i2c: mux: fix up dependencies

We get the following build error from UM Linux after adding
an entry to drivers/iio/gyro/Kconfig that issues "select I2C_MUX":

ERROR: "devm_ioremap_resource"
   [drivers/i2c/muxes/i2c-mux-reg.ko] undefined!
ERROR: "of_address_to_resource"
   [drivers/i2c/muxes/i2c-mux-reg.ko] undefined!

It appears that the I2C mux core code actually only requires
CONFIG_OF, but depends on HAS_IOMEM for historical reasons,
while CONFIG_I2C_MUX_REG does *not* have a direct dependency
on HAS_IOMEM.

This creates a situation where a allyesconfig or allmodconfig
for UM Linux will select I2C_MUX, and will implicitly enable
I2C_MUX_REG as well, and the compilation will fail for the
register driver.

Fix this up by making I2C_MUX_REG depend on HAS_IOMEM and
the I2C_MUX depend on OF.

Cc: stable@vger.kernel.org
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Reported-by: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
Cc: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
Cc: Peter Rosin <peda@axentia.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/i2c/Kconfig       | 2 +-
 drivers/i2c/muxes/Kconfig | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

On 2016-11-14 14:03, Linus Walleij wrote:
> We get the following build error from UM Linux after adding
> an entry to drivers/iio/gyro/Kconfig that issues "select I2C_MUX":
> 
> ERROR: "devm_ioremap_resource"
>    [drivers/i2c/muxes/i2c-mux-reg.ko] undefined!
> ERROR: "of_address_to_resource"
>    [drivers/i2c/muxes/i2c-mux-reg.ko] undefined!
> 
> It appears that the I2C mux core code actually only requires
> CONFIG_OF, but depends on HAS_IOMEM for historical reasons,
> while CONFIG_I2C_MUX_REG does *not* have a direct dependency
> on HAS_IOMEM.
> 
> This creates a situation where a allyesconfig or allmodconfig
> for UM Linux will select I2C_MUX, and will implicitly enable
> I2C_MUX_REG as well, and the compilation will fail for the
> register driver.
> 
> Fix this up by making I2C_MUX_REG depend on HAS_IOMEM and
> the I2C_MUX depend on OF.
> 
> Cc: stable@vger.kernel.org
> Reported-by: kbuild test robot <fengguang.wu@intel.com>
> Reported-by: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
> Cc: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
> Cc: Peter Rosin <peda@axentia.se>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/i2c/Kconfig       | 2 +-
>  drivers/i2c/muxes/Kconfig | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
> index d223650a97e4..b9e378cfe1d1 100644
> --- a/drivers/i2c/Kconfig
> +++ b/drivers/i2c/Kconfig
> @@ -59,7 +59,7 @@ config I2C_CHARDEV
>  
>  config I2C_MUX
>  	tristate "I2C bus multiplexing support"
> -	depends on HAS_IOMEM
> +	depends on OF

It is not obvious to me that the i2c mux is dependent on
CONFIG_OF. Sure, there are unconditional calls to things like
of_property_read_u32 etc, but those are meant to be compiled
away for the !CONFIG_OF case. I think. The code predates me,
but that's how I read it...

So, I agree the HAS_IOMEM is probably hysterical remains from
some point when i2c-mux was perhaps a specific thing that actually
controlled the mux using IOMEM from code under that config option,
and it should probably be moved to where it is needed (below).

But don't add "depends on OF", or am I missing something?

Cheers,
Peter

>  	help
>  	  Say Y here if you want the I2C core to support the ability to
>  	  handle multiplexed I2C bus topologies, by presenting each
> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
> index e280c8ecc0b5..96de9ce5669b 100644
> --- a/drivers/i2c/muxes/Kconfig
> +++ b/drivers/i2c/muxes/Kconfig
> @@ -63,6 +63,7 @@ config I2C_MUX_PINCTRL
>  
>  config I2C_MUX_REG
>  	tristate "Register-based I2C multiplexer"
> +	depends on HAS_IOMEM
>  	help
>  	  If you say yes to this option, support will be included for a
>  	  register based I2C multiplexer. This driver provides access to
> 

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On Mon, Nov 14, 2016 at 2:59 PM, Peter Rosin <peda@axentia.se> wrote:

> It is not obvious to me that the i2c mux is dependent on
> CONFIG_OF. Sure, there are unconditional calls to things like
> of_property_read_u32 etc, but those are meant to be compiled
> away for the !CONFIG_OF case. I think. The code predates me,
> but that's how I read it...
(...)
> But don't add "depends on OF", or am I missing something?

Yeah that's right I guess. It can also use ACPI.

I'll update.

Yours,
Linus Walleij
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