On Wed, Aug 30, 2017 at 6:10 PM, Hans Verkuil hverkuil@xs4all.nl wrote:
From: Hans Verkuil hans.verkuil@cisco.com
Document the bindings for the cec-gpio module for hardware where the CEC pin and optionally the HPD pin are connected to GPIO pins.
Signed-off-by: Hans Verkuil hans.verkuil@cisco.com
I usually refer to GPIO "lines" rather than "pins" for clarity. It's because some systems also have pin control, and then it becomes a bit muddy what is a pin.
+* HDMI CEC GPIO driver
+The HDMI CEC GPIO module supports CEC implementations where the CEC pin +is hooked up to a pull-up GPIO pin and - optionally - the HPD pin is +hooked up to a pull-down GPIO pin.
+Required properties:
- compatible: value must be "cec-gpio"
- cec-gpio: gpio that the CEC line is connected to
+Optional property:
- hpd-gpio: gpio that the HPD line is connected to
+Example for the Raspberry Pi 3 where the CEC line is connected to +pin 26 aka BCM7 aka CE1 on the GPIO pin header and the HPD line is +connected to pin 11 aka BCM17:
+cec-gpio@7 {
compatible = "cec-gpio";cec-gpio = <&gpio 7 GPIO_ACTIVE_HIGH>;hpd-gpio = <&gpio 17 GPIO_ACTIVE_HIGH>;+};
So what I understood from the driver is that the cec-gpio is maybe actually an open drain output line, so in that case it should be stated in the docs and cec-gpio = <&gpio 7 GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN> or GPIO_LINE_OPEN_DRAIN if it is not also single-ended.
Yours, Linus Walleij