[3/3] media: i2c: ov9282: add strobe_timeout v4l2 control

Commit Message

Richard Leitner March 3, 2025, 10:58 p.m. UTC

Add V4L2_CID_FLASH_TIMEOUT support using the "strobe_frame_span"
feature of the sensor. This is implemented by transforming the given µs
value by an interpolated formula to a "span step width" value and
writing it to register PWM_CTRL_25, PWM_CTRL_26, PWM_CTRL_27,
PWM_CTRL_28 (0x3925, 0x3926, 0x3927, 0x3928).

The maximum control value is set to the period of the current framerate.
This must be changed to a dynamic range as soon as this driver
implements the set_frame_interval() pad operation.

All register values are based on the OV9281 datasheet v1.53 (jan 2019)
and tested using an ov9281 VisionComponents module.

Signed-off-by: Richard Leitner <[e-mail]>
---
 drivers/media/i2c/ov9282.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

Comments

Dave Stevenson March 4, 2025, 10:28 a.m. UTC | #1

Hi Richard

On Mon, 3 Mar 2025 at 22:59, Richard Leitner <[e-mail]> wrote:
>
> Add V4L2_CID_FLASH_TIMEOUT support using the "strobe_frame_span"
> feature of the sensor. This is implemented by transforming the given µs
> value by an interpolated formula to a "span step width" value and
> writing it to register PWM_CTRL_25, PWM_CTRL_26, PWM_CTRL_27,
> PWM_CTRL_28 (0x3925, 0x3926, 0x3927, 0x3928).
>
> The maximum control value is set to the period of the current framerate.
> This must be changed to a dynamic range as soon as this driver
> implements the set_frame_interval() pad operation.
>
> All register values are based on the OV9281 datasheet v1.53 (jan 2019)
> and tested using an ov9281 VisionComponents module.
>
> Signed-off-by: Richard Leitner <[e-mail]>
> ---
>  drivers/media/i2c/ov9282.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> index c98ba466e9aea29baff0b13578d760bf69c958c5..f7dfe8987e524b73af7e16e12567e96627b4f89a 100644
> --- a/drivers/media/i2c/ov9282.c
> +++ b/drivers/media/i2c/ov9282.c
> @@ -97,6 +97,10 @@
>  #define OV9282_REG_MIPI_CTRL00 0x4800
>  #define OV9282_GATED_CLOCK     BIT(5)
>
> +/* Flash/Strobe control registers */
> +#define OV9282_REG_FLASH_DURATION      0x3925
> +#define OV9282_FLASH_DURATION_DEFAULT  0x0000001A
> +
>  /* Input clock rate */
>  #define OV9282_INCLK_RATE      24000000
>
> @@ -193,6 +197,7 @@ struct ov9282_mode {
>   * @again_ctrl: Pointer to analog gain control
>   * @pixel_rate: Pointer to pixel rate control
>   * @flash_led_mode: Pointer to flash led mode control
> + * @flash_timeout: Pointer to flash timeout control
>   * @vblank: Vertical blanking in lines
>   * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
>   * @cur_mode: Pointer to current selected sensor mode
> @@ -216,6 +221,7 @@ struct ov9282 {
>         };
>         struct v4l2_ctrl *pixel_rate;
>         struct v4l2_ctrl *flash_led_mode;
> +       struct v4l2_ctrl *flash_timeout;

You only access this in ov9282_set_ctrl where you already have the
struct v4l2_ctrl, so there is no need to store this in the main device
state.

