[PATCH 1/2] drivers: create a pinmux subsystem v3

[Linus Walleij]

On Sat, Jul 9, 2011 at 12:23 PM, Mark Brown
<broonie at opensource.wolfsonmicro.com> wrote:
> On Mon, Jun 13, 2011 at 01:57:36PM -0600, Grant Likely wrote:
>> On Mon, Jun 13, 2011 at 10:58 AM, Linus Walleij
>>
>> I would *strongly* recommend against individual device drivers
>> accessing the pinmux api.  This is system level configuration code,
>> and should be handled at the system level.
>
> There can also be advantages to putting the pin into the designed mode
> without the driver being loaded from the electrical point of view.  For
> example, selecting appropriate pull values for pads can cut down on
> power consumption.

Since the pin control subsystem is reference counting wrt
mux settings, one does not exclude the other. So for
example a driver may or may not grab a certain set-up of pins
and the core platform may do the same, but when they start to
request different conflicting things the subsystem will complain,
as is apropriate.

So this is a very pure driver framework, without policy, it just
does what it's told, and will prevent undefined and impossible
settings. Atleast that's the idea.

Thanks,
Linus Walleij