topic Re: imx8 linux gpio-keys using gpio interrupt example in i.MX Processors

imx8 linux gpio-keys using gpio interrupt example

flobro — Wed, 20 Sep 2023 13:14:27 GMT

I would like to use a GPIO on the IMX8M plus as an input for the Linux gpio-keys driver. I have not been able to find any examples of the device tree entries required to enable the interrupts for a GPIO input bit to act as a "keypress".

Re: imx8 linux gpio-keys using gpio interrupt example

Chavira — Wed, 20 Sep 2023 18:51:49 GMT

Hi @flobro!

Thank you for contacting NXP Support!

For our boards, we don´t have examples, but you can see the documentation of the kernel following the link:

https://github.com/nxp-imx/linux-imx/blob/lf-6.1.y/Documentation/devicetree/bindings/gpio/gpio.txt

https://github.com/nxp-imx/linux-imx/blob/lf-6.1.y/Documentation/devicetree/bindings/gpio/fsl-imx-gpio.yaml

Best Regards!

Chavira

Re: imx8 linux gpio-keys using gpio interrupt example

flobro — Mon, 25 Sep 2023 14:14:33 GMT

Thanks for the response. I found out that there is GPIO support (gpio-mxc.c) that appears to handle the GPIO setup for interrupts properly, so I get a event from the "gpio-keys" config I set up in the device tree.

The only issue (not) is that there is more than just one or more bytes that get sent as an event. Good thing all I care about is that there is an event after the gpio changes state (vary rarely) which allow a blocking read to monitor it.

Re: imx8 linux gpio-keys using gpio interrupt example

Marco_Savo — Thu, 15 Feb 2024 12:23:10 GMT

Hello, the same, I can see

gpio_keys

Don't work on the board imx8, can you share your configuration?

Re: imx8 linux gpio-keys using gpio interrupt example

flobro — Thu, 15 Feb 2024 14:28:18 GMT

There are a few web pages that talk about setting up the device tree for gpio-keys:

https://www.kernel.org/doc/Documentation/devicetree/bindings/input/gpio-keys.txt

https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/18842398/Linux+GPIO+Driver?view=blog#LinuxGPIODriver-GPIO-KeysDriver

You have to modify the GPIO pin information to match your board design. This allows your GPIO to send a "key code" to an input driver (/dev/input/event0) that works kind of like an interrupt if a program does a blocking read on the input.