linux-kernel - [PATCH v5 8/8] media: Documentation: kapi: Add v4l2 generic ISP support

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Message-Id: <20250915-extensible-parameters-validation-v5-8-e6db94468af3@ideasonboard.com>
Date: Mon, 15 Sep 2025 19:18:17 +0200
From: Jacopo Mondi <jacopo.mondi@...asonboard.com>
To: Dafna Hirschfeld <dafna@...tmail.com>, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Keke Li <keke.li@...ogic.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Heiko Stuebner <heiko@...ech.de>, Dan Scally <dan.scally@...asonboard.com>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Antoine Bouyer <antoine.bouyer@....com>
Cc: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
 linux-rockchip@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
 Jacopo Mondi <jacopo.mondi@...asonboard.com>
Subject: [PATCH v5 8/8] media: Documentation: kapi: Add v4l2 generic ISP
 support

Add to the driver-api documentation the v4l2-isp.h types and
helpers documentation.

Reviewed-by: Daniel Scally <dan.scally@...asonboard.com>
Signed-off-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>
---
 Documentation/driver-api/media/v4l2-core.rst |  1 +
 Documentation/driver-api/media/v4l2-isp.rst  | 37 ++++++++++++++++++++++++++++
 MAINTAINERS                                  |  1 +
 3 files changed, 39 insertions(+)

diff --git a/Documentation/driver-api/media/v4l2-core.rst b/Documentation/driver-api/media/v4l2-core.rst
index ad987c34ad2a8460bb95e97adc4d850d624e0b81..a5f5102c64cca57b57b54ab95882b26286fb27de 100644
--- a/Documentation/driver-api/media/v4l2-core.rst
+++ b/Documentation/driver-api/media/v4l2-core.rst
@@ -27,3 +27,4 @@ Video4Linux devices
     v4l2-common
     v4l2-tveeprom
     v4l2-jpeg
+    v4l2-isp
diff --git a/Documentation/driver-api/media/v4l2-isp.rst b/Documentation/driver-api/media/v4l2-isp.rst
new file mode 100644
index 0000000000000000000000000000000000000000..d778aa799347bfd0a95bd6887dd944ddad0fe4d1
--- /dev/null
+++ b/Documentation/driver-api/media/v4l2-isp.rst
@@ -0,0 +1,37 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+V4L2 generic ISP parameters and statistics support
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+ISP configuration parameters and statistics are processed and collected by
+drivers and exchanged with userspace through data types that usually
+reflect the ISP peripheral registers layout.
+
+Each ISP driver defines its own metadata format for parameters and statistics,
+and exposing the registers layout in the format definition, part of the Linux
+kernel uAPI/uABI interface, makes it really hard, if not impossible, to extend
+the format in a backward compatible way to support new hardware blocks or
+different revisions of the same peripheral IP.
+
+For these reasons Video4Linux2 defines generic types for ISP configuration
+parameters and statistics with a set of associated helpers to support drivers
+and users using generic types.
+
+Generic ISP configuration parameters
+====================================
+
+Drivers can use the generic and extensible configuration parameters format by
+re-using the types defined in the include/uapi/linux/media/v4l2-isp.h uAPI
+header file.
+
+The uAPI header defines generic types which the driver is expected to re-use and
+provide definitions for the types of supported ISP blocks, their control
+flags and the expected maximum size of a buffer of parameters.
+
+When a driver receives a buffer of parameters from userspace it shall validate
+it by using the helper functions and types available in include/media/v4l2-isp.h
+before accessing the buffer to apply the parameters to the hardware registers.
+
+Generic ISP support driver documentation
+========================================
+.. kernel-doc:: include/media/v4l2-isp.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 5e0e4208ebe6c58a9ea0834e1ebb36abd2de06e1..b0c5e6c2b21a5d5ebc63d2ae8b5c1b68fa912b33 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26414,6 +26414,7 @@ V4L2 GENERIC ISP PARAMETERS AND STATISTIC FORMATS
 M:	Jacopo Mondi <jacopo.mondi@...asonboard.com>
 L:	linux-media@...r.kernel.org
 S:	Maintained
+F:	Documentation/driver-api/media/v4l2-isp.rst
 F:	Documentation/userspace-api/media/v4l/extensible-parameters.rst
 F:	drivers/media/v4l2-core/v4l2-isp.c
 F:	include/media/v4l2-isp.h

-- 
2.51.0