[PATCH v8 0/8] Add strobe duration and strobe output enable v4l2 ctrl

[PATCH v8 0/8] Add strobe duration and strobe output enable v4l2 ctrl

[Richard Leitner]

This series adds two new v4l2 controls:
- V4L2_CID_FLASH_DURATION: "Strobe duration": This control enables
  setting a desired flash/strobe length/duration in µs.
- V4L2_CID_FLASH_STROBE_OE: "Strobe output enable": This
  control enables the hardware strobe output signal of a v4l2 device.

As a first user of these new controls add basic flash/strobe support
for ov9282 sensors using their "hardware strobe output". The duration
calculation is only interpolated from various measurements, as no
documentation was found.

Further flash/strobe-related controls as well as a migration to v4l2-cci
helpers for ov9282 will likely be implemented in future series.

All register addresses/values are based on the OV9281 datasheet v1.53
(january 2019). This series was tested using an ov9281 VisionComponents
camera module.

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
Changes in v8:
- Minor styling changes across the set
- Add missing error handling for ov9282 strobe_frame_span writing
- Rename V4L2_CID_FLASH_HW_STROBE_SIGNAL to V4L2_CID_FLASH_STROBE_OE
- Drop 02/10: FLASH_DURATION handling in v4l2-flash
- Drop 08/10: strobe_source in ov9282
- Link to v7: https://lore.kernel.org/r/20250901-ov9282-flash-strobe-v7-0-d58d5a694afc@linux.dev

Changes in v7:
- Improved v4l2 uAPI documentation (thanks Sakari)
- Link to v6: https://lore.kernel.org/r/20250716-ov9282-flash-strobe-v6-0-934f12aeff33@linux.dev

Changes in v6:
- Fix "Alignment should match open parenthesis" by Media-CI bot in v4l2-flash-led-class.c
- Fix "format string contains non-ascii character (µ)" by Media-CI bot in ov9282.c
- Introduce new V4L2_CID_FLASH_HW_STROBE_SIGNAL control (as suggested by Sakari)
- Implement V4L2_CID_FLASH_HW_STROBE_SIGNAL instead of
  V4L2_CID_FLASH_LED_MODE in ov9282.c (as suggested by Sakari)
- Drop "media: v4l2-flash: fix flash_timeout comment" as this was
  applied (thanks Lee)
- Link to v5: https://lore.kernel.org/r/20250617-ov9282-flash-strobe-v5-0-9762da74d065@linux.dev

Changes in v5:
- Improve try_ctrl for flash_duration by using DIV_ROUND_UP() and abs() (thanks Sakari)
- Drop "leds: flash: Add support for flash/strobe duration" as this was applied upstream
- Add "media: i2c: ov9282: dynamic flash_duration maximum" (thanks Sakari)
- Link to v4: https://lore.kernel.org/r/20250507-ov9282-flash-strobe-v4-0-72b299c1b7c9@linux.dev

Changes in v4:
- Fix FLASH_DURATION implementation in v4l2-flash-led-class.c by adding a
  missing brace and enum entry (thanks Sakari)
- Fix format of multiline comment in ov9282.c (thanks Sakari)
- Add missing NULL check in ov9282.c (thanks Sakari)
- Adapt nr_of_controls_hint for v4l2 handler in ov9282.c (thanks Sakari)
- Add patch for implementing try_ctrl for strobe_duration (thanks Sakari)
- Link to v3: https://lore.kernel.org/r/20250429-ov9282-flash-strobe-v3-0-2105ce179952@linux.dev

Changes in v3:
- create separate patch for leds driver changes (thanks Lee)
- Link to v2: https://lore.kernel.org/r/20250314-ov9282-flash-strobe-v2-0-14d7a281342d@linux.dev

Changes in v2:
- remove not needed controls in struct ov9282 (thanks Dave)
- Fix commit message of 3/3 regarding framerate get/set (thanks Dave)
- Add V4L2_CID_FLASH_STROBE_SOURCE impementation to ov9282
- Add new V4L2_CID_FLASH_DURATION control (as suggested by Laurent)
- Use FLASH_DURATION instead of FLASH_TIMEOUT for ov9282
- Link to v1: https://lore.kernel.org/r/20250303-ov9282-flash-strobe-v1-0-0fd57a1564ba@linux.dev

