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authorSakari Ailus <sakari.ailus@linux.intel.com>2020-10-13 17:02:27 +0300
committerMauro Carvalho Chehab <mchehab+huawei@kernel.org>2020-11-16 12:31:15 +0300
commit9d0a79e55a626165efb52bb15d714d231fc985e6 (patch)
tree1d4b981927ae56cdff88dccde01b799d34430d0d /Documentation/driver-api
parentd3ed195bc761a1c5e5f1feae519318a4f91d258c (diff)
downloadlinux-9d0a79e55a626165efb52bb15d714d231fc985e6.tar.xz
media: Documentation: v4l: Document required controls on camera sensors
Raw camera sensors connected to parallel or CSI-2 busses need to implement V4L2_CID_LINK_FREQ control so receiver drivers can configure the hardware accordingly. Document this. Also say V4L2_CID_PIXEL_RATE is recommended for such hardware. Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Diffstat (limited to 'Documentation/driver-api')
-rw-r--r--Documentation/driver-api/media/camera-sensor.rst13
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst
index 4d1ae12b9b4d..ffb0cad8137a 100644
--- a/Documentation/driver-api/media/camera-sensor.rst
+++ b/Documentation/driver-api/media/camera-sensor.rst
@@ -132,3 +132,16 @@ used to obtain device's power state after the power state transition:
The function returns a non-zero value if it succeeded getting the power count or
runtime PM was disabled, in either of which cases the driver may proceed to
access the device.
+
+Controls
+--------
+
+For camera sensors that are connected to a bus where transmitter and receiver
+require common configuration set by drivers, such as CSI-2 or parallel (BT.601
+or BT.656) bus, the ``V4L2_CID_LINK_FREQ`` control is mandatory on transmitter
+drivers. Receiver drivers can use the ``V4L2_CID_LINK_FREQ`` to query the
+frequency used on the bus.
+
+The transmitter drivers should also implement ``V4L2_CID_PIXEL_RATE`` control in
+order to tell the maximum pixel rate to the receiver. This is required on raw
+camera sensors.