Am Dienstag, den 18.10.2016, 18:02 +0300 schrieb Sakari Ailus: > Document the interface between the CSI-2 transmitter and receiver drivers. > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > --- > Hi folks, > > We've got multiple CSI-2 tranmitter and receiver drivers currently in the > kernel. Some receivers require information on dynamic bus parameters and > some of the transmitter drivers implement that. It's time to document what > is expected of both so we will not end up with multiple non-interoperable > implementations. > > Regards, > Sakari > > Documentation/media/kapi/csi2.rst | 35 +++++++++++++++++++++++++++++++++++ > Documentation/media/media_kapi.rst | 1 + > 2 files changed, 36 insertions(+) > create mode 100644 Documentation/media/kapi/csi2.rst > > diff --git a/Documentation/media/kapi/csi2.rst b/Documentation/media/kapi/csi2.rst > new file mode 100644 > index 0000000..856a509 > --- /dev/null > +++ b/Documentation/media/kapi/csi2.rst > @@ -0,0 +1,35 @@ > +MIPI CSI-2 > +========== > + > +CSI-2 is a data bus intended for transferring images from cameras to > +the host SoC. It is defined by the `MIPI alliance`_. > + > +.. _`MIPI alliance`: http://www.mipi.org/ > + > +Transmitter drivers > +------------------- > + > +CSI-2 transmitter, such as a sensor or a TV tuner, drivers need to > +provide the CSI-2 receiver with information on the CSI-2 bus > +configuration. These include the V4L2_CID_LINK_FREQ control and > +(:c:type:`v4l2_subdev_video_ops`->s_stream() callback). Both must be > +present on the sub-device represents the CSI-2 transmitter. The > +V4L2_CID_LINK_FREQ control is used to tell the receiver driver the > +frequency (and not the symbol rate) of the link and the > +:c:type:`v4l2_subdev_video_ops`->s_stream() callback provides an > +ability to start and stop the stream. > + > +The transmitter drivers must configure the CSI-2 transmitter to *LP-11 > +mode* whenever the transmitter is powered on but not active. Some > +transmitters do this automatically but some have to be explicitly > +programmed to do so. > + > +Receiver drivers > +---------------- > + > +Before the receiver driver may enable the CSI-2 transmitter by using > +the :c:type:`v4l2_subdev_video_ops`->s_stream(), it must have powered > +the transmitter up by using the > +:c:type:`v4l2_subdev_core_ops`->s_power() callback. This may take > +place either indirectly by using :c:func:`v4l2_pipeline_pm_use` or > +directly. > diff --git a/Documentation/media/media_kapi.rst b/Documentation/media/media_kapi.rst > index f282ca2..bc06389 100644 > --- a/Documentation/media/media_kapi.rst > +++ b/Documentation/media/media_kapi.rst > @@ -33,3 +33,4 @@ For more details see the file COPYING in the source distribution of Linux. > kapi/rc-core > kapi/mc-core > kapi/cec-core > + kapi/csi2 Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> so far. Should this document also include a suggestion on how exactly to calculate the number of lanes to use from the pixel rate and link frequency? regards Philipp -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
