rework pm_ops pm_disk_mode, kill misuse

This patch series cleans up some misconceptions about pm_ops.  Some users of
the pm_ops structure attempt to use it to stop the user from entering suspend
to disk, this, however, is not possible since the user can always use
"shutdown" in /sys/power/disk and then the pm_ops are never invoked.  Also,
platforms that don't support suspend to disk simply should not allow
configuring SOFTWARE_SUSPEND (read the help text on it, it only selects
suspend to disk and nothing else, all the other stuff depends on PM).

The pm_ops structure is actually intended to provide a way to enter
platform-defined sleep states (currently supported states are "standby" and
"mem" (suspend to ram)) and additionally (if SOFTWARE_SUSPEND is configured)
allows a platform to support a platform specific way to enter low-power mode
once everything has been saved to disk.  This is currently only used by ACPI
(S4).

This patch:

The pm_ops.pm_disk_mode is used in totally bogus ways since nobody really
seems to understand what it actually does.

This patch clarifies the pm_disk_mode description.

It also removes all the arm and sh users that think they can veto suspend to
disk via pm_ops; not so since the user can always do echo shutdown >
/sys/power/disk, they need to find a better way involving Kconfig or such.

ACPI is the only user left with a non-zero pm_disk_mode.

The patch also sets the default mode to shutdown again, but when a new pm_ops
is registered its pm_disk_mode is selected as default, that way the default
stays for ACPI where it is apparently required.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: <linux-pm@lists.linux-foundation.org>
Cc: Len Brown <lenb@kernel.org>
Acked-by: Russell King <rmk@arm.linux.org.uk>
Cc: Greg KH <greg@kroah.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 11 deletions

diff --git a/include/linux/pm.h b/include/linux/pm.h
index 9bd86db4d39..dfced9188bd 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -112,6 +112,8 @@ typedef int __bitwise suspend_state_t;
 
 typedef int __bitwise suspend_disk_method_t;
 
+/* invalid must be 0 so struct pm_ops initialisers can leave it out */
+#define PM_DISK_INVALID		((__force suspend_disk_method_t) 0)
 #define	PM_DISK_FIRMWARE	((__force suspend_disk_method_t) 1)
 #define	PM_DISK_PLATFORM	((__force suspend_disk_method_t) 2)
 #define	PM_DISK_SHUTDOWN	((__force suspend_disk_method_t) 3)
@@ -137,17 +139,16 @@ typedef int __bitwise suspend_disk_method_t;
  * @finish: Called when the system has left the given state and all devices
  *	are resumed. The return value is ignored.
  *
- * @pm_disk_mode: Set to the disk method that the user should be able to
- *	configure for suspend-to-disk. Since %PM_DISK_SHUTDOWN,
- *	%PM_DISK_REBOOT, %PM_DISK_TEST and %PM_DISK_TESTPROC
- *	are always allowed, currently only %PM_DISK_PLATFORM
- *	makes sense. If the user then choses %PM_DISK_PLATFORM,
- *	the @prepare call will be called before suspending to disk
- *	(if present), the @enter call should be present and will
- *	be called after all state has been saved and the machine
- *	is ready to be shut down/suspended/..., and the @finish
- *	callback is called after state has been restored. All
- *	these calls are called with %PM_SUSPEND_DISK as the state.
+ * @pm_disk_mode: The generic code always allows one of the shutdown methods
+ *	%PM_DISK_SHUTDOWN, %PM_DISK_REBOOT, %PM_DISK_TEST and
+ *	%PM_DISK_TESTPROC. If this variable is set, the mode it is set
+ *	to is allowed in addition to those modes and is also made default.
+ *	When this mode is sent selected, the @prepare call will be called
+ *	before suspending to disk (if present), the @enter call should be
+ *	present and will be called after all state has been saved and the
+ *	machine is ready to be powered off; the @finish callback is called
+ *	after state has been restored. All these calls are called with
+ *	%PM_SUSPEND_DISK as the state.
  */
 struct pm_ops {
 	int (*valid)(suspend_state_t state);