---
Richard Leitner (8):
      media: v4l: ctrls: add a control for flash/strobe duration
      media: v4l: ctrls: add a control for enabling strobe output
      Documentation: uAPI: media: add V4L2_CID_FLASH_{DURATION,STROBE_OE}
      media: i2c: ov9282: add output enable register definitions
      media: i2c: ov9282: add strobe output enable v4l2 control
      media: i2c: ov9282: add strobe_duration v4l2 control
      media: i2c: ov9282: implement try_ctrl for strobe_duration
      media: i2c: ov9282: dynamic flash_duration maximum

 .../userspace-api/media/v4l/ext-ctrls-flash.rst    |  42 ++++++
 drivers/media/i2c/ov9282.c                         | 165 ++++++++++++++++++++-
 drivers/media/v4l2-core/v4l2-ctrls-defs.c          |   3 +
 include/uapi/linux/v4l2-controls.h                 |   2 +
 4 files changed, 206 insertions(+), 6 deletions(-)
---
base-commit: 2f112b1c25da9f5346c2261ed35c5b1e0b906471
change-id: 20250303-ov9282-flash-strobe-ac6bd00c9de6

Best regards,
--  
Richard Leitner <richard.leitner@linux.dev>

[PATCH v8 1/8] media: v4l: ctrls: add a control for flash/strobe duration

[Richard Leitner]

Add a V4L2_CID_FLASH_DURATION control to set the duration of a
flash/strobe pulse. This controls the length of the flash/strobe pulse
output by device (typically a camera sensor) and connected to the flash
controller. This is different to the V4L2_CID_FLASH_TIMEOUT control,
which is implemented by the flash controller and defines a limit after
which the flash is "forcefully" turned off again.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 drivers/media/v4l2-core/v4l2-ctrls-defs.c | 1 +
 include/uapi/linux/v4l2-controls.h        | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
index ad41f65374e23..4848423205ff7 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
@@ -1135,6 +1135,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_FLASH_FAULT:		return "Faults";
 	case V4L2_CID_FLASH_CHARGE:		return "Charge";
 	case V4L2_CID_FLASH_READY:		return "Ready to Strobe";
+	case V4L2_CID_FLASH_DURATION:		return "Strobe Duration";
 
 	/* JPEG encoder controls */
 	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 2d30107e047ee..9830833b48a52 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -1186,6 +1186,7 @@ enum v4l2_flash_strobe_source {
 
 #define V4L2_CID_FLASH_CHARGE			(V4L2_CID_FLASH_CLASS_BASE + 11)
 #define V4L2_CID_FLASH_READY			(V4L2_CID_FLASH_CLASS_BASE + 12)
+#define V4L2_CID_FLASH_DURATION			(V4L2_CID_FLASH_CLASS_BASE + 13)
 
 
 /* JPEG-class control IDs */

-- 
2.47.3

[PATCH v8 2/8] media: v4l: ctrls: add a control for enabling strobe output

[Richard Leitner]

Add a control V4L2_CID_FLASH_STROBE_OE to en- or disable the
strobe output of v4l2 devices (most likely sensors).

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 drivers/media/v4l2-core/v4l2-ctrls-defs.c | 2 ++
 include/uapi/linux/v4l2-controls.h        | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
index 4848423205ff7..765aeeec84fe5 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
@@ -1136,6 +1136,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_FLASH_CHARGE:		return "Charge";
 	case V4L2_CID_FLASH_READY:		return "Ready to Strobe";
 	case V4L2_CID_FLASH_DURATION:		return "Strobe Duration";
+	case V4L2_CID_FLASH_STROBE_OE:		return "Strobe Output Enable";
 
 	/* JPEG encoder controls */
 	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
@@ -1282,6 +1283,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
 	case V4L2_CID_FLASH_STROBE_STATUS:
 	case V4L2_CID_FLASH_CHARGE:
 	case V4L2_CID_FLASH_READY:
+	case V4L2_CID_FLASH_STROBE_OE:
 	case V4L2_CID_MPEG_VIDEO_DECODER_MPEG4_DEBLOCK_FILTER:
 	case V4L2_CID_MPEG_VIDEO_DECODER_SLICE_INTERFACE:
 	case V4L2_CID_MPEG_VIDEO_DEC_DISPLAY_DELAY_ENABLE:
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 9830833b48a52..32ba3b5fb1dd5 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -1187,6 +1187,7 @@ enum v4l2_flash_strobe_source {
 #define V4L2_CID_FLASH_CHARGE			(V4L2_CID_FLASH_CLASS_BASE + 11)
 #define V4L2_CID_FLASH_READY			(V4L2_CID_FLASH_CLASS_BASE + 12)
 #define V4L2_CID_FLASH_DURATION			(V4L2_CID_FLASH_CLASS_BASE + 13)
+#define V4L2_CID_FLASH_STROBE_OE		(V4L2_CID_FLASH_CLASS_BASE + 14)
 
