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[PATCH v8 7/8] media: i2c: ov9282: implement try_ctrl for strobe_duration

Richard Leitner posted 8 patches 3 months ago
There is a newer version of this series
[PATCH v8 7/8] media: i2c: ov9282: implement try_ctrl for strobe_duration
Posted by Richard Leitner 3 months ago 
As the granularity of the hardware supported values is lower than the
control value, implement a try_ctrl() function for
V4L2_CID_FLASH_DURATION. This function calculates the nearest possible
µs strobe duration for the given value and returns it back to the
caller.

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 drivers/media/i2c/ov9282.c | 55 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 52 insertions(+), 3 deletions(-)

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index 26296dc1d1b95..7aa74feb3ee44 100644
--- a/drivers/media/i2c/ov9282.c
+++ b/drivers/media/i2c/ov9282.c
@@ -128,6 +128,8 @@
 #define OV9282_REG_MIN		0x00
 #define OV9282_REG_MAX		0xfffff
 
+#define OV9282_STROBE_SPAN_FACTOR	192
+
 static const char * const ov9282_supply_names[] = {
 	"avdd",		/* Analog power */
 	"dovdd",	/* Digital I/O power */
@@ -691,9 +693,8 @@ static int ov9282_set_ctrl_flash_strobe_oe(struct ov9282 *ov9282, bool enable)
 	return ov9282_write_reg(ov9282, OV9282_REG_OUTPUT_ENABLE6, 1, current_val);
 }
 
-static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
+static u32 ov9282_us_to_flash_duration(struct ov9282 *ov9282, u32 value)
 {
-	int ret;
 	/*
 	 * Calculate "strobe_frame_span" increments from a given value (µs).
 	 * This is quite tricky as "The step width of shift and span is
@@ -703,7 +704,28 @@ static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
 	 * 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);
+	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
+
+	return value * OV9282_STROBE_SPAN_FACTOR / frame_width;
+}
+
+static u32 ov9282_flash_duration_to_us(struct ov9282 *ov9282, u32 value)
+{
+	/*
+	 * As the calculation in ov9282_us_to_flash_duration uses an integer
+	 * divison calculate in ns here to get more precision. Then check if
+	 * we need to compensate that divison by incrementing the µs result.
+	 */
+	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
+	u64 ns = value * 1000 * frame_width / OV9282_STROBE_SPAN_FACTOR;
+
+	return DIV_ROUND_UP(ns, 1000);
+}
+
+static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
+{
+	int ret;
+	u32 val = ov9282_us_to_flash_duration(ov9282, value);
 
 	ret = ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN, 1,
 			       (val >> 24) & 0xff);
@@ -798,9 +820,36 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
 	return ret;
 }
 
+static int ov9282_try_ctrl(struct v4l2_ctrl *ctrl)
+{
+	struct ov9282 *ov9282 =
+		container_of_const(ctrl->handler, struct ov9282, ctrl_handler);
+
+	if (ctrl->id == V4L2_CID_FLASH_DURATION) {
+		u32 us = ctrl->val;
+		u32 fd = ov9282_us_to_flash_duration(ov9282, us);
+
+		/* get nearest strobe_duration value */
+		u32 us0 = ov9282_flash_duration_to_us(ov9282, fd);
+		u32 us1 = ov9282_flash_duration_to_us(ov9282, fd + 1);
+
+		if (abs(us1 - us) < abs(us - us0))
+			ctrl->val = us1;
+		else
+			ctrl->val = us0;
+
+		if (us != ctrl->val)
+			dev_dbg(ov9282->dev, "using next valid strobe_duration %u instead of %u\n",
+				ctrl->val, us);
+	}
+
+	return 0;
+}
+
 /* V4l2 subdevice control ops*/
 static const struct v4l2_ctrl_ops ov9282_ctrl_ops = {
 	.s_ctrl = ov9282_set_ctrl,
+	.try_ctrl = ov9282_try_ctrl,
 };
 
 /**

-- 
2.47.3
Re: [PATCH v8 7/8] media: i2c: ov9282: implement try_ctrl for strobe_duration
Posted by Sakari Ailus 2 months, 4 weeks ago 
Hi Richard,

