linux-kernel - [RFC v2 2/5] Documentation: media: Describe exposure and gain controls for multiple captures

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Message-ID: <20250818155809.469479-3-mirela.rabulea@nxp.com>
Date: Mon, 18 Aug 2025 18:58:06 +0300
From: Mirela Rabulea <mirela.rabulea@....com>
To: mchehab@...nel.org,
	sakari.ailus@...ux.intel.com,
	hverkuil-cisco@...all.nl,
	laurent.pinchart+renesas@...asonboard.com,
	ribalda@...omium.org,
	jai.luthra@...asonboard.com,
	laurentiu.palcu@....com
Cc: linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	LnxRevLi@....com,
	julien.vuillaumier@....com,
	celine.laurencin@....com
Subject: [RFC v2 2/5] Documentation: media: Describe exposure and gain controls for multiple captures

The standard controls for exposure and gains allow a
single value, for a single capture. For sensors with HDR
capabilities or context switching, this is not enough, so
add new controls that allow multiple values, one for each
capture.

Signed-off-by: Mirela Rabulea <mirela.rabulea@....com>
---

Changes in v2:
	Mention order inside array, from longest to shortest exposure
	Mention not to implement the -single controls if -multi controls are implemented

 .../media/v4l/ext-ctrls-image-source.rst      | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
index 71f23f131f97..2526d4d19cbb 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-source.rst
@@ -92,3 +92,24 @@ Image Source Control IDs
     representing a gain of exactly 1.0. For example, if this default value
     is reported as being (say) 128, then a value of 192 would represent
     a gain of exactly 1.5.
+
+``V4L2_CID_EXPOSURE_MULTI (__u32 array)``
+    Same as V4L2_CID_EXPOSURE, but for multiple exposure sensors. Each
+    element of the array holds the exposure value for one capture, from
+    the longest to the shortest exposure. Drivers for HDR sensors that
+    implement the V4L2_CID_EXPOSURE_MULTI control should not implement
+    V4L2_CID_EXPOSURE.
+
+``V4L2_CID_AGAIN_MULTI (__u32 array)``
+    Same as V4L2_CID_ANALOGUE_GAIN, but for multiple exposure sensors. Each
+    element of the array holds the analog gain value for one capture, from
+    the longest to the shortest exposure. Drivers for HDR sensors that
+    implement the V4L2_CID_AGAIN_MULTI control should not implement
+    V4L2_CID_ANALOGUE_GAIN.
+
+``V4L2_CID_DGAIN_MULTI (__u32 array)``
+    Same as V4L2_CID_DIGITAL_GAIN, but for multiple exposure sensors. Each
+    element of the array holds the digital gain value for one capture, from
+    the longest to the shortest exposure. Drivers for HDR sensors that
+    implement the V4L2_CID_DGAIN_MULTI control should not implement
+    V4L2_CID_DIGITAL_GAIN.
-- 
2.43.0