 
 /* JPEG-class control IDs */

-- 
2.47.3

[PATCH v8 3/8] Documentation: uAPI: media: add V4L2_CID_FLASH_{DURATION,STROBE_OE}

[Richard Leitner]

Add the new strobe duration and hardware strobe output enable to v4l
uAPI documentation. Additionally add labels for cross-referencing v4l
controls.

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 .../userspace-api/media/v4l/ext-ctrls-flash.rst    | 42 ++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
index d22c5efb806a1..7cf0d33e79ff0 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-flash.rst
@@ -57,6 +57,8 @@ Flash Control IDs
 ``V4L2_CID_FLASH_CLASS (class)``
     The FLASH class descriptor.
 
+.. _v4l2-cid-flash-led-mode:
+
 ``V4L2_CID_FLASH_LED_MODE (menu)``
     Defines the mode of the flash LED, the high-power white LED attached
     to the flash controller. Setting this control may not be possible in
@@ -80,6 +82,8 @@ Flash Control IDs
 
 
 
+.. _v4l2-cid-flash-strobe-source:
+
 ``V4L2_CID_FLASH_STROBE_SOURCE (menu)``
     Defines the source of the flash LED strobe.
 
@@ -96,6 +100,12 @@ Flash Control IDs
       - The flash strobe is triggered by an external source. Typically
 	this is a sensor, which makes it possible to synchronise the
 	flash strobe start to exposure start.
+        This method of controlling flash LED strobe has two additional
+        prerequisites: the strobe source's :ref:`strobe output
+        <v4l2-cid-flash-strobe-oe>` must be enabled (if available)
+        and the flash controller's :ref:`flash LED mode
+        <v4l2-cid-flash-led-mode>` must be set to
+        ``V4L2_FLASH_LED_MODE_FLASH``.
 
 
 
@@ -186,3 +196,35 @@ Flash Control IDs
     charged before strobing. LED flashes often require a cooldown period
     after strobe during which another strobe will not be possible. This
     is a read-only control.
+
+.. _v4l2-cid-flash-duration:
+
+``V4L2_CID_FLASH_DURATION (integer)``
+    Duration of the flash strobe pulse generated by the strobe source, when
+    using external strobe. This control shall be implemented by the device
+    generating the hardware flash strobe signal, typically a camera sensor,
+    connected to a flash controller.
+
+    The flash controllers :ref:`strobe source <v4l2-cid-flash-strobe-source>`
+    must be configured to ``V4L2_FLASH_STROBE_SOURCE_EXTERNAL`` for this
+    mode of operation. For more details please also take a look at the
+    documentation there.
+
+    The unit should be microseconds (µs) if possible.
+
+.. _v4l2-cid-flash-strobe-oe:
+
+``V4L2_CID_FLASH_STROBE_OE (boolean)``
+    Enables the output of a hardware strobe signal from the strobe source,
+    when using external strobe. This control shall be implemented by the device
+    generating the hardware flash strobe signal, typically a camera sensor,
+    connected to a flash controller.
+
+    Provided the signal generating device driver supports it, the length of the
+    strobe signal can be configured by adjusting its
+    :ref:`flash duration <v4l2-cid-flash-duration>`.
+
+    The flash controllers :ref:`strobe source <v4l2-cid-flash-strobe-source>`
+    must be configured to ``V4L2_FLASH_STROBE_SOURCE_EXTERNAL`` for this
+    mode of operation. For more details please also take a look at the
+    documentation there.

-- 
2.47.3

[PATCH v8 4/8] media: i2c: ov9282: add output enable register definitions

[Richard Leitner]

Add #define's for the output enable registers (0x3004, 0x3005, 0x3006),
also known as SC_CTRL_04, SC_CTRL_05, SC_CTRL_04. Use those register
definitions instead of the raw values in the `common_regs` struct.