On Tue, Nov 04, 2025 at 03:30:58PM +0100, Richard Leitner wrote:
> As the granularity of the hardware supported values is lower than the
> control value, implement a try_ctrl() function for
> V4L2_CID_FLASH_DURATION. This function calculates the nearest possible
> µs strobe duration for the given value and returns it back to the
> caller.
> 
> Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
> ---
>  drivers/media/i2c/ov9282.c | 55 +++++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 52 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> index 26296dc1d1b95..7aa74feb3ee44 100644
> --- a/drivers/media/i2c/ov9282.c
> +++ b/drivers/media/i2c/ov9282.c
> @@ -128,6 +128,8 @@
>  #define OV9282_REG_MIN		0x00
>  #define OV9282_REG_MAX		0xfffff
>  
> +#define OV9282_STROBE_SPAN_FACTOR	192
> +
>  static const char * const ov9282_supply_names[] = {
>  	"avdd",		/* Analog power */
>  	"dovdd",	/* Digital I/O power */
> @@ -691,9 +693,8 @@ static int ov9282_set_ctrl_flash_strobe_oe(struct ov9282 *ov9282, bool enable)
>  	return ov9282_write_reg(ov9282, OV9282_REG_OUTPUT_ENABLE6, 1, current_val);
>  }
>  
> -static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
> +static u32 ov9282_us_to_flash_duration(struct ov9282 *ov9282, u32 value)
>  {
> -	int ret;
>  	/*
>  	 * Calculate "strobe_frame_span" increments from a given value (µs).
>  	 * This is quite tricky as "The step width of shift and span is
> @@ -703,7 +704,28 @@ static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
>  	 * 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);
> +	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
> +
> +	return value * OV9282_STROBE_SPAN_FACTOR / frame_width;
> +}
> +
> +static u32 ov9282_flash_duration_to_us(struct ov9282 *ov9282, u32 value)
> +{
> +	/*
> +	 * As the calculation in ov9282_us_to_flash_duration uses an integer
> +	 * divison calculate in ns here to get more precision. Then check if
> +	 * we need to compensate that divison by incrementing the µs result.
> +	 */
> +	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
> +	u64 ns = value * 1000 * frame_width / OV9282_STROBE_SPAN_FACTOR;
> +
> +	return DIV_ROUND_UP(ns, 1000);

Can ns even exceed U32_MAX? It doesn't seem to be useful to multiply and
then divide by 1000.

I guess this warrants v9, please fix the other issue for that, too.

> +}
> +
> +static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
> +{
> +	int ret;
> +	u32 val = ov9282_us_to_flash_duration(ov9282, value);
>  
>  	ret = ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN, 1,
>  			       (val >> 24) & 0xff);
> @@ -798,9 +820,36 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
>  	return ret;
>  }
>  
> +static int ov9282_try_ctrl(struct v4l2_ctrl *ctrl)
> +{
> +	struct ov9282 *ov9282 =
> +		container_of_const(ctrl->handler, struct ov9282, ctrl_handler);
> +
> +	if (ctrl->id == V4L2_CID_FLASH_DURATION) {
> +		u32 us = ctrl->val;
> +		u32 fd = ov9282_us_to_flash_duration(ov9282, us);
> +
> +		/* get nearest strobe_duration value */
> +		u32 us0 = ov9282_flash_duration_to_us(ov9282, fd);
> +		u32 us1 = ov9282_flash_duration_to_us(ov9282, fd + 1);
> +
> +		if (abs(us1 - us) < abs(us - us0))
> +			ctrl->val = us1;
> +		else
> +			ctrl->val = us0;
> +
> +		if (us != ctrl->val)
> +			dev_dbg(ov9282->dev, "using next valid strobe_duration %u instead of %u\n",
> +				ctrl->val, us);
> +	}
> +
> +	return 0;
> +}
> +
>  /* V4l2 subdevice control ops*/
>  static const struct v4l2_ctrl_ops ov9282_ctrl_ops = {
>  	.s_ctrl = ov9282_set_ctrl,
> +	.try_ctrl = ov9282_try_ctrl,
>  };
>  
>  /**
> 

-- 
Regards,

Sakari Ailus
Re: [PATCH v8 7/8] media: i2c: ov9282: implement try_ctrl for strobe_duration
Posted by Richard Leitner 2 months, 3 weeks ago 
Hi Sakari,

thanks for the quick feedback!

On Mon, Nov 10, 2025 at 09:55:18AM +0200, Sakari Ailus wrote:
> Hi Richard,
> 
> On Tue, Nov 04, 2025 at 03:30:58PM +0100, Richard Leitner wrote:
> > As the granularity of the hardware supported values is lower than the
> > control value, implement a try_ctrl() function for
> > V4L2_CID_FLASH_DURATION. This function calculates the nearest possible
> > µs strobe duration for the given value and returns it back to the
> > caller.
> > 
> > Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
> > ---
> >  drivers/media/i2c/ov9282.c | 55 +++++++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 52 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> > index 26296dc1d1b95..7aa74feb3ee44 100644
> > --- a/drivers/media/i2c/ov9282.c
> > +++ b/drivers/media/i2c/ov9282.c
> > @@ -128,6 +128,8 @@
> >  #define OV9282_REG_MIN		0x00
> >  #define OV9282_REG_MAX		0xfffff
> >  
> > +#define OV9282_STROBE_SPAN_FACTOR	192
> > +
> >  static const char * const ov9282_supply_names[] = {
> >  	"avdd",		/* Analog power */
> >  	"dovdd",	/* Digital I/O power */
> > @@ -691,9 +693,8 @@ static int ov9282_set_ctrl_flash_strobe_oe(struct ov9282 *ov9282, bool enable)
> >  	return ov9282_write_reg(ov9282, OV9282_REG_OUTPUT_ENABLE6, 1, current_val);
> >  }
> >  
> > -static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
> > +static u32 ov9282_us_to_flash_duration(struct ov9282 *ov9282, u32 value)
> >  {
> > -	int ret;
> >  	/*
> >  	 * Calculate "strobe_frame_span" increments from a given value (µs).
> >  	 * This is quite tricky as "The step width of shift and span is
> > @@ -703,7 +704,28 @@ static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
> >  	 * 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);
> > +	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
> > +
> > +	return value * OV9282_STROBE_SPAN_FACTOR / frame_width;
> > +}
> > +
> > +static u32 ov9282_flash_duration_to_us(struct ov9282 *ov9282, u32 value)
> > +{
> > +	/*
> > +	 * As the calculation in ov9282_us_to_flash_duration uses an integer
> > +	 * divison calculate in ns here to get more precision. Then check if
> > +	 * we need to compensate that divison by incrementing the µs result.
> > +	 */
> > +	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
> > +	u64 ns = value * 1000 * frame_width / OV9282_STROBE_SPAN_FACTOR;
> > +
> > +	return DIV_ROUND_UP(ns, 1000);
> 
> Can ns even exceed U32_MAX? It doesn't seem to be useful to multiply and
> then divide by 1000.

