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Date: Wed, 9 Feb 2011 01:37:52 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Ingo Molnar <mingo@...e.hu>,
Mark Brown <broonie@...nsource.wolfsonmicro.com>,
Len Brown <len.brown@...el.com>,
Alan Stern <stern@...land.harvard.edu>,
linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
linux-embedded@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/5] ACPI / PM: Move references to pm_flags into sleep.c
On Wednesday, February 09, 2011, Linus Torvalds wrote:
> On Tue, Feb 8, 2011 at 1:20 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> >
> > If direct references to pm_flags are moved from bus.c to sleep.c,
> > CONFIG_ACPI will not need to depend on CONFIG_PM any more.
>
> The patch may _work_, but I really hate it. That function naming is insane:
>
> > #ifdef CONFIG_ACPI_SLEEP
> > #else
> > +static inline bool acpi_pm_enabled(void) { return true; }
>
> acpi_pm_enabled() returns true if ACPI_SLEEP is _not_ enabled? That's
> just crazy.
>
> ... followed by more crazy:
>
> > +bool acpi_pm_enabled(void)
> > +{
> > + if (!(pm_flags & PM_APM)) {
> > + pm_flags |= PM_ACPI;
> > + return true;
> > + }
> > + return false;
> > +}
>
> IOW, that function doesn't do anything _remotely_ like what the naming
> indicates.
>
> Any sane person would expect that a function called
> 'acpi_pm_enabled()' would return true if ACPI PM was enabled, and
> false otherwise. But it's not what it does at all. Instead, what it
> does is to say "if APM isn't enabled, let's enable ACPI and return
> true". Except then for the non-ACPI sleep case, we just return true
> regardless, which still looks damn odd, wouldn't you say?
>
> That isn't good. Maybe it all does what you want it to do, but from a
> code readability standpoint, it's just one honking big "WTF?". Please
> don't do that. Call it something else. Make the naming actually follow
> what the semantics are. Appropriate naming should also make it
> sensible to return "true" when ACPI_SLEEP is disabled, and should make
> the caller look sane.
>
> Now, I don't know what that particular naming might be,
I had the same problem and I must admit I'm not good at inventing function
names.
> but maybe it would be about APM being enabled. Which is what the caller
> actually seems to care about and talks about for the failure case. Maybe
> you need separate functions for the "is APM enabled" case for the naming
> to make sense. Hmm?
That sounds like a good idea. What about the following patch?
---
From: Rafael J. Wysocki <rjw@...k.pl>
Subject: PM / ACPI: Remove references to pm_flags from bus.c
If direct references to pm_flags are removed from drivers/acpi/bus.c,
CONFIG_ACPI will not need to depend on CONFIG_PM any more. Make that
happen.
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
drivers/acpi/Kconfig | 1 -
drivers/acpi/bus.c | 7 ++++---
include/linux/suspend.h | 6 ++++++
kernel/power/main.c | 12 +++++++++++-
4 files changed, 21 insertions(+), 5 deletions(-)
Index: linux-2.6/drivers/acpi/bus.c
===================================================================
--- linux-2.6.orig/drivers/acpi/bus.c
+++ linux-2.6/drivers/acpi/bus.c
@@ -40,6 +40,7 @@
#include <acpi/acpi_bus.h>
#include <acpi/acpi_drivers.h>
#include <linux/dmi.h>
+#include <linux/suspend.h>
#include "internal.h"
@@ -1025,13 +1026,13 @@ static int __init acpi_init(void)
if (!result) {
pci_mmcfg_late_init();
- if (!(pm_flags & PM_APM))
- pm_flags |= PM_ACPI;
- else {
+ if (pm_apm_enabled()) {
printk(KERN_INFO PREFIX
"APM is already active, exiting\n");
disable_acpi();
result = -ENODEV;
+ } else {
+ pm_set_acpi_flag();
}
} else
disable_acpi();
Index: linux-2.6/drivers/acpi/Kconfig
===================================================================
--- linux-2.6.orig/drivers/acpi/Kconfig
+++ linux-2.6/drivers/acpi/Kconfig
@@ -7,7 +7,6 @@ menuconfig ACPI
depends on !IA64_HP_SIM
depends on IA64 || X86
depends on PCI
- depends on PM
select PNP
default y
help
Index: linux-2.6/include/linux/suspend.h
===================================================================
--- linux-2.6.orig/include/linux/suspend.h
+++ linux-2.6/include/linux/suspend.h
@@ -272,6 +272,9 @@ extern int unregister_pm_notifier(struct
register_pm_notifier(&fn##_nb); \
}
+extern bool pm_apm_enabled(void);
+extern void pm_set_acpi_flag(void);
+
/* drivers/base/power/wakeup.c */
extern bool events_check_enabled;
@@ -292,6 +295,9 @@ static inline int unregister_pm_notifier
#define pm_notifier(fn, pri) do { (void)(fn); } while (0)
+static inline bool pm_apm_enabled(void) { return false; }
+static inline void pm_set_acpi_flag(void) {}
+
static inline bool pm_wakeup_pending(void) { return false; }
#endif /* !CONFIG_PM_SLEEP */
Index: linux-2.6/kernel/power/main.c
===================================================================
--- linux-2.6.orig/kernel/power/main.c
+++ linux-2.6/kernel/power/main.c
@@ -17,10 +17,20 @@
DEFINE_MUTEX(pm_mutex);
+#ifdef CONFIG_PM_SLEEP
+
unsigned int pm_flags;
EXPORT_SYMBOL(pm_flags);
-#ifdef CONFIG_PM_SLEEP
+bool pm_apm_enabled(void)
+{
+ return !!(pm_flags & PM_APM);
+}
+
+void pm_set_acpi_flag(void)
+{
+ pm_flags |= PM_ACPI;
+}
/* Routines for PM-transition notifications */
--
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