Re: Right amount of info in the DT

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Tue, May 30, 2017 at 3:59 PM, Yves Lefloch
<YvesMarie_Lefloch@xxxxxxxxxxxxxxxx> wrote:

> I've put together a draft to try and solve this problem using approach (A).
> Each IP node gets a GPIO child node, since this is what the hardware looks like,
> and they are all tied together using phandles to a central pin controller node.

I like the looks of this!

> The draft only demonstrates the solution for the pins dedicated to GPIO,
> namely `gpio_sys', and for the smartcard pins, namely `gpio_smcard'.

It is elegant and it will scale.

> As before, bindings are not yet commented.
>
> BTW, I'm sure there is a far better way than this `all_pins' array, let me know
> if you have feedback on that.

So that is this:

> +static const unsigned int all_pins[] = {
> +       0,  1,  2,  3,  4,  5,  6,  7,  8,  9,
> +       10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
> +       20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
> +       30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
> +       40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
> +       50, 51, 52, 53, 54, 55, 56, 57, 58, 59,
> +       60, 61, 62, 63, 64, 65, 66, 67, 68, 69,
> +       70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
> +       80, 81, 82, 83, 84, 85, 86, 87, 88, 89,
> +       90, 91, 92, 93, 94, 95, 96, 97, 98, 99,
> +};

That looks a bit like what we usually put in pin descriptors.

(...)

This:

> +       struct pinctrl_gpio_range *prange;
> +
(...)
> +       prange->name = group->label;
> +       prange->id = group->base;
> +       prange->base = group->base;
> +       prange->pin_base = group->base;
> +       prange->npins = group->ngpio;
> +       prange->gc = gchip;
> +       pinctrl_add_gpio_range(pindev, prange);

Can't you just add that to the device tree using the gpio-ranges
property? It is handled in the core and should "just work".

The documentation for that is a bit terse in
Documentation/devicetree/bindings/gpio/gpio.txt
but if you just grep for gpio-ranges you will get the hang of it.

It is handled from the gpiochip side which is advisible, even if
you hardcode it in the driver.

Yours,
Linus Walleij
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