GPIO implementation Bananapi m2 ultra

[mcabal...@gmail.com]

Hi all, this is my first post, I have a question about dts implementation for my BananaPi m2 ultra. I was looking for hints in previous posts, and other places, with no luck. Sorry if it´s a begginer question.

I´m trying to modify my dts file to add support for GPIO (no through gpio-leds, direct GPIO support). My scenario is:

HW: BananaPi-m2-ultra

O.S.: Armbian.

kernel version: 4.19.36-sunxi

I added a child node to the standard pinctrl descrpition:

    pio: pinctrl@1c20800 {

               compatible = "allwinner,sun8i-r40-pinctrl";

               reg = <0x1c20800 0x400>;

               interrupts = <0x0 0x1c 0x4>;

               clocks = <0x7 0x4f 0x2 0x4>;

               clock-names = "apb", "hosc", "losc";

               gpio-controller;

               interrupt-controller;

               #interrupt-cells = <0x3>;

               #gpio-cells = <0x3>;

               pinctrl-names = "default";

               pinctrl-0 = <0x13>;

               phandle = >0xd>;

               clk-out-a-pin {

                   pins = "PI12";

                   function = "clk_out_a";

                   drive = <0x0>;

                   pull = <0x0>;

                   phandle = <0x13>;

               };

               /* A lot of child node */

               /* My child node */

               myCustomOutput {

                   allwinner,pins = "PH3";

                   allwinner,function = "myOutput";

                   allwinner,drive = "1"; /* 20mA capable output */

               };

           }; /* End of pio */

So, when I want to implement the client node for myCustomOutputs I don't figure what the value for compatible property must to be.

At root level, I want to write:

    myOutput {

        compatible = "?????"; /* What value must be here */

        gpios = <0x7 0x3 GPIO_ACTIVE_HIGH>;

    };

Could please somebody point me in the right direction?    

Thanks in advance!

Mariano

[Ondřej Jirman]

Hi,

On Fri, May 03, 2019 at 09:41:23AM -0700, mcabal...@gmail.com wrote:
> Hi all, this is my first post, I have a question about dts implementation
> for my BananaPi m2 ultra. I was looking for hints in previous posts, and
> other places, with no luck. Sorry if it´s a begginer question.
>
> I´m trying to modify my dts file to add support for GPIO (no through
> gpio-leds, direct GPIO support). My scenario is:

It's not clear if you want to use GPIO from userspace or from the kernel.

Here's some info on how to access GPIO from userspace:

http://linux-sunxi.org/GPIO

regards,
o.

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[MH C]

Hi Ondřej, many thanks for your reply. You are right, I was not clear enough.

My final aim is to write an own driver to manage 4 GPIO inputs + 4 GPIO outputs in a very specific way (including interrupt in falling edge of inputs), so in the end of the road, I´m thinking about to access these pins from the user space, but through my own char device driver, so I will work in kernel and user spaces.

It´s my first time with an embedded running over an O.S. so I thought it would be a good idea to play for a while with GPIOs before to face the big problem.

I will check documentation that you suggested me.

One more time, thank you very much.

--

Mariano H. Caballero