power management: change /sys/power/disk display

Change /sys/power/disk to display all valid modes as well as the currently
selected one in a fashion known from the LED subsystem.

This changes userspace API, but it is apparently not used much (we asked
some userspace developers)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: "Rafael J. Wysocki" <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
index 8c5b41b..fd5192a 100644
--- a/Documentation/power/interface.txt
+++ b/Documentation/power/interface.txt
@@ -34,8 +34,12 @@
 we are able to look in the log messages and work out, for example, which code
 is being slow and which device drivers are misbehaving.
 
-Reading from this file will display what the mode is currently set
-to. Writing to this file will accept one of
+Reading from this file will display all supported modes and the currently
+selected one in brackets, for example
+
+	[shutdown] reboot test testproc
+
+Writing to this file will accept one of
 
        'platform' (only if the platform supports it)
        'shutdown'
diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index e518379..0633137 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -350,7 +350,34 @@
 
 static ssize_t disk_show(struct kset *kset, char *buf)
 {
-	return sprintf(buf, "%s\n", pm_disk_modes[pm_disk_mode]);
+	int i;
+	char *start = buf;
+
+	for (i = PM_DISK_PLATFORM; i < PM_DISK_MAX; i++) {
+		if (!pm_disk_modes[i])
+			continue;
+		switch (i) {
+		case PM_DISK_SHUTDOWN:
+		case PM_DISK_REBOOT:
+		case PM_DISK_TEST:
+		case PM_DISK_TESTPROC:
+			break;
+		default:
+			if (pm_ops && pm_ops->enter &&
+			    (i == pm_ops->pm_disk_mode))
+				break;
+			/* not a valid mode, continue with loop */
+			continue;
+		}
+		if (i == pm_disk_mode)
+			buf += sprintf(buf, "[%s]", pm_disk_modes[i]);
+		else
+			buf += sprintf(buf, "%s", pm_disk_modes[i]);
+		if (i+1 != PM_DISK_MAX)
+			buf += sprintf(buf, " ");
+	}
+	buf += sprintf(buf, "\n");
+	return buf-start;
 }