[RFC PATCH v3 0/2] media: i2c: Add onsemi AR0234 camera sensor driver

[Alexander Shiyan <eagle.alexander923@gmail.com>]

This series adds a driver for the onsemi AR0234 CMOS image sensor.
The AR0234 is a 1/2.6-inch global-shutter sensor with a 1940x1220
pixel array, capable of 1920x1200 resolution at up to 120 fps.
It supports MIPI CSI-2 output with 1 to 4 data lanes, raw Bayer
(8/10-bit) and monochrome formats, as well as DPCM 10->8 compression.

The driver has been tested with 2 and 4 lanes on an ARM64 Rockchip
RK3568 platform with a 27 MHz external clock. Both 8-bit and 10-bit
raw Bayer modes are functional.

Notes:
- 1-lane mode is currently disabled; attempts to use it produced no
  valid image. Further investigation is needed.
- The driver uses a private streaming flag to protect cropping changes
  during streaming. Is this the recommended approach, or should we
  rely solely on the subdev state?
- The DPCM (10->8 compression) mode is included in the code but could
  not be tested due to lack of suitable hardware; any testing help
  would be appreciated.

Changes since v2:
- Added devicetree binding documentation for the onsemi AR0234 sensor.
- Added support for 8-bit raw Bayer output (verified working).
- Added DPCM 10->8 compression mode (untested, included for
  completeness).
- Reworked mode handling: each mode now specifies input/output bpp,
  DPCM flag, MIPI data type, and link frequency index.
- Reworked link frequency handling: the driver now accepts any valid
  link frequencies from the device tree. It expects two frequencies -
  one for 8-bit mode and one for 10-bit mode - but does not enforce
  a fixed set; frequencies are validated by attempting PLL calculation.
  This makes the driver compatible with a wider range of system
  configurations.
- Updated ar0234_calculate_pll() to use a temporary structure and
  update cached PLL only on success.

Changes since v1:
- Improved error handling: use cci_write() with &ret chaining for
  sequential register writes, as suggested by Isaac Scott.
- Refactored format and cropping support:
  Replaced static format list with dynamic cropping rectangle
  (struct v4l2_rect crop).
  Implemented get_selection and set_selection for V4L2_SEL_TGT_CROP,
  allowing runtime selection of the active sensor area.
- Migrated to modern streaming model: replaced s_stream with
  enable_streams/disable_streams using v4l2_subdev_s_stream_helper.
- Corrected blanking constants: replaced ambiguous AR0234_HBLANK_DEF
  with AR0234_LINE_LENGTH_PCK_MIN; updated min/max ranges.
- Added ACPI match table (untested).
- Style fixes.

Any further comments or test results would be greatly appreciated.

Alexander Shiyan (2):
  dt-bindings: media: i2c: Add onsemi AR0234 image sensor binding
  media: i2c: Add onsemi AR0234 image sensor driver

 .../bindings/media/i2c/onnn,ar0234.yaml       |  109 ++
 drivers/media/i2c/Kconfig                     |   12 +
 drivers/media/i2c/Makefile                    |    1 +
 drivers/media/i2c/ar0234.c                    | 1309 +++++++++++++++++
 4 files changed, 1431 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/media/i2c/onnn,ar0234.yaml
 create mode 100644 drivers/media/i2c/ar0234.c

-- 
2.52.0