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

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Message-ID: <843d646a-a720-4431-b9cb-5a0a9bdc9d59@kernel.org>
Date: Mon, 10 Nov 2025 10:01:21 +0100
From: Hans Verkuil <hverkuil+cisco@...nel.org>
To: Balamanikandan Gunasundar <balamanikandan.gunasundar@...rochip.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: Eugen Hristev <eugen.hristev@...aro.org>, Chas Williams
 <3chas3@...il.com>, Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Claudiu Beznea <claudiu.beznea@...on.dev>,
 Balakrishnan Sambath <balakrishnan.s@...rochip.com>,
 Hans Verkuil <hverkuil@...nel.org>, Ricardo Ribalda <ribalda@...omium.org>,
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
 Jacopo Mondi <jacopo.mondi@...asonboard.com>,
 Daniel Scally <dan.scally+renesas@...asonboard.com>,
 Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linux-atm-general@...ts.sourceforge.net, netdev@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 00/18] media: microchip-isc: Color correction and
 histogram stats

Hi Balamanikandan,

On 09/10/2025 17:52, Balamanikandan Gunasundar wrote:
> 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.

Most of this series is fine, but the histogram part needs more work.

I would recommend splitting up this series in two parts: one for the
various fixes and improvements, and one for the histogram feature.

The first series with the fixes I can take easily. In fact, if you
post that this week (no later than Thursday), then I can pick it
up in time for v6.19.

As mentioned the histogram part needs more work. Mostly small stuff,
but the documentation is the major missing part.

I also want to see the output of 'v4l2-compliance -m0 -s' (i.e.
with streaming) in the cover letter of the histogram series to be
certain nothing was forgotten.

Make sure you compile v4l2-compliance straight from the git repo,
don't use a distro version since that's usually out of date.

Regards,

	Hans

> 
> 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
>