media: Introduce V4L2 generic ISP support

Extensible parameters meta formats have been introduced in the Linux
kernel v6.12 initially to support different revision of the RkISP1 ISP
implemented in different SoC. In order to avoid breaking userspace
everytime an ISP configuration block is added or modified in the uAPI
these new formats, which are versionated and extensible by their
definition have been introduced.

See for reference:
e9d05e9d5db1 ("media: uapi: rkisp1-config: Add extensible params format")
6c53a7b68c5d ("media: rkisp1: Implement extensible params support")

The Amlogic C3 ISP driver followed shortly, introducing an extensible
format for the ISP configuration:

6d406187ebc0 ("media: uapi: Add stats info and parameters buffer for C3 ISP")

with a very similar, if not identical, implementation of the routines to
validate and handle the ISP configuration in the ISP driver in the
c3-isp-params.c file.

fb2e135208f3 ("media: platform: Add C3 ISP driver")

With the recent upstreaming attempt of the Mali C55 ISP driver from Dan,
a third user of extensible parameters is going to be itroduced in the
kernel, duplicating again in the driver the procedure for validating and
handling the ISP configuration blocks

https://patchwork.linuxtv.org/project/linux-media/patch/2...

To avoid duplicating again the validation routines and common types
definition, this series introduces v4l2-isp.c/.h for the kAPI
and v4l2-isp.h for the uAPI and re-organize the RkISP1
and Amlogic C3 drivers to use the common types and the helper validation
routines.

The v4l2-isp abstraction will be augmented to support statistcs as well.

If the here proposed approach is accepted, I propose to rebase the Mali
C55 driver on top of this series, to use the new common types and
helpers.

Tested on Mali C55 and RkISP1 with camshark

Thanks
  j

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
Changes in v7:
- Moved version to the v4l2-isp uAPI
- Moved version check to the v4l2-isp.c helpers
- Link to v6: https://lore.kernel.org/r/20251007-extensible-parameters-...

Changes in v6:
- Rename all symbols to v4l2_isp
- Changed the interface of the two buffer validation functions
- Reworked the rkisp1 and c3 porting accordingly
- Updated documentation
- I have moved v4l2_params_buffer_size() from uAPI because it was
  convenient for linux but not required in userspace
- Link to v5: https://lore.kernel.org/r/20250915-extensible-parameters-...

Changes in v5:
- Move everything to v4l2-isp prefix except from format documentation
  which still is about 'extensible-parameters' (to be paired in future
  with extensbile-stats)
- Simplify documentation and move it part to the driver-api
  Documentation
- Remove 'group' and 'features' from the generic handlers definition and
  adjust rkisp1 accordingly
- Link to v4: https://lore.kernel.org/r/20250820-extensible-parameters-...

Changes in v4:
- Fix the definition of V4L2_PARAMS_FL_PLATFORM_FLAGS
- Add __counted_by() attribute to the data[] flexible-array member of
  v4l2_params_buffer
- Minor style change
- Link to v3: https://lore.kernel.org/r/20250819-extensible-parameters-...

Changes in v3:
- Rebased on latest media-committers/next
- Take in Dan's suggestion in block size validation
- Documentation minor spelling fixes
- Link to v2: https://lore.kernel.org/r/20250710-extensible-parameters-...

Changes in v2:
- Make v4l2_params_buffer directly usable
- Centralize ENABLE/DISABLE flags definition and validation
- Take in Dan's v4l2_params_buffer_size()
- Allow blocks to only contain the header if they're going to be
  disabled
- Documentation fixes as reported by Nicolas
- Link to v1: https://lore.kernel.org/r/20250708-extensible-parameters-...

---
Jacopo Mondi (8):
      media: uapi: Introduce V4L2 generic ISP types
      media: uapi: Convert RkISP1 to V4L2 extensible params
      media: uapi: Convert Amlogic C3 to V4L2 extensible params
      media: Documentation: uapi: Add V4L2 ISP documentation
      media: v4l2-core: Introduce v4l2-isp.c
      media: rkisp1: Use v4l2-isp for validation
      media: amlogic-c3: Use v4l2-isp for validation
      media: Documentation: kapi: Add v4l2 generic ISP support

 Documentation/driver-api/media/v4l2-core.rst       |   1 +
 Documentation/driver-api/media/v4l2-isp.rst        |  49 ++++++
 .../userspace-api/media/v4l/meta-formats.rst       |   1 +
 Documentation/userspace-api/media/v4l/v4l2-isp.rst | 121 ++++++++++++++
 MAINTAINERS                                        |  10 ++
 drivers/media/platform/amlogic/c3/isp/Kconfig      |   1 +
 .../media/platform/amlogic/c3/isp/c3-isp-params.c  | 124 +++-----------
 drivers/media/platform/rockchip/rkisp1/Kconfig     |   1 +
 .../media/platform/rockchip/rkisp1/rkisp1-params.c | 183 +++++++++------------
 drivers/media/v4l2-core/Kconfig                    |   4 +
 drivers/media/v4l2-core/Makefile                   |   1 +
 drivers/media/v4l2-core/v4l2-isp.c                 | 128 ++++++++++++++
 include/media/v4l2-isp.h                           |  91 ++++++++++
 include/uapi/linux/media/amlogic/c3-isp-config.h   |  92 +++--------
 include/uapi/linux/media/v4l2-isp.h                | 102 ++++++++++++
 include/uapi/linux/rkisp1-config.h                 | 107 +++---------
 16 files changed, 660 insertions(+), 356 deletions(-)
---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20250701-extensible-parameters-validation-c831f7f5cc0b

Best regards,
-- 
Jacopo Mondi <jacopo.mondi@ideasonboard.com>