All values are based on the OV9281 datasheet v1.53 (january 2019).

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 drivers/media/i2c/ov9282.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index a9f6176e9729d..e67cff6c30ffa 100644
--- a/drivers/media/i2c/ov9282.c
+++ b/drivers/media/i2c/ov9282.c
@@ -37,6 +37,29 @@
 #define OV9282_REG_ID		0x300a
 #define OV9282_ID		0x9281
 
+/* Output enable registers */
+#define OV9282_REG_OUTPUT_ENABLE4	0x3004
+#define OV9282_OUTPUT_ENABLE4_GPIO2	BIT(1)
+#define OV9282_OUTPUT_ENABLE4_D9	BIT(0)
+
+#define OV9282_REG_OUTPUT_ENABLE5	0x3005
+#define OV9282_OUTPUT_ENABLE5_D8	BIT(7)
+#define OV9282_OUTPUT_ENABLE5_D7	BIT(6)
+#define OV9282_OUTPUT_ENABLE5_D6	BIT(5)
+#define OV9282_OUTPUT_ENABLE5_D5	BIT(4)
+#define OV9282_OUTPUT_ENABLE5_D4	BIT(3)
+#define OV9282_OUTPUT_ENABLE5_D3	BIT(2)
+#define OV9282_OUTPUT_ENABLE5_D2	BIT(1)
+#define OV9282_OUTPUT_ENABLE5_D1	BIT(0)
+
+#define OV9282_REG_OUTPUT_ENABLE6	0x3006
+#define OV9282_OUTPUT_ENABLE6_D0	BIT(7)
+#define OV9282_OUTPUT_ENABLE6_PCLK	BIT(6)
+#define OV9282_OUTPUT_ENABLE6_HREF	BIT(5)
+#define OV9282_OUTPUT_ENABLE6_STROBE	BIT(3)
+#define OV9282_OUTPUT_ENABLE6_ILPWM	BIT(2)
+#define OV9282_OUTPUT_ENABLE6_VSYNC	BIT(1)
+
 /* Exposure control */
 #define OV9282_REG_EXPOSURE	0x3500
 #define OV9282_EXPOSURE_MIN	1
@@ -213,9 +236,9 @@ static const struct ov9282_reg common_regs[] = {
 	{0x0302, 0x32},
 	{0x030e, 0x02},
 	{0x3001, 0x00},
-	{0x3004, 0x00},
-	{0x3005, 0x00},
-	{0x3006, 0x04},
+	{OV9282_REG_OUTPUT_ENABLE4, 0x00},
+	{OV9282_REG_OUTPUT_ENABLE5, 0x00},
+	{OV9282_REG_OUTPUT_ENABLE6, OV9282_OUTPUT_ENABLE6_ILPWM},
 	{0x3011, 0x0a},
 	{0x3013, 0x18},
 	{0x301c, 0xf0},

-- 
2.47.3

[PATCH v8 5/8] media: i2c: ov9282: add strobe output enable v4l2 control

[Richard Leitner]

Add V4L2_CID_FLASH_STROBE_OE enable/disable support using the
"strobe output enable" feature of the sensor.

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

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 drivers/media/i2c/ov9282.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index e67cff6c30ffa..6afce803a049d 100644
--- a/drivers/media/i2c/ov9282.c
+++ b/drivers/media/i2c/ov9282.c
@@ -670,6 +670,23 @@ static int ov9282_set_ctrl_vflip(struct ov9282 *ov9282, int value)
 				current_val);
 }
 
+static int ov9282_set_ctrl_flash_strobe_oe(struct ov9282 *ov9282, bool enable)
+{
+	u32 current_val;
+	int ret;
+
+	ret = ov9282_read_reg(ov9282, OV9282_REG_OUTPUT_ENABLE6, 1, &current_val);
+	if (ret)
+		return ret;
+
+	if (enable)
+		current_val |= OV9282_OUTPUT_ENABLE6_STROBE;
+	else
+		current_val &= ~OV9282_OUTPUT_ENABLE6_STROBE;
+
+	return ov9282_write_reg(ov9282, OV9282_REG_OUTPUT_ENABLE6, 1, current_val);
+}
+
 /**
  * ov9282_set_ctrl() - Set subdevice control
  * @ctrl: pointer to v4l2_ctrl structure
@@ -736,6 +753,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
 		ret = ov9282_write_reg(ov9282, OV9282_REG_TIMING_HTS, 2,
 				       (ctrl->val + ov9282->cur_mode->width) >> 1);
 		break;
+	case V4L2_CID_FLASH_STROBE_OE:
+		ret = ov9282_set_ctrl_flash_strobe_oe(ov9282, ctrl->val);
+		break;
 	default:
 		dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
 		ret = -EINVAL;
@@ -1325,7 +1345,7 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 	u32 lpfr;
 	int ret;
 
