On 06/14/2013 03:12 AM, Christian Ruppert wrote:

On Thu, Jun 13, 2013 at 03:38:09PM -0600, Stephen Warren wrote:

quoted

On 06/13/2013 06:55 AM, Christian Ruppert wrote:

quoted

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

That's not exactly true. The existing gpio-ranges property already
allows non-linear ranges to be represented quite easily; each entry in
the gpio-ranges list is <gpio-base> <pinctrl-base> <count>, so you can
piece together any mapping you want.

You're right, my description is somewhat imprecise here.

quoted

The potential advantage of this patch is that the pinctrl-side of the
mapping can be a group name rather than pin IDs, which might reduce the
size of the mapping list if you have an extremely sparse or non-linear
mapping /and/ parts of that mapping just happen to align with the pin
groups in the pin controller HW, since each entry in the gpio-ranges
property can be sparse/non-linear, rather than being a small linear
chunk of the mapping.

Pin controller authors have the freedom to define pin groups just for
the purpose of "predefining" the pinctrl side of GPIO ranges.

Hmm. I suppose that's true. I'm not sure how enthusiastic I am about
doing this though... The reason I'm unsure is because it starts using
pin groups from something other than groups of pins in HW that are all
affected by the same mux or config bits in a register, and starts using
pin groups for something else; GPIO<->pinmux pins mapping. Perhaps it's
OK though, considering the other abuses of pin groups that are already
present, such as using pin groups to represent default/common uses of
groups of pins that don't actually exist in HW.