  Dave

>         u32 vblank;
>         bool noncontinuous_clock;
>         const struct ov9282_mode *cur_mode;
> @@ -689,6 +695,24 @@ static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
>                                 current_val);
>  }
>
> +static int ov9282_set_ctrl_flash_timeout(struct ov9282 *ov9282, int value)
> +{
> +       /* Calculate "strobe_frame_span" increments from a given value (µs).
> +        * This is quite tricky as "The step width of shift and span is
> +        * programmable under system clock domain.", but it's not documented
> +        * how to program this step width (at least in the datasheet available
> +        * to the author at time of writing).
> +        * The formula below is interpolated from different modes/framerates
> +        * and should work quite well for most settings.
> +        */
> +       u32 val = value * 192 / (ov9282->cur_mode->width + ov9282->hblank_ctrl->val);
> +
> +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION, 1, (val >> 24) & 0xff);
> +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 1, 1, (val >> 16) & 0xff);
> +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 2, 1, (val >> 8) & 0xff);
> +       return ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 3, 1, val & 0xff);
> +}
> +
>  /**
>   * ov9282_set_ctrl() - Set subdevice control
>   * @ctrl: pointer to v4l2_ctrl structure
> @@ -758,6 +782,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
>         case V4L2_CID_FLASH_LED_MODE:
>                 ret = ov9282_set_ctrl_flash_led_mode(ov9282, ctrl->val);
>                 break;
> +       case V4L2_CID_FLASH_TIMEOUT:
> +               ret = ov9282_set_ctrl_flash_timeout(ov9282, ctrl->val);
> +               break;
>         default:
>                 dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
>                 ret = -EINVAL;
> @@ -1420,6 +1447,10 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
>                                                         (1 << V4L2_FLASH_LED_MODE_TORCH),
>                                                         V4L2_FLASH_LED_MODE_NONE);
>
> +       ov9282->flash_timeout = v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
> +                                                 V4L2_CID_FLASH_TIMEOUT,
> +                                                 0, 13900, 1, 8);
> +
>         ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
>         if (!ret) {
>                 /* Failure sets ctrl_hdlr->error, which we check afterwards anyway */
>
> --
> 2.47.2
>
>

Dave Stevenson March 4, 2025, 5:30 p.m. UTC | #2

On Tue, 4 Mar 2025 at 10:28, Dave Stevenson
<[e-mail]> wrote:
>
> Hi Richard
>
> On Mon, 3 Mar 2025 at 22:59, Richard Leitner <[e-mail]> wrote:
> >
> > Add V4L2_CID_FLASH_TIMEOUT support using the "strobe_frame_span"
> > feature of the sensor. This is implemented by transforming the given µs
> > value by an interpolated formula to a "span step width" value and
> > writing it to register PWM_CTRL_25, PWM_CTRL_26, PWM_CTRL_27,
> > PWM_CTRL_28 (0x3925, 0x3926, 0x3927, 0x3928).
> >
> > The maximum control value is set to the period of the current framerate.
> > This must be changed to a dynamic range as soon as this driver
> > implements the set_frame_interval() pad operation.

Rereading the patch as I'm looking at the whole series.

set_frame_interval() will never be implemented as it is the wrong API
for raw sensors.
See https://www.kernel.org/doc/html/latest/userspace-api/media/drivers/camera-sensor.html#raw-camera-sensors
This driver already implements PIXEL_RATE, HBLANK, and VBLANK for
frame interval configuration.