-	ret = v4l2_ctrl_handler_init(ctrl_hdlr, 10);
+	ret = v4l2_ctrl_handler_init(ctrl_hdlr, 11);
 	if (ret)
 		return ret;
 
@@ -1390,6 +1410,10 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 						OV9282_TIMING_HTS_MAX - mode->width,
 						1, hblank_min);
 
+	/* Flash/Strobe controls */
+	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
+			  V4L2_CID_FLASH_STROBE_OE, 0, 1, 1, 0);
+
 	ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
 	if (!ret) {
 		/* Failure sets ctrl_hdlr->error, which we check afterwards anyway */

-- 
2.47.3

[PATCH v8 6/8] media: i2c: ov9282: add strobe_duration v4l2 control

[Richard Leitner]

Add V4L2_CID_FLASH_DURATION 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 default
framerate.

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 <richard.leitner@linux.dev>
---
 drivers/media/i2c/ov9282.c | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index 6afce803a049d..26296dc1d1b95 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_STROBE_FRAME_SPAN		0x3925
+#define OV9282_STROBE_FRAME_SPAN_DEFAULT	0x0000001a
+
 /* Input clock rate */
 #define OV9282_INCLK_RATE	24000000
 
@@ -687,6 +691,31 @@ 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)
+{
+	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
+	 * 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);
+
+	ret = ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN, 1,
+			       (val >> 24) & 0xff);
+	ret |= ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN + 1, 1,
+				(val >> 16) & 0xff);
+	ret |= ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN + 2, 1,
+				(val >> 8) & 0xff);
+	ret |= ov9282_write_reg(ov9282, OV9282_REG_STROBE_FRAME_SPAN + 3, 1,
+				val & 0xff);
+	return ret;
+}
+
 /**
  * ov9282_set_ctrl() - Set subdevice control
  * @ctrl: pointer to v4l2_ctrl structure
@@ -756,6 +785,9 @@ static int ov9282_set_ctrl(struct v4l2_ctrl *ctrl)
 	case V4L2_CID_FLASH_STROBE_OE:
 		ret = ov9282_set_ctrl_flash_strobe_oe(ov9282, ctrl->val);
 		break;
+	case V4L2_CID_FLASH_DURATION:
+		ret = ov9282_set_ctrl_flash_duration(ov9282, ctrl->val);
+		break;
 	default:
 		dev_err(ov9282->dev, "Invalid control %d", ctrl->id);
 		ret = -EINVAL;
@@ -1345,7 +1377,7 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 	u32 lpfr;
 	int ret;
 
-	ret = v4l2_ctrl_handler_init(ctrl_hdlr, 11);
+	ret = v4l2_ctrl_handler_init(ctrl_hdlr, 12);
 	if (ret)
 		return ret;
 
@@ -1414,6 +1446,9 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
 			  V4L2_CID_FLASH_STROBE_OE, 0, 1, 1, 0);
 
+	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
+			  0, 13900, 1, 8);
+
 	ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
 	if (!ret) {
 		/* Failure sets ctrl_hdlr->error, which we check afterwards anyway */

-- 
2.47.3

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

[Richard Leitner]

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

[kernel test robot]

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

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

[Sakari Ailus]

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

[PATCH v8 8/8] media: i2c: ov9282: dynamic flash_duration maximum

[Richard Leitner]

This patch sets the current exposure time as maximum for the
flash_duration control. As Flash/Strobes which are longer than the
exposure time have no effect.

Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
---
 drivers/media/i2c/ov9282.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
index 7aa74feb3ee44..df7beedba0b9e 100644
--- a/drivers/media/i2c/ov9282.c
+++ b/drivers/media/i2c/ov9282.c
@@ -198,6 +198,7 @@ struct ov9282_mode {
  * @exp_ctrl: Pointer to exposure control
  * @again_ctrl: Pointer to analog gain control
  * @pixel_rate: Pointer to pixel rate control
+ * @flash_duration: Pointer to flash duration control
  * @vblank: Vertical blanking in lines
  * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
  * @cur_mode: Pointer to current selected sensor mode
@@ -220,6 +221,7 @@ struct ov9282 {
 		struct v4l2_ctrl *again_ctrl;
 	};
 	struct v4l2_ctrl *pixel_rate;
+	struct v4l2_ctrl *flash_duration;
 	u32 vblank;
 	bool noncontinuous_clock;
 	const struct ov9282_mode *cur_mode;
@@ -611,6 +613,15 @@ static int ov9282_update_controls(struct ov9282 *ov9282,
 					mode->vblank_max, 1, mode->vblank);
 }
 
+static u32 ov9282_exposure_to_us(struct ov9282 *ov9282, u32 exposure)
+{
+	/* calculate exposure time in µs */
+	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
+	u32 trow_us = frame_width * 1000000UL / ov9282->pixel_rate->val;
+
+	return exposure * trow_us;
+}
+
 /**
  * ov9282_update_exp_gain() - Set updated exposure and gain
  * @ov9282: pointer to ov9282 device
@@ -622,9 +633,10 @@ static int ov9282_update_controls(struct ov9282 *ov9282,
 static int ov9282_update_exp_gain(struct ov9282 *ov9282, u32 exposure, u32 gain)
 {
 	int ret;
+	u32 exposure_us = ov9282_exposure_to_us(ov9282, exposure);
 
-	dev_dbg(ov9282->dev, "Set exp %u, analog gain %u",
-		exposure, gain);
+	dev_dbg(ov9282->dev, "Set exp %u (~%u us), analog gain %u",
+		exposure, exposure_us, gain);
 
 	ret = ov9282_write_reg(ov9282, OV9282_REG_HOLD, 1, 1);
 	if (ret)
@@ -635,6 +647,12 @@ static int ov9282_update_exp_gain(struct ov9282 *ov9282, u32 exposure, u32 gain)
 		goto error_release_group_hold;
 
 	ret = ov9282_write_reg(ov9282, OV9282_REG_AGAIN, 1, gain);
+	if (ret)
+		goto error_release_group_hold;
+
+	ret = __v4l2_ctrl_modify_range(ov9282->flash_duration,
+				       0, exposure_us, 1,
+				       OV9282_STROBE_FRAME_SPAN_DEFAULT);
 
 error_release_group_hold:
 	ov9282_write_reg(ov9282, OV9282_REG_HOLD, 1, 0);
@@ -1423,6 +1441,7 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 	const struct ov9282_mode *mode = ov9282->cur_mode;
 	struct v4l2_fwnode_device_properties props;
 	u32 hblank_min;
+	u32 exposure_us;
 	u32 lpfr;
 	int ret;
 
@@ -1495,8 +1514,11 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
 	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
 			  V4L2_CID_FLASH_STROBE_OE, 0, 1, 1, 0);
 
-	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
-			  0, 13900, 1, 8);
+	exposure_us = ov9282_exposure_to_us(ov9282, OV9282_EXPOSURE_DEFAULT);
+	ov9282->flash_duration = v4l2_ctrl_new_std(ctrl_hdlr,
+						   &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
+						   0, exposure_us,
+						   1, OV9282_STROBE_FRAME_SPAN_DEFAULT);
 
 	ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
 	if (!ret) {

-- 
2.47.3

Re: [PATCH v8 8/8] media: i2c: ov9282: dynamic flash_duration maximum

[Sakari Ailus]

