (30.000 fps)
>         Interval: Discrete 0.033s (30.000 fps)

But the frame rates are not discrete. You have frame rate control via
V4L2_CID_VBLANK, which can be used in conjunction with V4L2_CID_HBLANK
and V4L2_CID_PIXEL_RATE to determine actual frame period.

See https://linuxtv.org/downloads/v4l-dvb-apis-new/uapi/v4l/ext-ctrls-image-source.html?highlight=v4l2_cid_vblank
I believe this is the preferred route to doing frame rate control on
image sensors. I assume someone will correct me if I'm wrong on that.

  Dave

> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> ---
>
> Hello,
>
> This is on top of Sakari's tree in linuxtv.org
>
> Thanks
> Eugen
>
>  drivers/media/i2c/imx219.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> index f1effb5a5f66..17fcedd4edb6 100644
> --- a/drivers/media/i2c/imx219.c
> +++ b/drivers/media/i2c/imx219.c
> @@ -127,6 +127,8 @@ struct imx219_mode {
>         unsigned int width;
>         /* Frame height */
>         unsigned int height;
> +       /* Frame rate */
> +       u8 fps;
>
>         /* V-timing */
>         unsigned int vts_def;
> @@ -381,6 +383,7 @@ static const struct imx219_mode supported_modes[] = {
>                 /* 8MPix 15fps mode */
>                 .width = 3280,
>                 .height = 2464,
> +               .fps = 15,
>                 .vts_def = IMX219_VTS_15FPS,
>                 .reg_list = {
>                         .num_of_regs = ARRAY_SIZE(mode_3280x2464_regs),
> @@ -391,6 +394,7 @@ static const struct imx219_mode supported_modes[] = {
>                 /* 1080P 30fps cropped */
>                 .width = 1920,
>                 .height = 1080,
> +               .fps = 30,
>                 .vts_def = IMX219_VTS_30FPS_1080P,
>                 .reg_list = {
>                         .num_of_regs = ARRAY_SIZE(mode_1920_1080_regs),
> @@ -401,6 +405,7 @@ static const struct imx219_mode supported_modes[] = {
>                 /* 2x2 binned 30fps mode */
>                 .width = 1640,
>                 .height = 1232,
> +               .fps = 30,
>                 .vts_def = IMX219_VTS_30FPS_BINNED,
>                 .reg_list = {
>                         .num_of_regs = ARRAY_SIZE(mode_1640_1232_regs),
> @@ -680,6 +685,27 @@ static int imx219_enum_frame_size(struct v4l2_subdev *sd,
>         return 0;
>  }
>
> +static int imx219_enum_frame_interval(struct v4l2_subdev *sd,
> +                                     struct v4l2_subdev_pad_config *cfg,
> +                                     struct v4l2_subdev_frame_interval_enum *fie)
> +{
> +       struct imx219 *imx219 = to_imx219(sd);
> +
> +       if (fie->index >= ARRAY_SIZE(supported_modes))
> +               return -EINVAL;
> +
> +       if (fie->code != imx219_get_format_code(imx219))
> +               return -EINVAL;
> +
> +       if (fie->pad)
> +               return -EINVAL;
> +
> +       fie->interval.numerator = 1;
> +       fie->interval.denominator = supported_modes[fie->index].fps;
> +
> +       return 0;
> +}
> +
>  static void imx219_reset_colorspace(struct v4l2_mbus_framefmt *fmt)
>  {
>         fmt->colorspace = V4L2_COLORSPACE_SRGB;
> @@ -1004,6 +1030,7 @@ static const struct v4l2_subdev_pad_ops imx219_pad_ops = {
>         .get_fmt = imx219_get_pad_format,
>         .set_fmt = imx219_set_pad_format,
>         .enum_frame_size = imx219_enum_frame_size,
> +       .enum_frame_interval = imx219_enum_frame_interval,
>  };
>
>  static const struct v4l2_subdev_ops imx219_subdev_ops = {
> --
> 2.20.1
>