linux-kernel - Re: [PATCH] gpio: winbond: fix ISA_BUS

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Date:   Thu, 11 Jan 2018 10:18:56 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: winbond: fix ISA_BUS_API dependency

On Thu, Jan 11, 2018 at 9:35 AM, Arnd Bergmann <arnd@...db.de> wrote:

> The newly added GPIO driver for winbond chipsets causes a
> circular dependency warning in Kconfig:
>
> drivers/gpio/Kconfig:13:error: recursive dependency detected!
> drivers/gpio/Kconfig:13:        symbol GPIOLIB is selected by STX104
> drivers/iio/adc/Kconfig:699:    symbol STX104 depends on ISA_BUS_API
> arch/Kconfig:830:       symbol ISA_BUS_API is selected by GPIO_WINBOND
> drivers/gpio/Kconfig:701:       symbol GPIO_WINBOND depends on GPIOLIB
>
> The underlying problem is that ISA_BUS_API is not meant to be selected by
> device drivers, instead it is provided by the architectures that support
> ISA add-on card devices, or in case of x86 have this explicitly enabled.
>
> This particular driver appears to be different from the other ISA_BUS_API
> based drivers, in that it is not normally an add-on card (ISA or PC104)
> but instead is an LPC-attached component on the mainboard. We already
> support other functionality provided by this chip, at least
> drivers/watchdog/w83627hf_wdt.c and drivers/hwmon/w83627ehf.c, plus
> there is a discovery function for this hardware in
> drivers/parport/parport_pc.c.
>
> If we want to use this driver without having to enable CONFIG_EXPERT,
> it might be better to not use the isa_bus_type for it, but rather
> turn it into a platform_driver, acpi_driver or add an MFD for it that
> is shared with the wdt and hwmon portions and does the probing.
>
> For now, this patch fixes the dependency by changing 'select' into
> 'depends on'.
>
> Cc: William Breathitt Gray <vilhelm.gray@...il.com>
> Cc: Guenter Roeck <linux@...ck-us.net>
> Cc: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Fixes: a0d65009411c ("gpio: winbond: Add driver")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

I've tentatively applied this patch so we don't break the builds.

We had a bunch of discussion about this already ... I guess we
need to go at it again, waiting for comments from Maciej and
William.

Yours,
Linus Walleij