Re: [PATCH] power: bq27xxx_battery: Revert "Remove unneeded dependency in Kconfig"

[Andrew F. Davis]

On 11/09/2015 07:50 AM, Arnd Bergmann wrote:
> The dependency was clearly needed, without it it is possible to
> build the core i2c driver as a loadable module and the bq27xxx
> driver built-in, which results in link errors:
>
> drivers/built-in.o: In function `bq27xxx_battery_i2c_read':
> binder.c:(.text+0x360bf0): undefined reference to `i2c_transfer'
> binder.c:(.text+0x360c10): undefined reference to `i2c_transfer'
> drivers/built-in.o: In function `bq27xxx_battery_init':
> binder.c:(.init.text+0xe668): undefined reference to `i2c_register_driver'
> drivers/built-in.o: In function `bq27xxx_battery_exit':
> binder.c:(.exit.text+0x1a0c): undefined reference to `i2c_del_driver'
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Fixes: 6bd03ce3c12a ("power: bq27xxx_battery: Remove unneeded dependency in Kconfig")
> ---
> The bug was originally found and fixed by Xiong Zhou, but Andrew Davis
> broke it again by reverting the fix.
>
> I found it today on my ARM randconfig builds.
>
> diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
> index 237d7aa73e8c..9f53fb74ae6f 100644
> --- a/drivers/power/Kconfig
> +++ b/drivers/power/Kconfig
> @@ -159,6 +159,7 @@ config BATTERY_SBS
>
>   config BATTERY_BQ27XXX
>   	tristate "BQ27xxx battery driver"
> +	depends on I2C || I2C=n
>   	help
>   	  Say Y here to enable support for batteries with BQ27xxx (I2C/HDQ) chips.

Nothing enabled by BATTERY_BQ27XXX depends on I2C, this workaround is not
correct as it prevents BATTERY_BQ27XXX from being built-in when I2C is a
module, there is no reason for this limitation.

The undefined references are caused by BATTERY_BQ27XXX being built-in AND
its I2C functionality being enabled (BATTERY_BQ27XXX_I2C) while I2C is a
module. Reorganizing this driver is being discussed anyway, but in the
meantime a more correct fix would be along the lines of:

diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index 6de6ec2..d1d32f9 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -167,6 +167,7 @@ config BATTERY_BQ27XXX_I2C
        bool "BQ27xxx I2C support"
        depends on BATTERY_BQ27XXX
        depends on I2C
+       depends on !(I2C=m && BATTERY_BQ27XXX=y)
        default y
        help
          Say Y here to enable support for batteries with BQ27xxx (I2C) chips.
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