On Thu, Dec 6, 2012 at 8:45 AM, Alexandre Courbot [off-list ref] wrote:

With the current API, GPIOs are manipulated through an integer which
represents their unique number across the system. This poses problems in
terms of portability, scalability and flexibility: for instance, the
number of valid GPIOs for a given system is fixed at system time, and a
large array of that size is statically allocated to hold the GPIO
descriptors. Worse, GPIOs can be used without being properly allocated.

In order to improve the situation, the integer namespace must first get
away. This patch introduces an alternative GPIO API that uses opaque
handlers and refactor gpiolib's internals to work with these handlers
instead of GPIO numbers. The former integer-based API is still available
as a light wrapper around this new API.

This first step will then us to build more improvements for gpiolib,
like proper GPIO lookup functions per device and provider, and getting
rid of the static GPIO array and the ARCH_NR_GPIO configuration option.

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

I really like this. It is looking very good.

Especially it's nice that it makes GPIO descriptors the norm
rather than a bolt-on, and the old linear GPIO space is turned
into a comaptibility layer using static inlines.

I'd like to see some love for Documentation/gpio.txt to reflect
the changes, plus considering Grants note, and I will be happy
to add Reviewed-by on this.

Especially the lookups will be nice to see going forward!

Yours,
Linus Walleij