You're right. That multiply/divide by 1000 is obsolete. I will get rid
of it by calculating directly using DIV_ROUND_UP().

This will make the largest value "value * frame_width", which shouldn't
exceed U32_MAX in any real-world use-case IMHO...

> 
> I guess this warrants v9, please fix the other issue for that, too.
> 

Sure. Will send a v9 with both fixes later today. Thanks!

> > +}
> > +
> > +static int ov9282_set_ctrl_flash_duration(struct ov9282 *ov9282, u32 value)
> > +{
> > +	int ret;
> > +	u32 val = ov9282_us_to_flash_duration(ov9282, value);
> >  
> >  	ret = ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN, 1,
> >  			       (val >> 24) & 0xff);
> > @@ -798,9 +820,36 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
> >  	return ret;
> >  }
> >  
> > +static int ov9282_try_ctrl(struct v4l2_ctrl *ctrl)
> > +{
> > +	struct ov9282 *ov9282 =
> > +		container_of_const(ctrl->handler, struct ov9282, ctrl_handler);
> > +
> > +	if (ctrl->id == V4L2_CID_FLASH_DURATION) {
> > +		u32 us = ctrl->val;
> > +		u32 fd = ov9282_us_to_flash_duration(ov9282, us);
> > +
> > +		/* get nearest strobe_duration value */
> > +		u32 us0 = ov9282_flash_duration_to_us(ov9282, fd);
> > +		u32 us1 = ov9282_flash_duration_to_us(ov9282, fd + 1);
> > +
> > +		if (abs(us1 - us) < abs(us - us0))
> > +			ctrl->val = us1;
> > +		else
> > +			ctrl->val = us0;
> > +
> > +		if (us != ctrl->val)
> > +			dev_dbg(ov9282->dev, "using next valid strobe_duration %u instead of %u\n",
> > +				ctrl->val, us);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  /* V4l2 subdevice control ops*/
> >  static const struct v4l2_ctrl_ops ov9282_ctrl_ops = {
> >  	.s_ctrl = ov9282_set_ctrl,
> > +	.try_ctrl = ov9282_try_ctrl,
> >  };
> >  
> >  /**
> > 
> 
> -- 
> Regards,
> 
> Sakari Ailus

regards;rl
Re: [PATCH v8 7/8] media: i2c: ov9282: implement try_ctrl for strobe_duration
Posted by kernel test robot 3 months ago 
Hi Richard,

kernel test robot noticed the following build errors:

[auto build test ERROR on 2f112b1c25da9f5346c2261ed35c5b1e0b906471]

url:    https://github.com/intel-lab-lkp/linux/commits/Richard-Leitner/media-v4l-ctrls-add-a-control-for-flash-strobe-duration/20251104-225658
base:   2f112b1c25da9f5346c2261ed35c5b1e0b906471
patch link:    https://lore.kernel.org/r/20251104-ov9282-flash-strobe-v8-7-b91dfef1c65a%40linux.dev
patch subject: [PATCH v8 7/8] media: i2c: ov9282: implement try_ctrl for strobe_duration
config: xtensa-randconfig-001-20251107 (https://download.01.org/0day-ci/archive/20251108/202511080412.AYpJ1DIq-lkp@intel.com/config)
compiler: xtensa-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251108/202511080412.AYpJ1DIq-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511080412.AYpJ1DIq-lkp@intel.com/

All errors (new ones prefixed by >>):

>> xtensa-linux-ld: drivers/media/i2c/ov9282.o:(.text+0xc): undefined reference to `__udivdi3'
   xtensa-linux-ld: drivers/media/i2c/ov9282.o: in function `ov9282_try_ctrl':
>> ov9282.c:(.text+0x62): undefined reference to `__udivdi3'
   xtensa-linux-ld: drivers/media/i2c/ov9282.o:(.text+0x10): undefined reference to `__udivdi3'
   xtensa-linux-ld: drivers/media/i2c/ov9282.o: in function `ov9282_try_ctrl':
   ov9282.c:(.text+0x7e): undefined reference to `__udivdi3'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

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