Mention the maximum voltages of the CEC and HPD lines. Since in the example these lines are connected to a Raspberry Pi and the Rpi GPIO lines are 3.3V it is a good idea to warn against directly connecting the HPD to the Raspberry Pi's GPIO line.
Signed-off-by: Hans Verkuil <hans.verk...@cisco.com> --- diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt index 46a0bac8b3b9..b36490aba7eb 100644 --- a/Documentation/devicetree/bindings/media/cec-gpio.txt +++ b/Documentation/devicetree/bindings/media/cec-gpio.txt @@ -4,6 +4,10 @@ The HDMI CEC GPIO module supports CEC implementations where the CEC line is hooked up to a pull-up GPIO line and - optionally - the HPD line is hooked up to another GPIO line. +Please note: the maximum voltage for the CEC line is 3.63V, for the HPD +line it is 5.3V. So you may need some sort of level conversion circuitry +when connecting them to a GPIO line. + Required properties: - compatible: value must be "cec-gpio". - cec-gpios: gpio that the CEC line is connected to. The line should be @@ -21,7 +25,7 @@ the following property is optional: 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: +connected to pin 11 aka BCM17 (some level shifter is needed for this!): #include <dt-bindings/gpio/gpio.h>
