linux-kernel - Re: [PATCH v10 0/8] Add strobe duration and strobe output enable v4l2 ctrl

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Message-ID: <lwib4og3xnpmqrvmkenp5m6qywuzwmzilpdh74ugx2jfbm2s2o@zyvplzxtkepo>
Date: Tue, 30 Dec 2025 11:08:58 +0100
From: Richard Leitner <richard.leitner@...ux.dev>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Dave Stevenson <dave.stevenson@...pberrypi.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>, 
	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-leds@...r.kernel.org, Hans Verkuil <hverkuil@...nel.org>
Subject: Re: [PATCH v10 0/8] Add strobe duration and strobe output enable
 v4l2 ctrl

Hi again,

just wanted to mention that I'll be doing a short (10 min) talk on this
topic at FOSDEM 2026 in the Embedded, Mobile and Automotive devroom on
sunday: https://fosdem.org/2026/schedule/event/A7P7XE-v4l2-flash-control/

Would be great if I could get some more - maybe final ;) - review on
this series before FOSDEM. Thanks!

regards;rl

On Thu, Dec 18, 2025 at 08:22:53AM +0100, Richard Leitner wrote:
> Hi everybody,
> 
> just a friendly ping before the holiday season kicks in :-)
> 
> regards;rl
> 
> On Tue, Dec 09, 2025 at 11:44:35PM +0100, Richard Leitner wrote:
> > 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@...ux.dev>
> > ---
> > Changes in v10:
> > - Avoid bitwise or on error codes in ov9282_set_ctrl_flash_duration() (Thanks Sakari)
> > - Link to v9: https://patch.msgid.link/20251120-ov9282-flash-strobe-v9-0-6c9e3a4301d7@linux.dev
> > 
> > Changes in v9:
> > - Avoid needless multiplication/division in ov9282.c (Thanks Sakari)
> > - Avoid possible u32 overflow in ov9282.c (Thanks Sakari)
> > - Link to v8: https://patch.msgid.link/20251104-ov9282-flash-strobe-v8-0-b91dfef1c65a@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                         | 174 ++++++++++++++++++++-
> >  drivers/media/v4l2-core/v4l2-ctrls-defs.c          |   3 +
> >  include/uapi/linux/v4l2-controls.h                 |   2 +
> >  4 files changed, 215 insertions(+), 6 deletions(-)
> > ---
> > base-commit: 2f112b1c25da9f5346c2261ed35c5b1e0b906471
> > change-id: 20250303-ov9282-flash-strobe-ac6bd00c9de6
> > 
> > Best regards,
> > --  
> > Richard Leitner <richard.leitner@...ux.dev>
> > 
> >