> >
> > All register values are based on the OV9281 datasheet v1.53 (jan 2019)
> > and tested using an ov9281 VisionComponents module.
> >
> > Signed-off-by: Richard Leitner <[e-mail]>
> > ---
> >  drivers/media/i2c/ov9282.c | 31 +++++++++++++++++++++++++++++++
> >  1 file changed, 31 insertions(+)
> >
> > diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> > index c98ba466e9aea29baff0b13578d760bf69c958c5..f7dfe8987e524b73af7e16e12567e96627b4f89a 100644
> > --- a/drivers/media/i2c/ov9282.c
> > +++ b/drivers/media/i2c/ov9282.c
> > @@ -97,6 +97,10 @@
> >  #define OV9282_REG_MIPI_CTRL00 0x4800
> >  #define OV9282_GATED_CLOCK     BIT(5)
> >
> > +/* Flash/Strobe control registers */
> > +#define OV9282_REG_FLASH_DURATION      0x3925
> > +#define OV9282_FLASH_DURATION_DEFAULT  0x0000001A
> > +
> >  /* Input clock rate */
> >  #define OV9282_INCLK_RATE      24000000
> >
> > @@ -193,6 +197,7 @@ struct ov9282_mode {
> >   * @again_ctrl: Pointer to analog gain control
> >   * @pixel_rate: Pointer to pixel rate control
> >   * @flash_led_mode: Pointer to flash led mode control
> > + * @flash_timeout: Pointer to flash timeout control
> >   * @vblank: Vertical blanking in lines
> >   * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
> >   * @cur_mode: Pointer to current selected sensor mode
> > @@ -216,6 +221,7 @@ struct ov9282 {
> >         };
> >         struct v4l2_ctrl *pixel_rate;
> >         struct v4l2_ctrl *flash_led_mode;
> > +       struct v4l2_ctrl *flash_timeout;
>
> You only access this in ov9282_set_ctrl where you already have the
> struct v4l2_ctrl, so there is no need to store this in the main device
> state.
>
>   Dave
>
> >         u32 vblank;
> >         bool noncontinuous_clock;
> >         const struct ov9282_mode *cur_mode;
> > @@ -689,6 +695,24 @@ static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
> >                                 current_val);
> >  }
> >
> > +static int ov9282_set_ctrl_flash_timeout(struct ov9282 *ov9282, int value)
> > +{
> > +       /* Calculate "strobe_frame_span" increments from a given value (µs).
> > +        * This is quite tricky as "The step width of shift and span is
> > +        * programmable under system clock domain.", but it's not documented
> > +        * how to program this step width (at least in the datasheet available
> > +        * to the author at time of writing).
> > +        * The formula below is interpolated from different modes/framerates
> > +        * and should work quite well for most settings.
> > +        */
> > +       u32 val = value * 192 / (ov9282->cur_mode->width + ov9282->hblank_ctrl->val);
> > +
> > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION, 1, (val >> 24) & 0xff);
> > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 1, 1, (val >> 16) & 0xff);
> > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 2, 1, (val >> 8) & 0xff);
> > +       return ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 3, 1, val & 0xff);
> > +}
> > +
> >  /**
> >   * ov9282_set_ctrl() - Set subdevice control
> >   * @ctrl: pointer to v4l2_ctrl structure
> > @@ -758,6 +782,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
> >         case V4L2_CID_FLASH_LED_MODE:
> >                 ret = ov9282_set_ctrl_flash_led_mode(ov9282, ctrl->val);
> >                 break;
> > +       case V4L2_CID_FLASH_TIMEOUT:
> > +               ret = ov9282_set_ctrl_flash_timeout(ov9282, ctrl->val);
> > +               break;
> >         default:
> >                 dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
> >                 ret = -EINVAL;
> > @@ -1420,6 +1447,10 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
> >                                                         (1 << V4L2_FLASH_LED_MODE_TORCH),
> >                                                         V4L2_FLASH_LED_MODE_NONE);
> >
> > +       ov9282->flash_timeout = v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
> > +                                                 V4L2_CID_FLASH_TIMEOUT,
> > +                                                 0, 13900, 1, 8);
> > +
> >         ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
> >         if (!ret) {
> >                 /* Failure sets ctrl_hdlr->error, which we check afterwards anyway */
> >
> > --
> > 2.47.2
> >
> >

Richard Leitner March 5, 2025, 6:29 a.m. UTC | #3

On Tue, Mar 04, 2025 at 10:28:45AM +0000, Dave Stevenson wrote:
> Hi Richard
> 
> On Mon, 3 Mar 2025 at 22:59, Richard Leitner <[e-mail]> wrote:
> >
> > Add V4L2_CID_FLASH_TIMEOUT support using the "strobe_frame_span"
> > feature of the sensor. This is implemented by transforming the given µs
> > value by an interpolated formula to a "span step width" value and
> > writing it to register PWM_CTRL_25, PWM_CTRL_26, PWM_CTRL_27,
> > PWM_CTRL_28 (0x3925, 0x3926, 0x3927, 0x3928).
> >
> > The maximum control value is set to the period of the current framerate.
> > This must be changed to a dynamic range as soon as this driver
> > implements the set_frame_interval() pad operation.
> >
> > All register values are based on the OV9281 datasheet v1.53 (jan 2019)
> > and tested using an ov9281 VisionComponents module.
> >
> > Signed-off-by: Richard Leitner <[e-mail]>
> > ---
> >  drivers/media/i2c/ov9282.c | 31 +++++++++++++++++++++++++++++++
> >  1 file changed, 31 insertions(+)
> >
> > diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> > index c98ba466e9aea29baff0b13578d760bf69c958c5..f7dfe8987e524b73af7e16e12567e96627b4f89a 100644
> > --- a/drivers/media/i2c/ov9282.c
> > +++ b/drivers/media/i2c/ov9282.c
> > @@ -97,6 +97,10 @@
> >  #define OV9282_REG_MIPI_CTRL00 0x4800
> >  #define OV9282_GATED_CLOCK     BIT(5)
> >
> > +/* Flash/Strobe control registers */
> > +#define OV9282_REG_FLASH_DURATION      0x3925
> > +#define OV9282_FLASH_DURATION_DEFAULT  0x0000001A
> > +
> >  /* Input clock rate */
> >  #define OV9282_INCLK_RATE      24000000
> >
> > @@ -193,6 +197,7 @@ struct ov9282_mode {
> >   * @again_ctrl: Pointer to analog gain control
> >   * @pixel_rate: Pointer to pixel rate control
> >   * @flash_led_mode: Pointer to flash led mode control
> > + * @flash_timeout: Pointer to flash timeout control
> >   * @vblank: Vertical blanking in lines
> >   * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
> >   * @cur_mode: Pointer to current selected sensor mode
> > @@ -216,6 +221,7 @@ struct ov9282 {
> >         };
> >         struct v4l2_ctrl *pixel_rate;
> >         struct v4l2_ctrl *flash_led_mode;
> > +       struct v4l2_ctrl *flash_timeout;
> 
> You only access this in ov9282_set_ctrl where you already have the
> struct v4l2_ctrl, so there is no need to store this in the main device
> state.

