From: Hans Verkuil hans.verkuil@cisco.com
This driver adds support for CEC implementations that use a pull-up GPIO line. While SoCs exist that do this, the primary use-case is to turn a single-board computer into a cheap CEC debugger.
Together with 'cec-ctl --monitor-pin' you can do low-level CEC bus monitoring and do protocol analysis. And error injection is also planned for the future.
Here is an example using the Raspberry Pi 3:
https://hverkuil.home.xs4all.nl/rpi3-cec.jpg
While this example is for the Rpi, this driver will work for any SoC with a pull-up GPIO line.
In addition the cec-gpio driver can optionally monitor the HPD line. The state of the HPD line influences the CEC behavior so it is very useful to be able to monitor both.
And some HDMI sinks are known to quickly toggle the HPD when e.g. switching between inputs. So it is useful to be able to see an event when the HPD changes value.
The first two patches add support for the new HPD events. The last three patches are for the cec-gpio driver itself.
Regards,
Hans
Changes since v5:
- incorporated Linus Walleij's comments into the bindings document.
Changes since v4:
- cec-gpio.txt: *-gpio -> *-gpios - cec-gpio.txt: document hdmi-phandle. To be used when cec-gpio is associated with an HDMI receiver/transmitter. - cec-gpio.txt: remove incorrect @7 from dts example.
Changes since v3:
- cec-gpio.txt: refer to lines instead of pins and use OPEN_DRAIN in the example. - Kconfig: add select GPIOLIB - cec-gpio.c: switch to gpiod. - cec-core.c: initialize the devnode mutex/list in allocate_adapter. Doing this in register_adapter is too late if the HPD is high.
Changes since v2:
- Add support for HPD events. - Switch from pin BCM4 to pin BCM7 in the bindings example
Changes since v1:
- Updated the bindings doc to not refer to the driver, instead refer to the hardware.
Hans Verkuil (5): cec: add CEC_EVENT_PIN_HPD_LOW/HIGH events cec-ioc-dqevent.rst: document new CEC_EVENT_PIN_HPD_LOW/HIGH events dt-bindings: document the CEC GPIO bindings cec-gpio: add HDMI CEC GPIO driver MAINTAINERS: add cec-gpio entry
.../devicetree/bindings/media/cec-gpio.txt | 32 +++ Documentation/media/uapi/cec/cec-ioc-dqevent.rst | 18 ++ MAINTAINERS | 9 + drivers/media/cec/cec-adap.c | 18 +- drivers/media/cec/cec-api.c | 18 +- drivers/media/cec/cec-core.c | 8 +- drivers/media/platform/Kconfig | 10 + drivers/media/platform/Makefile | 2 + drivers/media/platform/cec-gpio/Makefile | 1 + drivers/media/platform/cec-gpio/cec-gpio.c | 236 +++++++++++++++++++++ include/media/cec-pin.h | 4 + include/media/cec.h | 12 +- include/uapi/linux/cec.h | 2 + 13 files changed, 360 insertions(+), 10 deletions(-) create mode 100644 Documentation/devicetree/bindings/media/cec-gpio.txt create mode 100644 drivers/media/platform/cec-gpio/Makefile create mode 100644 drivers/media/platform/cec-gpio/cec-gpio.c