linux-kernel - Re: drivers/input/touchscreen/cyttsp_i2c.c:47:18: error: implicit declaration of function 'i2c

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Message-ID: <CACRpkdZmKfNWF7ciHJMi4JU+_JnxjWD_kMhfxFOeydQ11Vyc4Q@mail.gmail.com>
Date: Wed, 2 Oct 2024 15:37:56 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>, Arnd Bergmann <arnd@...db.de>
Cc: kernel test robot <lkp@...el.com>, oe-kbuild-all@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Javier Martinez Canillas <javierm@...hat.com>
Subject: Re: drivers/input/touchscreen/cyttsp_i2c.c:47:18: error: implicit
 declaration of function 'i2c_transfer'

On Wed, Oct 2, 2024 at 11:31 AM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:

> >    drivers/input/touchscreen/cyttsp_i2c.c:118:26: warning: 'cyttsp_i2c_driver' defined but not used [-Wunused-variable]
> >      118 | static struct i2c_driver cyttsp_i2c_driver = {
> >          |                          ^~~~~~~~~~~~~~~~~
> >    cc1: some warnings being treated as errors
> >
>
> This is really weird: cyttsp_i2c.h includes linux/i2c.h, it has
> dependency in Kconfig on I2C and CONFIG_I2C is present in the .config
> referenced above, so all the declarations should be there.

I usually ask Arnd about all kind of Kconfig business when
things get weird.

But could it be one of these awful things:

config TOUCHSCREEN_CYTTSP_I2C
        tristate "support I2C bus connection"
-        depends on TOUCHSCREEN_CYTTSP_CORE && I2C
+       depends on TOUCHSCREEN_CYTTSP_CORE && (I2C=y ||
I2C=TOUCHSCREEN_CYTTSP_CORE)

Since I2C is tristate it could be a module and then this touchscreen
has to be a module too.

Yours,
Linus Walleij