linux-kernel - Re: [tip:x86/platform 1/1] platform_bt.c:undefined reference to `gpiod_add_lookup

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Date:   Fri, 7 Apr 2017 12:36:47 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        kbuild test robot <fengguang.wu@...el.com>,
        "kbuild-all@...org" <kbuild-all@...org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        tipbuild@...or.com, Ingo Molnar <mingo@...nel.org>
Subject: Re: [tip:x86/platform 1/1] platform_bt.c:undefined reference to `gpiod_add_lookup_table'

On Fri, Apr 7, 2017 at 10:57 AM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Fri, Apr 7, 2017 at 11:16 AM, Linus Walleij <linus.walleij@...aro.org> wrote:

>> If it is just a stub without much code I guess that is prettier, but
>> still it is a bit weird, because I guess the table that are passed
>> to gpiod_add_lookup_table() will still be compiled into the object
>> so you are anyways carrying cruft, and then what is the point in
>> not just doing select GPIOLIB.
>
> Because it's optional to HCIUART_BCM as far as I know. But I didn't
> look closer to possibilities there (IIRC there no *_optional() calls
> to GPIOLIB).

Do you mean for adding tables?
We have:
devm_gpiod_get_optional() & friends.

They return NULL if the GPIO is not there, or if the
GPIO library is compiled out (as of HEAD, due to the
patch from Dmitry T.)

>> IMO SFI is just another hardware description language, and
>> SFI-described GPIO should be in drivers/gpio/gpiolib-sfi.c or
>> something like this akin to ACPI and OF. Why is it contained as
>> platform hacks?
>
> We have already discussed this a lot when I proposed to create
> something like gpiolib-sfi.c. We have only legacy stuff with SFI amd
> SFI perse is 99% useless. To not uglify drivers we in any case have to
> hardcode mappings between weird SFI names to what drivers are
> expecting.
> So, it does not worth doing it.

Aha OK. Yeah you know this way better than me so I trust
you on this.


>> So I'm a bit worried that we are seeing a symptom of board data
>> stockpiling in arch/x86 and not really a GPIO compilation problem.
>
> Don't be. I'm trying to avoid this and my plan is actually to modify
> bootloader on that board to provide ACPI tables instead. This will
> hide all crappy stuff in bootloader, though we better to support
> legacy (stock) bootloader as well and thus platform data.

OK sounds reasonable. Kind of like the attached device tree we
do on ARM.

Yours,
Linus Walleij