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media: cec-core.rst: include cec-pin.h and cec-notifier.h 

Include the CEC pin framework documentation by reading cec-pin.h.
Include the CEC notifier framework documentation by reading cec-notifier.h.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
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Hans Verkuil 2017-07-11 03:30:43 -03:00 committed by Mauro Carvalho Chehab
parent ea5c8ef296
commit ab2ec7a53c
1 changed files with 31 additions and 0 deletions
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Documentation/media/kapi/cec-core.rst
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@ -345,3 +345,34 @@ log_addrs->num_log_addrs set to 0. The block argument is ignored when
unconfiguring. This function will just return if the physical address is
invalid. Once the physical address becomes valid, then the framework will
attempt to claim these logical addresses.
CEC Pin framework
-----------------
Most CEC hardware operates on full CEC messages where the software provides
the message and the hardware handles the low-level CEC protocol. But some
hardware only drives the CEC pin and software has to handle the low-level
CEC protocol. The CEC pin framework was created to handle such devices.
Note that due to the close-to-realtime requirements it can never be guaranteed
to work 100%. This framework uses highres timers internally, but if a
timer goes off too late by more than 300 microseconds wrong results can
occur. In reality it appears to be fairly reliable.
One advantage of this low-level implementation is that it can be used as
a cheap CEC analyser, especially if interrupts can be used to detect
CEC pin transitions from low to high or vice versa.
.. kernel-doc:: include/media/cec-pin.h
CEC Notifier framework
-----------------
Most drm HDMI implementations have an integrated CEC implementation and no
notifier support is needed. But some have independent CEC implementations
that have their own driver. This could be an IP block for an SoC or a
completely separate chip that deals with the CEC pin. For those cases a
drm driver can install a notifier and use the notifier to inform the
CEC driver about changes in the physical address.
.. kernel-doc:: include/media/cec-notifier.h