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power_supply: Make the core a boolean instead of a tristate

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On Mon, Apr 02, 2012 at 01:53:23PM +1000, Benjamin Herrenschmidt wrote:
> > drivers/built-in.o: In function `.nouveau_pm_trigger':
> > (.text+0xa56e8): undefined reference to `.power_supply_is_system_supplied'
> >
> > nouveau probably needs to depends on CONFIG_POWER_SUPPLY to force a module
> > build with the latter is =m
>
> Ok, not that trivial...
>
> The problem is more like POWER_SUPPLY should be a bool, not a tristate.
>
> If you think about it: you don't want things like nouveau to depend on a
> random subsystem like that, people will never get it. In fact,
> POWER_SUPPLY provides empty inline stubs when not enabled, so that's
> really designed to not have depends...
>
> However that -cannot- work if POWER_SUPPLY is modular and the drivers
> who use it are not.
>
> The only fixes here that make sense I can think of
> that don't also involve Kconfig horrors are:
>
>  - Ugly: in power_supply.h, use the extern variant if
>
>       defined(CONFIG_POWER_SUPPLY) ||
>        (defined(CONFIG_POWER_SUPPLY_MODULE) && defined(MODULE))
>
> IE. use the stub if power supply is a module and what is being built is
> built-in. Of course that's not only ugly, it somewhat sucks from a user
> perspective as the subsystem now exists but can't be used by some
> drivers...
>
>  - Better: Just make the bloody thing a bool :-) The power supply
> framework itself is small enough, just make it a boolean option and
> avoid the problem entirely. The actual power supply sub drivers can
> remain modular of course.

Suggested-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
This commit is contained in:
Anton Vorontsov 2012-05-04 21:06:19 -07:00 committed by Anton Vorontsov
parent a2ebfe2fc6
commit 0d4ed4e27a
2 changed files with 2 additions and 2 deletions
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2
drivers/power/Kconfig
View File

@ -1,5 +1,5 @@
menuconfig POWER_SUPPLY
tristate "Power supply class support"
bool "Power supply class support"
help
Say Y here to enable power supply class support. This allows
power supply (batteries, AC, USB) monitoring by userspace

2
include/linux/power_supply.h
View File

@ -212,7 +212,7 @@ extern void power_supply_changed(struct power_supply *psy);
extern int power_supply_am_i_supplied(struct power_supply *psy);
extern int power_supply_set_battery_charged(struct power_supply *psy);
#if defined(CONFIG_POWER_SUPPLY) || defined(CONFIG_POWER_SUPPLY_MODULE)
#ifdef CONFIG_POWER_SUPPLY
extern int power_supply_is_system_supplied(void);
#else
static inline int power_supply_is_system_supplied(void) { return -ENOSYS; }