[PATCH v6 00/11] Add strobe duration and hw strobe signal v4l2 ctrl & use it for ov9282

[Richard Leitner <richard.leitner@linux.dev>]

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_HW_STROBE_SIGNAL: "Hardware strobe signal": 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 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 (11):
      media: v4l: ctrls: add a control for flash/strobe duration
      media: v4l2-flash: add support for flash/strobe duration
      Documentation: uAPI: media: add V4L2_CID_FLASH_DURATION
      media: v4l: ctrls: add a control for enabling hw strobe signal
      Documentation: uAPI: media: add V4L2_CID_FLASH_HW_STROBE_SIGNAL
      media: i2c: ov9282: add output enable register definitions
      media: i2c: ov9282: add hardware strobe signal v4l2 control
      media: i2c: ov9282: add strobe_duration v4l2 control
      media: i2c: ov9282: add strobe_source 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    |  11 ++
 drivers/media/i2c/ov9282.c                         | 168 ++++++++++++++++++++-
 drivers/media/v4l2-core/v4l2-ctrls-defs.c          |   3 +
 drivers/media/v4l2-core/v4l2-flash-led-class.c     |  25 +++
 include/uapi/linux/v4l2-controls.h                 |   2 +
 5 files changed, 203 insertions(+), 6 deletions(-)
---
base-commit: d9946fe286439c2aeaa7953b8c316efe5b83d515
change-id: 20250303-ov9282-flash-strobe-ac6bd00c9de6

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