Re: [PATCH v2] iio: accel: add Freescale MMA7455L/MMA7456L 3-axis accelerometer driver

[Lars-Peter Clausen <lars@metafoo.de>]

On 10/19/2015 09:00 PM, Joachim Eastwood wrote:
[...]
> +config MMA7455
> +	tristate "Freescale MMA7455L/MMA7456L Accelerometer Driver"
> +	depends on I2C || SPI_MASTER
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	select MMA7455_I2C if I2C
> +	select MMA7455_SPI if SPI

Ah, damm, I shouldn't have said bmg160 is a good example without actually
looking at its Kconfig entry. Only saw the C files and those looked good.

This is still problematic. The depends on clause allows this driver to be
built-in if either I2C is built-in or SPI_MASTER is built-in. And then the
respective I2C and SPI modules will also be selected as built-in even though
the I2C symbol is only selected as a module. So you now have built-in code
that tries to reference code that is only available as a module.

A better solution is to make the Kconfig entries for the I2C and SPI modules
user selectable and then let them select the main module.

> +	help
> +	  Say yes here to build support for the Freescale MMA7455L and
> +	  MMA7456L 3-axis accelerometer.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called mma7455_i2c or mma7455_spi.
> +
> +config MMA7455_I2C
> +	tristate
> +	select REGMAP_I2C
> +
> +config MMA7455_SPI
> +	tristate
> +	select REGMAP_SPI
> +