lkml.org 
[lkml]   [2012]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: How about a gpio_get(device *, char *) function?
Date
On Wed, 7 Nov 2012 22:28:01 +0100, Linus Walleij <linus.walleij@linaro.org> wrote:
> On Mon, Nov 5, 2012 at 6:35 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
> > [Me]
> >> gpio_get() should get an abstract handle just like clk_get() or
> >> regulator_get(), not a fixed numeral.
> >
> > I don't really see why the return type of gpio_get() influences whether
> > it can be implemented or not.
>
> It doesn't influence that, but I want to follow the opaqueness design
> pattern from irq descriptors and struct clk.

Right. I like the pattern too. Unforutunately that means dealing with
somewhere on the order of 2500 callers of the old API. :-(

However, I don't think that the GPIO numberspace issue is completely
intertwined with opaqifying the gpio handles. The numberspace can be
fixed with the current API if someone creates a sparse gpio
registrations.

I don't have any problem with a gpio_get function, but I do agree that
making it return an opaque handle is how it should be written with a new
set of accessors. The handle should probably be simply the pointer to
the &gpio_desc[number] which is a private table in gpiolib.c. The
definition of it isn't available outside of gpiolib.c

In fact, the old functions should be redefined in terms of getting the
gpio_desc from the irq number and calling the new functions.

>
> > With board files, some "gpio map" table would simply contain the same
> > int GPIO ID value the table as is used anywhere else already. With DT,
> > the same xlate function would translate from DT GPIO-chip-relative
> > IDs/specifiers into the global number space in the same way that we do
> > today via other APIs.
>
> Yes, this part I buy into, just want to see how we can move forward
> from there. The coplete nightmare is to introduce something into DT
> that nails down a global GPIO numberspace... but I think that is not
> the case atleast.
>
> > If the GPIO subsystem were reworked as you propose, this API could be
> > reworked in exactly the same way, or if implemented after the rework, it
> > would return whatever handle type was in use at the time.
>
> Yes, I just think we should return an opaque struct from day 1, so
> just a little, little bit more to shield us.
>
> Yours,
> Linus Walleij

--
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.


\
 
 \ /
  Last update: 2012-11-26 18:01    [W:0.266 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site