Sure. Thanks for reviewing and pointing this out. Will fix that in v2.

(At least I was consistent and made the same mistakes for both controls ;-))

regards;rl

> 
>   Dave
> 
> >         u32 vblank;
> >         bool noncontinuous_clock;
> >         const struct ov9282_mode *cur_mode;
> > @@ -689,6 +695,24 @@ static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
> >                                 current_val);
> >  }
> >
> > +static int ov9282_set_ctrl_flash_timeout(struct ov9282 *ov9282, int value)
> > +{
> > +       /* Calculate "strobe_frame_span" increments from a given value (µs).
> > +        * This is quite tricky as "The step width of shift and span is
> > +        * programmable under system clock domain.", but it's not documented
> > +        * how to program this step width (at least in the datasheet available
> > +        * to the author at time of writing).
> > +        * The formula below is interpolated from different modes/framerates
> > +        * and should work quite well for most settings.
> > +        */
> > +       u32 val = value * 192 / (ov9282->cur_mode->width + ov9282->hblank_ctrl->val);
> > +
> > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION, 1, (val >> 24) & 0xff);
> > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 1, 1, (val >> 16) & 0xff);
> > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 2, 1, (val >> 8) & 0xff);
> > +       return ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 3, 1, val & 0xff);
> > +}
> > +
> >  /**
> >   * ov9282_set_ctrl() - Set subdevice control
> >   * @ctrl: pointer to v4l2_ctrl structure
> > @@ -758,6 +782,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
> >         case V4L2_CID_FLASH_LED_MODE:
> >                 ret = ov9282_set_ctrl_flash_led_mode(ov9282, ctrl->val);
> >                 break;
> > +       case V4L2_CID_FLASH_TIMEOUT:
> > +               ret = ov9282_set_ctrl_flash_timeout(ov9282, ctrl->val);
> > +               break;
> >         default:
> >                 dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
> >                 ret = -EINVAL;
> > @@ -1420,6 +1447,10 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
> >                                                         (1 << V4L2_FLASH_LED_MODE_TORCH),
> >                                                         V4L2_FLASH_LED_MODE_NONE);
> >
> > +       ov9282->flash_timeout = v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
> > +                                                 V4L2_CID_FLASH_TIMEOUT,
> > +                                                 0, 13900, 1, 8);
> > +
> >         ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
> >         if (!ret) {
> >                 /* Failure sets ctrl_hdlr->error, which we check afterwards anyway */
> >
> > --
> > 2.47.2
> >
> >

Richard Leitner March 5, 2025, 6:36 a.m. UTC | #4

Hi Dave,

On Tue, Mar 04, 2025 at 05:30:13PM +0000, Dave Stevenson wrote:
> On Tue, 4 Mar 2025 at 10:28, Dave Stevenson
> <[e-mail]> wrote:
> >
> > Hi Richard
> >
> > On Mon, 3 Mar 2025 at 22:59, Richard Leitner <[e-mail]> wrote:
> > >
> > > Add V4L2_CID_FLASH_TIMEOUT support using the "strobe_frame_span"
> > > feature of the sensor. This is implemented by transforming the given µs
> > > value by an interpolated formula to a "span step width" value and
> > > writing it to register PWM_CTRL_25, PWM_CTRL_26, PWM_CTRL_27,
> > > PWM_CTRL_28 (0x3925, 0x3926, 0x3927, 0x3928).
> > >
> > > The maximum control value is set to the period of the current framerate.
> > > This must be changed to a dynamic range as soon as this driver
> > > implements the set_frame_interval() pad operation.
> 
> Rereading the patch as I'm looking at the whole series.
> 
> set_frame_interval() will never be implemented as it is the wrong API
> for raw sensors.
> See https://www.kernel.org/doc/html/latest/userspace-api/media/drivers/camera-sensor.html#raw-camera-sensors
> This driver already implements PIXEL_RATE, HBLANK, and VBLANK for
> frame interval configuration.