On Tue, Nov 04, 2025 at 03:30:59PM +0100, Richard Leitner wrote:
> This patch sets the current exposure time as maximum for the
> flash_duration control. As Flash/Strobes which are longer than the
> exposure time have no effect.
> 
> Signed-off-by: Richard Leitner <richard.leitner@linux.dev>
> ---
>  drivers/media/i2c/ov9282.c | 30 ++++++++++++++++++++++++++----
>  1 file changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov9282.c b/drivers/media/i2c/ov9282.c
> index 7aa74feb3ee44..df7beedba0b9e 100644
> --- a/drivers/media/i2c/ov9282.c
> +++ b/drivers/media/i2c/ov9282.c
> @@ -198,6 +198,7 @@ struct ov9282_mode {
>   * @exp_ctrl: Pointer to exposure control
>   * @again_ctrl: Pointer to analog gain control
>   * @pixel_rate: Pointer to pixel rate control
> + * @flash_duration: Pointer to flash duration control
>   * @vblank: Vertical blanking in lines
>   * @noncontinuous_clock: Selection of CSI2 noncontinuous clock mode
>   * @cur_mode: Pointer to current selected sensor mode
> @@ -220,6 +221,7 @@ struct ov9282 {
>  		struct v4l2_ctrl *again_ctrl;
>  	};
>  	struct v4l2_ctrl *pixel_rate;
> +	struct v4l2_ctrl *flash_duration;
>  	u32 vblank;
>  	bool noncontinuous_clock;
>  	const struct ov9282_mode *cur_mode;
> @@ -611,6 +613,15 @@ static int ov9282_update_controls(struct ov9282 *ov9282,
>  					mode->vblank_max, 1, mode->vblank);
>  }
>  
> +static u32 ov9282_exposure_to_us(struct ov9282 *ov9282, u32 exposure)
> +{
> +	/* calculate exposure time in µs */
> +	u32 frame_width = ov9282->cur_mode->width + ov9282->hblank_ctrl->val;
> +	u32 trow_us = frame_width * 1000000UL / ov9282->pixel_rate->val;

This can overflow.

> +
> +	return exposure * trow_us;
> +}
> +
>  /**
>   * ov9282_update_exp_gain() - Set updated exposure and gain
>   * @ov9282: pointer to ov9282 device
> @@ -622,9 +633,10 @@ static int ov9282_update_controls(struct ov9282 *ov9282,
>  static int ov9282_update_exp_gain(struct ov9282 *ov9282, u32 exposure, u32 gain)
>  {
>  	int ret;
> +	u32 exposure_us = ov9282_exposure_to_us(ov9282, exposure);
>  
> -	dev_dbg(ov9282->dev, "Set exp %u, analog gain %u",
> -		exposure, gain);
> +	dev_dbg(ov9282->dev, "Set exp %u (~%u us), analog gain %u",
> +		exposure, exposure_us, gain);
>  
>  	ret = ov9282_write_reg(ov9282, OV9282_REG_HOLD, 1, 1);
>  	if (ret)
> @@ -635,6 +647,12 @@ static int ov9282_update_exp_gain(struct ov9282 *ov9282, u32 exposure, u32 gain)
>  		goto error_release_group_hold;
>  
>  	ret = ov9282_write_reg(ov9282, OV9282_REG_AGAIN, 1, gain);
> +	if (ret)
> +		goto error_release_group_hold;
> +
> +	ret = __v4l2_ctrl_modify_range(ov9282->flash_duration,
> +				       0, exposure_us, 1,
> +				       OV9282_STROBE_FRAME_SPAN_DEFAULT);
>  
>  error_release_group_hold:
>  	ov9282_write_reg(ov9282, OV9282_REG_HOLD, 1, 0);
> @@ -1423,6 +1441,7 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
>  	const struct ov9282_mode *mode = ov9282->cur_mode;
>  	struct v4l2_fwnode_device_properties props;
>  	u32 hblank_min;
> +	u32 exposure_us;
>  	u32 lpfr;
>  	int ret;
>  
> @@ -1495,8 +1514,11 @@ static int ov9282_init_controls(struct ov9282 *ov9282)
>  	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops,
>  			  V4L2_CID_FLASH_STROBE_OE, 0, 1, 1, 0);
>  
> -	v4l2_ctrl_new_std(ctrl_hdlr, &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
> -			  0, 13900, 1, 8);
> +	exposure_us = ov9282_exposure_to_us(ov9282, OV9282_EXPOSURE_DEFAULT);
> +	ov9282->flash_duration = v4l2_ctrl_new_std(ctrl_hdlr,
> +						   &ov9282_ctrl_ops, V4L2_CID_FLASH_DURATION,
> +						   0, exposure_us,
> +						   1, OV9282_STROBE_FRAME_SPAN_DEFAULT);
>  
>  	ret = v4l2_fwnode_device_parse(ov9282->dev, &props);
>  	if (!ret) {
> 

-- 
Kind regards,

Sakari Ailus