Re: [PATCH 00/18] media: microchip-isc: Color correction and histogram stats

On Fri, Oct 10, 2025 at 09:21:51AM +0100, Kieran Bingham wrote:

Quoting Eugen Hristev (2025-10-09 21:11:17)

quoted

On 10/9/25 18:52, Balamanikandan Gunasundar wrote:

quoted

Hi,

This patch series has a set of enhancements to the Microchip Image Sensor
Controller driver. The objective is to expand its image processing
capabilities and to improve the colors.

This series also introduces a new stats driver that exposes the histogram
data to userspace via v4l2 controls. This allows applications such as
libcamera to access real time image statistics for advanced image
processing like automatic exposure, white balance adjustments etc.

How much data do you anticipate to be passing through controls? (What
can the hardware provide in total if we look at the bigger picture to
support the full device?)

For all other ISPs we've been working towards using structured parameter
buffers to pass data - and we've been making that format extensible,
which I think could also be a design that can apply to statistics.

This would greatly reduce the overhead of managing 'one control per
value' ... or things like passing large tables (like a lens shading
table perhaps) through controls.

V4L2 is standardizing on parameter buffers and statistics buffers for
ISPs. Using the same mechanism here will keep the driver in line with
other ISPs, which will help in userspace too.

quoted

quoted

Balakrishnan Sambath (11):
  media: microchip-isc: Enable GDC and CBC module flags for RGB formats
  media: microchip-isc: Improve histogram calculation with outlier
    rejection
  media: microchip-isc: Use channel averages for Grey World AWB
  media: microchip-isc: Add range based black level correction
  media: platform: microchip: Extend gamma table and control range
  media: platform: microchip: Add new histogram submodule
  media: microchip-isc: Register and unregister statistics device
  media: microchip-isc: Always enable histogram for all RAW formats
  media: microchip-isc: fix histogram state initialization order
  media: microchip-isc: decouple histogram cycling from AWB mode
  media: microchip-isc: enable userspace histogram statistics export

Balamanikandan Gunasundar (7):
  media: platform: microchip: set maximum resolution for sam9x7
  media: platform: microchip: Include DPC modules flags in pipeline
  media: microchip-isc: expose hue and saturation as v4l2 controls
  media: microchip-isc: Rename CBC to CBHS
  media: microchip-isc: Store histogram data of all channels
  media: videodev2.h, v4l2-ioctl: Add microchip statistics format
  media: microchip-isc: expose color correction registers as v4l2
    controls

 drivers/media/platform/microchip/Kconfig      |   2 +
 drivers/media/platform/microchip/Makefile     |   2 +-
 .../platform/microchip/microchip-isc-base.c   | 373 ++++++++++--
 .../platform/microchip/microchip-isc-regs.h   |   3 +
 .../platform/microchip/microchip-isc-stats.c  | 549 ++++++++++++++++++
 .../media/platform/microchip/microchip-isc.h  |  44 +-
 .../microchip/microchip-sama5d2-isc.c         |   2 +-
 .../microchip/microchip-sama7g5-isc.c         |  73 ++-
 drivers/media/v4l2-core/v4l2-ioctl.c          |   1 +
 include/linux/atmel-isc-media.h               |  13 +
 include/uapi/linux/videodev2.h                |   3 +
 11 files changed, 1001 insertions(+), 64 deletions(-)
 create mode 100644 drivers/media/platform/microchip/microchip-isc-stats.c

This looks interesting.
I would like to see the compliance tool output for more platforms
(sama7g5, sama5d2, and the new sam9x7), also the media-ctl -p , to see
the topology with your new driver.

-- 
Regards,

Laurent Pinchart