Re: [PATCH 3/3] power: bq27xxx_battery: fix defined but not used warnings

[Andrew F. Davis]

On 10/19/2015 04:37 AM, Sebastian Reichel wrote:
> On Fri, Oct 16, 2015 at 10:01:33AM -0500, Andrew F. Davis wrote:
> > On 10/16/2015 09:47 AM, Pali Rohár wrote:
> > > On Friday 16 October 2015 15:44:12 Sebastian Reichel wrote:
> > > > If BQ27XXX is enabled, but neither I2C based initialization, nor
> > > > platform based initialization are activated, bq27xxx_powersupply_init
> > > > and bq27xxx_powersupply_unregister are defined but not used.
> > > >
> > > > This configuration doesn't make sense, but there is no easy way
> > > > to make it unavailable in the build system, so just mark the
> > > > functions as __maybe_unused instead.
> > >
> > > What about?
> > >
> > > #if defined(CONFIG_1) || defined(CONFIG_2)
> > > #define NEED_POWER_SUPPLY
> > > #endif
> > >
> > > And then wrap power supply code into #ifdef NEED_POWER_SUPPLY?
>
> I thought about wrapping the whole code in an ifdef, but I don't
> think compiling an empty file is any better than adding the
> __maybe_unused flag.
>
> > We would need to wrap everything in that then, so without I2C or
> > platform enabled we end up compiling an empty file. I think the
> > better fix would be to modify the Kconfig, something like:
>
> Handling this in Kconfig is preferred of course.
>
> > config BATTERY_BQ27XXX
> > 	tristate
> > 	depends on (BATTERY_BQ27XXX_I2C || BATTERY_BQ27XXX_PLATFORM)
> > 	default y
> >
> > config BATTERY_BQ27XXX_I2C
> > 	bool "BQ27200/BQ27500 support"
> > 	depends on I2C
> > 	help
> > 	  Say Y here to enable support for batteries with BQ27x00 (I2C) chips.
> >
> > config BATTERY_BQ27XXX_PLATFORM
> > 	bool "BQ27000 support"
> > 	help
> > 	  Say Y here to enable support for batteries with BQ27000 (HDQ) chips.
> >
> > This would be more in line with how other multi-bus devices handle
> > this issue when nether bus is selected.
>
> If I'm not mistaken, this way it's impossible to build the code as
> module. You need to move the tristate to the individual bus options.
> This would require to split the code, so that two separate modules
> are built. I checked the tree and found a few examples:
>
>   * building one modules for each bus, core support is autoselected, but always built-in
>    - BMP085
>
>   * building a core modules + one module for each bus
>    - AD525X_DPOT
>    - ADE7854
>    - ADT7316
>    - INPUT_AD714X
>    - INPUT_ADXL34X
>    - TOUCHSCREEN_AD7879
>    - TOUCHSCREEN_CYTTSP_CORE
>    - TOUCHSCREEN_CYTTSP4_CORE
>
> Instead of restructuring the whole driver, we could also just built
> the platform code unconditionally. The platform specific code is
> just a probe + remove function and bq27xxx_battery_platform_read().
> The last one could be dropped, if the pdata->read function is
> modified (effectively moving the code into the w1 driver).
>
> -- Sebastian

A quick test shows the following Kconfig to work as desired, selecting one
or both buses as modules builds the driver as a module, if ether are
selected as built-in the whole driver is built-in.

config BATTERY_BQ27XXX
	tristate
	depends on (BATTERY_BQ27XXX_I2C || BATTERY_BQ27XXX_PLATFORM)
	default y

config BATTERY_BQ27XXX_I2C
	tristate "BQ27xxx I2C support"
	depends on I2C
	help
	  Say Y here to enable support for batteries with BQ27xxx (I2C) chips.

config BATTERY_BQ27XXX_PLATFORM
	tristate "BQ27xxx HDQ support"
	help
	  Say Y here to enable support for batteries with BQ27xxx (HDQ) chips.

We would then have to change:
#ifdef CONFIG_BATTERY_BQ27XXX_I2C

to

#if defined(CONFIG_BATTERY_BQ27XXX_I2C) || defined(CONFIG_BATTERY_BQ27XXX_I2C_MODULE)

(same for CONFIG_BATTERY_BQ27XXX_PLATFORM)

--
Andrew F. Davis
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