Re: [PATCH v4 0/8] media: Introduce V4L2 extensible parameters

Hi Jacopo

On 20/08/2025 14:58, Jacopo Mondi wrote:

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/20250624-c55-v10-15-54f3d4196990@ideasonboard.com/

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

I'm currently working on another ISP driver: NXP neo, and also use 
extended params so as RkISP1.

Using common types looks like really interesting approach. However, only 
params are taken into account, while NXP neo also provides statistics. 
I'm currently testing extended approach for both params AND statistics. 
But v4l2-params only applies to .. params, as stated in the name.

Is there any plan to apply the same to statistics ?

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.

I have been able to test this on RkISP1 but not on C3.

Also tested on NXP neo locally.

Best regards
Antoine

Thanks
   j

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
---
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-validation-v3-0-9dc008348b30@ideasonboard.com (local)

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-validation-v2-0-7ec8918ec443@ideasonboard.com (local)

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-validation-v1-0-9fc27c9c728c@ideasonboard.com (local)

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

  Documentation/driver-api/media/v4l2-core.rst       |   1 +
  Documentation/driver-api/media/v4l2-params.rst     |   5 +
  .../media/v4l/extensible-parameters.rst            |  89 ++++++
  .../userspace-api/media/v4l/meta-formats.rst       |   1 +
  MAINTAINERS                                        |  10 +
  .../media/platform/amlogic/c3/isp/c3-isp-params.c  | 263 ++++++----------
  .../media/platform/rockchip/rkisp1/rkisp1-params.c | 349 +++++++++------------
  drivers/media/v4l2-core/Makefile                   |   3 +-
  drivers/media/v4l2-core/v4l2-params.c              | 126 ++++++++
  include/media/v4l2-params.h                        | 164 ++++++++++
  include/uapi/linux/media/amlogic/c3-isp-config.h   |  48 +--
  include/uapi/linux/media/v4l2-extensible-params.h  | 146 +++++++++
  include/uapi/linux/rkisp1-config.h                 |  67 ++--
  13 files changed, 817 insertions(+), 455 deletions(-)
---
base-commit: a75b8d198c55e9eb5feb6f6e155496305caba2dc
change-id: 20250701-extensible-parameters-validation-c831f7f5cc0b

Best regards,