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Diffstat (limited to 'Documentation/driver-api/media/tx-rx.rst')
| -rw-r--r-- | Documentation/driver-api/media/tx-rx.rst | 25 |
1 files changed, 13 insertions, 12 deletions
diff --git a/Documentation/driver-api/media/tx-rx.rst b/Documentation/driver-api/media/tx-rx.rst index e1e9258dd862..29d66a47b56e 100644 --- a/Documentation/driver-api/media/tx-rx.rst +++ b/Documentation/driver-api/media/tx-rx.rst @@ -6,8 +6,8 @@ Pixel data transmitter and receiver drivers =========================================== V4L2 supports various devices that transmit and receive pixel data. Examples of -these devices include a camera sensor, a TV tuner and a parallel or a CSI-2 -receiver in an SoC. +these devices include a camera sensor, a TV tuner and a parallel, a BT.656 or a +CSI-2 receiver in an SoC. Bus types --------- @@ -22,12 +22,13 @@ the host SoC. It is defined by the `MIPI alliance`_. .. _`MIPI alliance`: https://www.mipi.org/ -Parallel -^^^^^^^^ +Parallel and BT.656 +^^^^^^^^^^^^^^^^^^^ -`BT.601`_ and `BT.656`_ are the most common parallel busses. +The parallel and `BT.656`_ buses transport one bit of data on each clock cycle +per data line. The parallel bus uses synchronisation and other additional +signals whereas BT.656 embeds synchronisation. -.. _`BT.601`: https://en.wikipedia.org/wiki/Rec._601 .. _`BT.656`: https://en.wikipedia.org/wiki/ITU-R_BT.656 Transmitter drivers @@ -90,8 +91,8 @@ where pixel rate on the camera sensor's pixel array which is indicated by the :ref:`V4L2_CID_PIXEL_RATE <v4l2-cid-pixel-rate>` control. -LP-11 and LP-111 modes -^^^^^^^^^^^^^^^^^^^^^^ +LP-11 and LP-111 states +^^^^^^^^^^^^^^^^^^^^^^^ As part of transitioning to high speed mode, a CSI-2 transmitter typically briefly sets the bus to LP-11 or LP-111 state, depending on the PHY. This period @@ -105,7 +106,7 @@ in software, especially when there is no interrupt telling something is happening. One way to address this is to configure the transmitter side explicitly to LP-11 -or LP-111 mode, which requires support from the transmitter hardware. This is +or LP-111 state, which requires support from the transmitter hardware. This is not universally available. Many devices return to this state once streaming is stopped while the state after power-on is LP-00 or LP-000. @@ -116,11 +117,11 @@ transitioning to streaming state, but not yet start streaming. Similarly, the to call ``.post_streamoff()`` for each successful call of ``.pre_streamon()``. In the context of CSI-2, the ``.pre_streamon()`` callback is used to transition -the transmitter to the LP-11 or LP-111 mode. This also requires powering on the +the transmitter to the LP-11 or LP-111 state. This also requires powering on the device, so this should be only done when it is needed. -Receiver drivers that do not need explicit LP-11 or LP-111 mode setup are waived -from calling the two callbacks. +Receiver drivers that do not need explicit LP-11 or LP-111 state setup are +waived from calling the two callbacks. Stopping the transmitter ^^^^^^^^^^^^^^^^^^^^^^^^ |