Thanks Dave for bringing this up and sorry for not having known that
before posting this series. It's my first work on camera sensors/v4l2
and altough I have read a ton of docs I somehow missed this one.

So regarding this patch: Should the maximum flash duration be calculated
from the frame interval (as described in the docs)?
Or is a "pretty high" constant maximum value preferred?

regards;rl

> 
> > >
> > > All register values are based on the OV9281 datasheet v1.53 (jan 2019)
> > > and tested using an ov9281 VisionComponents module.
> > >
> > > Signed-off-by: Richard Leitner <[e-mail]>
> > > ---
> > >  drivers/media/i2c/ov9282.c | 31 +++++++++++++++++++++++++++++++
> > >  1 file changed, 31 insertions(+)
> > >
> > > diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> > > index c98ba466e9aea29baff0b13578d760bf69c958c5..f7dfe8987e524b73af7e16e12567e96627b4f89a 100644
> > > --- a/drivers/media/i2c/ov9282.c
> > > +++ b/drivers/media/i2c/ov9282.c
> > > @@ -97,6 +97,10 @@
> > >  #define OV9282_REG_MIPI_CTRL00 0x4800
> > >  #define OV9282_GATED_CLOCK     BIT(5)
> > >
> > > +/* Flash/Strobe control registers */
> > > +#define OV9282_REG_FLASH_DURATION      0x3925
> > > +#define OV9282_FLASH_DURATION_DEFAULT  0x0000001A
> > > +
> > >  /* Input clock rate */
> > >  #define OV9282_INCLK_RATE      24000000
> > >
> > > @@ -193,6 +197,7 @@ struct ov9282_mode {
> > >   * @again_ctrl: Pointer to analog gain control
> > >   * @pixel_rate: Pointer to pixel rate control
> > >   * @flash_led_mode: Pointer to flash led mode control
> > > + * @flash_timeout: Pointer to flash timeout control
> > >   * @vblank: Vertical blanking in lines
> > >   * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
> > >   * @cur_mode: Pointer to current selected sensor mode
> > > @@ -216,6 +221,7 @@ struct ov9282 {
> > >         };
> > >         struct v4l2_ctrl *pixel_rate;
> > >         struct v4l2_ctrl *flash_led_mode;
> > > +       struct v4l2_ctrl *flash_timeout;
> >
> > You only access this in ov9282_set_ctrl where you already have the
> > struct v4l2_ctrl, so there is no need to store this in the main device
> > state.
> >
> >   Dave
> >
> > >         u32 vblank;
> > >         bool noncontinuous_clock;
> > >         const struct ov9282_mode *cur_mode;
> > > @@ -689,6 +695,24 @@ static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
> > >                                 current_val);
> > >  }
> > >
> > > +static int ov9282_set_ctrl_flash_timeout(struct ov9282 *ov9282, int value)
> > > +{
> > > +       /* Calculate "strobe_frame_span" increments from a given value (µs).
> > > +        * This is quite tricky as "The step width of shift and span is
> > > +        * programmable under system clock domain.", but it's not documented
> > > +        * how to program this step width (at least in the datasheet available
> > > +        * to the author at time of writing).
> > > +        * The formula below is interpolated from different modes/framerates
> > > +        * and should work quite well for most settings.
> > > +        */
> > > +       u32 val = value * 192 / (ov9282->cur_mode->width + ov9282->hblank_ctrl->val);
> > > +
> > > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION, 1, (val >> 24) & 0xff);
> > > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 1, 1, (val >> 16) & 0xff);
> > > +       ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 2, 1, (val >> 8) & 0xff);
> > > +       return ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 3, 1, val & 0xff);
> > > +}
> > > +
> > >  /**
> > >   * ov9282_set_ctrl() - Set subdevice control
> > >   * @ctrl: pointer to v4l2_ctrl structure
> > > @@ -758,6 +782,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
> > >         case V4L2_CID_FLASH_LED_MODE:
> > >                 ret = ov9282_set_ctrl_flash_led_mode(ov9282, ctrl->val);
> > >                 break;
> > > +       case V4L2_CID_FLASH_TIMEOUT:
> > > +               ret = ov9282_set_ctrl_flash_timeout(ov9282, ctrl->val);
> > > +               break;
> > >         default:
> > >                 dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
> > >                 ret = -EINVAL;
> > > @@ -1420,6 +1447,10 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
> > >                                                         (1 << V4L2_FLASH_LED_MODE_TORCH),
> > >                                                         V4L2_FLASH_LED_MODE_NONE);
> > >
> > > +       ov9282->flash_timeout = v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
> > > +                                                 V4L2_CID_FLASH_TIMEOUT,
> > > +                                                 0, 13900, 1, 8);
> > > +
> > >         ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
> > >         if (!ret) {
> > >                 /* Failure sets ctrl_hdlr->error, which we check afterwards anyway */
> > >
> > > --
> > > 2.47.2
> > >
> > >

