Linus Walleij writes:

On Mon, May 25, 2020 at 4:38 PM Lars Povlsen [off-list ref] wrote:

quoted

Yes, the problem is they're not in sequence. F.ex. you could have ports
0,1 enabled, skip 2,3,4 and have 5,6,7 enabled.

Just use disabled nodes.

That would look like this in my idea of a device tree:

pinctrl@nnn {
    gpio0: gpio@0 {
        compatible = "foo";
        status = "ok";
        ....
    };
    gpio1: gpio@1 {
        compatible = "foo";
        status = "ok";
        ....
    };
    gpio2: gpio@2 {
        compatible = "foo";
        status = "disabled";
        ....
    };
    gpio3: gpio@3 {
        compatible = "foo";
        status = "disabled";
        ....
    };
    gpio4: gpio@4 {
        compatible = "foo";
        status = "disabled";
        ....
    };
    gpio5: gpio@5 {
        compatible = "foo";
        status = "ok";
        ....
    };
    gpio6: gpio@6 {
        compatible = "foo";
        status = "ok";
        ....
    };
    gpio7: gpio@7 {
        compatible = "foo";
        status = "ok";
        ....
    };
};

It is common to use the status to enable/disable nodes like this.

In the Linux kernel is is possible to iterate over these subnodes and
check which ones are enabled and disabled while keeping the
index by using something like:

i = 0;
struct device_node *np, *child;
for_each_child_of_node(np, child) {
    if (of_device_is_available(child)) {
        pr_info("populating device %d\n", i);
    }
    i++;
}

Certainly you can use i in the above loop to populate your registers
etc from an indexed array.

This way the consumers can pick their GPIO from the right port
and everything just using e.g.
my-gpios = <&gpio6 4 GPIO_OUT_LOW>;

Linux, thank you for your input, it is much appreciated. I will use the
pattern in the driver in the next revision.

The only issue is that the gpios on the same "port" have restrictions on
their status - they can only be enabled "all" or "none" for gpios that
map to the same port. F.ex. gpio0, gpio32, gpio64 and gpio96 must all be
enabled or disabled because at the hardware level you control the
_port_. But as I noted earlier, that could just be the driver enforcing
this.

Thanks again.

---Lars

Yours,
Linus Walleij

-- 
Lars Povlsen,
Microchip

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