Add support for CEC hardware that relies on low-level pin polling or
GPIO interrupts.
One example is the Allwinner SoC. But any GPIO-based CEC implementation can
use this as well.
A GPIO implementation is very suitable as well for debugging: it can use
interrupts to detect state changes and report it. Userspace can then verify
if the bus traffic is correct. This also makes error injection possible.
The disadvantage is that it is hard to get the timings right since linux
isn't a hard realtime system.
In general on an idle system it works quite well, but under load the timer
will miss its mark every so often.
The debugfs file /sys/kernel/debug/cec/cecX/status gives some statistics
with respect to the timer overruns.
When the adapter is unconfigured and the low-level driver supports
interrupts, then the interrupt will be used to detect changes. This should
be quite accurate. But when the adapter is configured a hrtimer has to be
used.
The hrtimer implements a state machine where for each state the code will
read the bus or drive the bus and go on to the next state. It will re-arm
the timer with a delay based on the next state.
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>
This config option is strictly speaking independent of the
media subsystem since it can be used by drm as well.
Besides, it looks odd when drivers select CEC_CORE and
MEDIA_CEC_NOTIFIER, that's inconsistent naming.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
The Kconfig options for the CEC subsystem were a bit messy. In
addition there were two cec sources (cec-edid.c and cec-notifier.c)
that were outside of the media/cec directory, which was weird.
Move those sources to media/cec as well.
The cec-edid and cec-notifier functionality is now part of the cec
module and these are no longer separate modules.
Also remove the MEDIA_CEC_EDID config option and include it with the
main CEC config option (which defined CEC_EDID anyway).
Added static inlines to cec-edid.h for dummy functions when CEC_CORE
isn't defined.
CEC drivers should now depend on CEC_CORE.
CEC drivers that need the cec-notifier functionality must explicitly
select CEC_NOTIFIER.
The s5p-cec and stih-cec drivers depended on VIDEO_DEV instead of
CEC_CORE, fix that as well.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
The last open issues have been addressed, so it is time to move
this out of staging and into the mainline and to move the public
cec headers to include/uapi/linux.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Hans Verkuil