Patch

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index c98ba466e9aea29baff0b13578d760bf69c958c5..f7dfe8987e524b73af7e16e12567e96627b4f89a 100644
--- a/drivers/media/i2c/ov9282.c
+++ b/drivers/media/i2c/ov9282.c
@@ -97,6 +97,10 @@ 
 #define OV9282_REG_MIPI_CTRL00	0x4800
 #define OV9282_GATED_CLOCK	BIT(5)
 
+/* Flash/Strobe control registers */
+#define OV9282_REG_FLASH_DURATION	0x3925
+#define OV9282_FLASH_DURATION_DEFAULT	0x0000001A
+
 /* Input clock rate */
 #define OV9282_INCLK_RATE	24000000
 
@@ -193,6 +197,7 @@  struct ov9282_mode {
  * @again_ctrl: Pointer to analog gain control
  * @pixel_rate: Pointer to pixel rate control
  * @flash_led_mode: Pointer to flash led mode control
+ * @flash_timeout: Pointer to flash timeout control
  * @vblank: Vertical blanking in lines
  * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
  * @cur_mode: Pointer to current selected sensor mode
@@ -216,6 +221,7 @@  struct ov9282 {
 	};
 	struct v4l2_ctrl *pixel_rate;
 	struct v4l2_ctrl *flash_led_mode;
+	struct v4l2_ctrl *flash_timeout;
 	u32 vblank;
 	bool noncontinuous_clock;
 	const struct ov9282_mode *cur_mode;
@@ -689,6 +695,24 @@  static int ov9282_set_ctrl_flash_led_mode(struct ov9282 *ov9282, int mode)
 				current_val);
 }
 
+static int ov9282_set_ctrl_flash_timeout(struct ov9282 *ov9282, int value)
+{
+	/* Calculate "strobe_frame_span" increments from a given value (µs).
+	 * This is quite tricky as "The step width of shift and span is
+	 * programmable under system clock domain.", but it's not documented
+	 * how to program this step width (at least in the datasheet available
+	 * to the author at time of writing).
+	 * The formula below is interpolated from different modes/framerates
+	 * and should work quite well for most settings.
+	 */
+	u32 val = value * 192 / (ov9282->cur_mode->width + ov9282->hblank_ctrl->val);
+
+	ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION, 1, (val >> 24) & 0xff);
+	ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 1, 1, (val >> 16) & 0xff);
+	ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 2, 1, (val >> 8) & 0xff);
+	return ov9282_write_reg(ov9282, OV9282_REG_FLASH_DURATION + 3, 1, val & 0xff);
+}
+
 /**
  * ov9282_set_ctrl() - Set subdevice control
  * @ctrl: pointer to v4l2_ctrl structure
@@ -758,6 +782,9 @@  static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
 	case V4L2_CID_FLASH_LED_MODE:
 		ret = ov9282_set_ctrl_flash_led_mode(ov9282, ctrl->val);
 		break;
+	case V4L2_CID_FLASH_TIMEOUT:
+		ret = ov9282_set_ctrl_flash_timeout(ov9282, ctrl->val);
+		break;
 	default:
 		dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
 		ret = -EINVAL;
@@ -1420,6 +1447,10 @@  static int ov9282_init_controls(struct ov9282 *ov9282)
 							(1 << V4L2_FLASH_LED_MODE_TORCH),
 							V4L2_FLASH_LED_MODE_NONE);
 
+	ov9282->flash_timeout = v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
+						  V4L2_CID_FLASH_TIMEOUT,
+						  0, 13900, 1, 8);
+
 	ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
 	if (!ret) {
 		/* Failure sets ctrl_hdlr->error, which we check afterwards anyway */