On 06/26/2013 05:42 AM, Christian Ruppert wrote:

On Wed, Jun 19, 2013 at 12:15:13PM -0600, Stephen Warren wrote:

quoted

On 06/19/2013 06:03 AM, Linus Walleij wrote:

quoted

On Tue, Jun 18, 2013 at 11:29 AM, Christian Ruppert
[off-list ref] wrote:

quoted

This patch adds the infrastructure required to register non-linear gpio
ranges through gpiolib and the standard GPIO device tree bindings.

Signed-off-by: Christian Ruppert <redacted>

I'm basically fine with this, but would like Stephen's ACK if possible.

quoted

+In addition, named groups of pins can be mapped to pin groups of a given
+pin controller:
+
+       gpio_pio_g: gpio-controller@1480 {
+               #gpio-cells = <2>;
+               compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
+               reg = <0x1480 0x18>;
+               gpio-controller;
+               gpio-ranges = <&pinctrl1 0 0 0>, <&pinctrl2 3 0 0>;
+               gpio-ranges-group-names = "foo", "bar";
+       };
+
+where,
+   &pinctrl1 and &pinctrl2 is the phandle to the pinctrl DT node.
+
+   The following value specifies the base GPIO offset of the pin range with
+   respect to the GPIO controller's base. The remaining two values must be
+   0 to indicate that a named pin group should be used for the respective
+   range. The number of pins in the range is the number of pins in the pin
+   group.

So while this works, these zeroes seem a bit awkward, but maybe
it's the only way?

I'm not good enough on device tree conventions, but isn't this possible:

              gpio-ranges = <&pinctrl1 0>, <&pinctrl2 3>;
              gpio-ranges-group-names = "foo", "bar";

Since we don't have any #gpio-ranges-cells or anything like that I
guess we can define this to have a flexible number of cells
depending on use case?

If we're willing to have gpio-ranges be either *all* group names, or
*all* IDs, we can define the format of gpio-ranges to have two cells
(phandle and GPIO number) if the property gpio-ranges-group-names
exists, but four cells (phandle, GPIO number, pin number, count)
otherwise. However, that's a little restrictive, since then what if one
GPIO controller is hooked to two different pinmux controllers, and you
want to use different formats for the references to each. A
#gpio-ranges-cells in the target of the phandle would allow this, but I
don't think this is something the pinctrl node should dictate to those
who reference it; it's quite legitimate for a GPIO node to use the pure
numeric mapping even if the pin controller happens to expose some pin
groups that allow you to do the mapping by name.

I actually had a version of the patch with #gpio-range-cells specifying
the format (one argument for named ranges, three for classical ranges)
before deciding to use a separate property and sending that version. As
I said in a previous mail, I don't have a preference which of the
following three possibilities to use and would be grateful for some
guidance (if it matters at all).

1.) separate property:
	gpio {
		gpio-ranges = <&pinctrl1 0 0 5>;
		gpio-range-groups = <&pinctrl2 5>;
		gpio-range-group-names = "gpios";
	};

Multiple properties seems a little like over-kill, although I agree it
makes specifying the format of the properties simplest.

2.) fixed number of three arguments:
	gpio {
		gpio-ranges = <&pinctrl1 0 0 5>, <&pinctrl2 5 0 0>;
		gpio-range-names = "", "gpios";
	};

This one seems fine to me. In many ways it's the simplest.

I guess I'd be OK with either (1) or (2) if someone else had a strong
opinion either way, although I'd tend towards (2) myself I think.

It's a pity properties don't carry type information in them, or we could
just put the string inline with the numbers in gpio-ranges:-(

3.) pinctrl-defined format.
	pinctrl1: pctl1 {
		#gpio-range-cells = <3>;
	};
	pinctrl2: pctl2 {
		#gpio-range-cells = <1>;
	};
	gpio {
		gpio-ranges = <&pinctrl1 0 0 5>, <&pinctrl2 5>;
		gpio-range-names = "", "gpios";
	};

I don't like that, because the pin controller node shouldn't determine
the format of the gpio-ranges entries here; a DT author would always
have the choice to use purely numerical values in gpio-ranges even if
the pinctrl node's binding did actually define named pin groups that
would allow you to use group names. Hence, the concept of the pinctrl
node having a #gpio-range-cells property seems wrong to me.