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authorHans Verkuil <hans.verkuil@cisco.com>2017-07-11 09:30:42 +0300
committerMauro Carvalho Chehab <mchehab@s-opensource.com>2017-07-18 18:57:18 +0300
commitea5c8ef296681b53480ebeeffd06083bb60e693d (patch)
tree672a2ad5ce04c93d6e5a6afff7eeb290147bf3f1 /drivers/media/Kconfig
parentb8d62f50b1df2571afcf47107bbbe9cd60f8aafd (diff)
downloadlinux-ea5c8ef296681b53480ebeeffd06083bb60e693d.tar.xz
media: cec-pin: add low-level pin hardware support
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>
Diffstat (limited to 'drivers/media/Kconfig')
-rw-r--r--drivers/media/Kconfig3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/media/Kconfig b/drivers/media/Kconfig
index 55d9c2b82b7e..94d4e7759127 100644
--- a/drivers/media/Kconfig
+++ b/drivers/media/Kconfig
@@ -8,6 +8,9 @@ config CEC_CORE
config CEC_NOTIFIER
bool
+config CEC_PIN
+ bool
+
menuconfig MEDIA_SUPPORT
tristate "Multimedia support"
depends on HAS_IOMEM