From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: [PATCH v2] Input: silead - Do not try to directly access the
 GPIO when using ACPI pm
Date: Thu, 09 Mar 2017 17:03:30 +0200
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To: Hans de Goede <hdegoede@redhat.com>, Mika Westerberg <mika.westerberg@linux.intel.com>, Daniel Vetter <daniel@ffwll.ch>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>, "russianneuromancer @ ya . ru" <russianneuromancer@ya.ru>, Gregor Riepl <onitake@gmail.com>, linux-input@vger.kernel.org, Linus Walleij <linus.walleij@linaro.org>

On Thu, 2017-03-09 at 15:45 +0100, Hans de Goede wrote:

> > Sounds like a plan!
> > 
> > Since extcon patches are landed already mainstream it might make
> > sense
> > to send it as usual to all maintainers.
> 
> Ack, so to be clear we should use gpiod_get not gpiod_get_index with
> the acpi mapping table, right ? The reason I'm asking is that my
> test devices only have the id pin which has index 0 so in my
> experience with soc_button_array it will work with both
> (the button with index 0 would even work with gpiod_get_index).

TL;DR -- right.


So, now simple and clean example:

_CRS:

GpioIo(...)  { pin #5 }
GpioIo(...)  { pin #3, pin #4, pin #2 }
GpioIo(...)  { pin #15 }

If we assume each line represents one function (connection ID):
"func0"
"func1"
"func2"

we would see that index is needed only when we would like to get access
to pin #4 or pin #2 of "func1".

Was:

gpiod_get_index(..., NULL, <index_in_CRS>);

where index is 0,1, or 2 *with second index assumed 0*!

Now, what we actually is doing we mapping connection ID to the first
index and can use index to access mentioned above pins:

gpiod_get_index(..., "<funcX>", <secondary_index_in_CRS>);

For example, for pin #2 or #4
gpiod_get_index(..., "func1", 2); // pin #2
gpiod_get_index(..., "func1", 1); // pin #4

Thus,
gpiod_get_index(..., "func1", 0); // pin #3


Or just for the first (virtual) column:

gpiod_get(..., "<funcX>");

where pin #5, #3 or #15 is accessible.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy