Message-Id: <201105211412.11782.rjw@sisk.pl>
Date:	Sat, 21 May 2011 14:12:11 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>
Cc:	Frank Hofmann <frank.hofmann@...tom.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-sh@...r.kernel.org,
	Ralf Baechle <ralf@...ux-mips.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: [PATCH 3/3] PM / Hibernate: Update kerneldoc comments in hibernate.c

From: Rafael J. Wysocki <rjw@...k.pl>

Some of the kerneldoc comments in kernel/power/hibernate.c are
outdated and some of them don't adhere to the kernel's standards.
Update them and make them look in a consistent way.

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
 kernel/power/hibernate.c |  184 ++++++++++++++++++++++++-----------------------
 1 file changed, 94 insertions(+), 90 deletions(-)

Index: linux-2.6/kernel/power/hibernate.c
===================================================================
--- linux-2.6.orig/kernel/power/hibernate.c
+++ linux-2.6/kernel/power/hibernate.c
@@ -55,10 +55,9 @@ static int hibernation_mode = HIBERNATIO
 static const struct platform_hibernation_ops *hibernation_ops;
 
 /**
- * hibernation_set_ops - set the global hibernate operations
- * @ops: the hibernation operations to use in subsequent hibernation transitions
+ * hibernation_set_ops - Set the global hibernate operations.
+ * @ops: Hibernation operations to use in subsequent hibernation transitions.
  */
-
 void hibernation_set_ops(const struct platform_hibernation_ops *ops)
 {
 	if (ops && !(ops->begin && ops->end &&  ops->pre_snapshot
@@ -115,10 +114,8 @@ static int hibernation_test(int level) {
 #endif /* !CONFIG_PM_DEBUG */
 
 /**
- *	platform_begin - tell the platform driver that we're starting
- *	hibernation
+ * platform_begin - Use platform driver to start hibernation.
  */
-
 static int platform_begin(int platform_mode)
 {
 	return (platform_mode && hibernation_ops) ?
@@ -126,10 +123,8 @@ static int platform_begin(int platform_m
 }
 
 /**
- *	platform_end - tell the platform driver that we've entered the
- *	working state
+ * platform_end - Use platform driver to finish transition to the working state.
  */
-
 static void platform_end(int platform_mode)
 {
 	if (platform_mode && hibernation_ops)
@@ -137,8 +132,10 @@ static void platform_end(int platform_mo
 }
 
 /**
- *	platform_pre_snapshot - prepare the machine for hibernation using the
- *	platform driver if so configured and return an error code if it fails
+ * platform_pre_snapshot - Call platform to prepare the machine for hibernation.
+ *
+ * Use the platform driver to prepare the system for creating a hibernate image,
+ * if so configured, and return an error code if that fails.
  */
 
 static int platform_pre_snapshot(int platform_mode)
@@ -148,10 +145,13 @@ static int platform_pre_snapshot(int pla
 }
 
 /**
- *	platform_leave - prepare the machine for switching to the normal mode
- *	of operation using the platform driver (called with interrupts disabled)
+ * platform_leave - Use platform to prepare a transition to the working state.
+ *
+ * Use the platform driver prepare to prepare the machine for switching to the
+ * normal mode of operation.
+ *
+ * This routine is called on one CPU with interrupts disabled.
  */
-
 static void platform_leave(int platform_mode)
 {
 	if (platform_mode && hibernation_ops)
@@ -159,10 +159,13 @@ static void platform_leave(int platform_
 }
 
 /**
- *	platform_finish - switch the machine to the normal mode of operation
- *	using the platform driver (must be called after platform_prepare())
+ * platform_finish - Use platform to switch the system to the working state.
+ *
+ * Use the platform driver to switch the machine to the normal mode of
+ * operation.
+ *
+ * This routine must be called after platform_prepare().
  */
-
 static void platform_finish(int platform_mode)
 {
 	if (platform_mode && hibernation_ops)
@@ -170,11 +173,14 @@ static void platform_finish(int platform
 }
 
 /**
- *	platform_pre_restore - prepare the platform for the restoration from a
- *	hibernation image.  If the restore fails after this function has been
- *	called, platform_restore_cleanup() must be called.
+ * platform_pre_restore - Prepare for hibernate image restoration.
+ *
+ * Use the platform driver to prepare the system for resume from a hibernation
+ * image.
+ *
+ * If the restore fails after this function has been called,
+ * platform_restore_cleanup() must be called.
  */
-
 static int platform_pre_restore(int platform_mode)
 {
 	return (platform_mode && hibernation_ops) ?
@@ -182,12 +188,15 @@ static int platform_pre_restore(int plat
 }
 
 /**
- *	platform_restore_cleanup - switch the platform to the normal mode of
- *	operation after a failing restore.  If platform_pre_restore() has been
- *	called before the failing restore, this function must be called too,
- *	regardless of the result of platform_pre_restore().
+ * platform_restore_cleanup - Switch to the working state after failing restore.
+ *
+ * Use the platform driver to switch the system to the normal mode of operation
+ * after a failing restore.
+ *
+ * If platform_pre_restore() has been called before the failing restore, this
+ * function must be called too, regardless of the result of
+ * platform_pre_restore().
  */
-
 static void platform_restore_cleanup(int platform_mode)
 {
 	if (platform_mode && hibernation_ops)
@@ -195,10 +204,8 @@ static void platform_restore_cleanup(int
 }
 
 /**
- *	platform_recover - recover the platform from a failure to suspend
- *	devices.
+ * platform_recover - Recover the platform from a failure to suspend devices.
  */
-
 static void platform_recover(int platform_mode)
 {
 	if (platform_mode && hibernation_ops && hibernation_ops->recover)
@@ -206,13 +213,12 @@ static void platform_recover(int platfor
 }
 
 /**
- *	swsusp_show_speed - print the time elapsed between two events.
- *	@start: Starting event.
- *	@stop: Final event.
- *	@nr_pages -	number of pages processed between @start and @stop
- *	@msg -		introductory message to print
+ * swsusp_show_speed - Print time elapsed between two events during hibernation.
+ * @start: Starting event.
+ * @stop: Final event.
+ * @nr_pages: Number of memory pages processed between @start and @stop.
+ * @msg: Additional diagnostic message to print.
  */
-
 void swsusp_show_speed(struct timeval *start, struct timeval *stop,
 			unsigned nr_pages, char *msg)
 {
@@ -235,11 +241,13 @@ void swsusp_show_speed(struct timeval *s
 }
 
 /**
- *	create_image - freeze devices that need to be frozen with interrupts
- *	off, create the hibernation image and thaw those devices.  Control
- *	reappears in this routine after a restore.
+ * create_image - Create a hibernation image.
+ *
+ * Execute device drivers' .freeze_noirq() callbacks, create a hibernation image
+ * and execute the drivers' .thaw_noirq() callbacks.
+ *
+ * Control reappears in this routine after the subsequent restore.
  */
-
 static int create_image(int platform_mode)
 {
 	int error;
@@ -304,14 +312,11 @@ static int create_image(int platform_mod
 }
 
 /**
- *	hibernation_snapshot - quiesce devices and create the hibernation
- *	snapshot image.
- *	@platform_mode - if set, use the platform driver, if available, to
- *			 prepare the platform firmware for the power transition.
+ * hibernation_snapshot - Quiesce devices and create a hibernation image.
+ * @platform_mode: If set, use platform driver to prepare for the transition.
  *
- *	Must be called with pm_mutex held
+ * This routine must be called with pm_mutex held.
  */
-
 int hibernation_snapshot(int platform_mode)
 {
 	pm_message_t msg = PMSG_RECOVER;
@@ -371,13 +376,13 @@ int hibernation_snapshot(int platform_mo
 }
 
 /**
- *	resume_target_kernel - prepare devices that need to be suspended with
- *	interrupts off, restore the contents of highmem that have not been
- *	restored yet from the image and run the low level code that will restore
- *	the remaining contents of memory and switch to the just restored target
- *	kernel.
+ * resume_target_kernel - Restore system state from a hibernation image.
+ *
+ * Execute device drivers' .freeze_noirq() callbacks, restore the contents of
+ * highmem that have not been restored yet from the image and run the low-level
+ * code that will restore the remaining contents of memory and switch to the
+ * just restored target kernel.
  */
-
 static int resume_target_kernel(bool platform_mode)
 {
 	int error;
@@ -445,14 +450,12 @@ static int resume_target_kernel(bool pla
 }
 
 /**
- *	hibernation_restore - quiesce devices and restore the hibernation
- *	snapshot image.  If successful, control returns in hibernation_snaphot()
- *	@platform_mode - if set, use the platform driver, if available, to
- *			 prepare the platform firmware for the transition.
+ * hibernation_restore - Quiesce devices and restore from a hibernation image.
+ * @platform_mode: If set, use platform driver to prepare for the transition.
  *
- *	Must be called with pm_mutex held
+ * This routine must be called with pm_mutex held.  If it is successful, control
+ * reappears in the restored target kernel in hibernation_snaphot().
  */
-
 int hibernation_restore(int platform_mode)
 {
 	int error;
@@ -472,10 +475,8 @@ int hibernation_restore(int platform_mod
 }
 
 /**
- *	hibernation_platform_enter - enter the hibernation state using the
- *	platform driver (if available)
+ * hibernation_platform_enter - Power off the system using the platform driver.
  */
-
 int hibernation_platform_enter(void)
 {
 	int error;
@@ -546,12 +547,12 @@ int hibernation_platform_enter(void)
 }
 
 /**
- *	power_down - Shut the machine down for hibernation.
+ * power_down - Shut the machine down for hibernation.
  *
- *	Use the platform driver, if configured so; otherwise try
- *	to power off or reboot.
+ * Use the platform driver, if configured, to put the system into the sleep
+ * state corresponding to hibernation, or try to power it off or reboot,
+ * depending on the value of hibernation_mode.
  */
-
 static void power_down(void)
 {
 	switch (hibernation_mode) {
@@ -588,9 +589,8 @@ static int prepare_processes(void)
 }
 
 /**
- *	hibernate - The granpappy of the built-in hibernation management
+ * hibernate - Carry out system hibernation, including saving the image.
  */
-
 int hibernate(void)
 {
 	int error;
@@ -668,17 +668,20 @@ int hibernate(void)
 
 
 /**
- *	software_resume - Resume from a saved image.
+ * software_resume - Resume from a saved hibernation image.
+ *
+ * This routine is called as a late initcall, when all devices have been
+ * discovered and initialized already.
  *
- *	Called as a late_initcall (so all devices are discovered and
- *	initialized), we call swsusp to see if we have a saved image or not.
- *	If so, we quiesce devices, the restore the saved image. We will
- *	return above (in hibernate() ) if everything goes well.
- *	Otherwise, we fail gracefully and return to the normally
- *	scheduled program.
+ * The image reading code is called to see if there is a hibernation image
+ * available for reading.  If that is the case, devices are quiesced and the
+ * contents of memory is restored from the saved image.
  *
+ * If this is successful, control reappears in the restored target kernel in
+ * hibernation_snaphot() which returns to hibernate().  Otherwise, the routine
+ * attempts to recover gracefully and make the kernel return to the normal mode
+ * of operation.
  */
-
 static int software_resume(void)
 {
 	int error;
@@ -808,21 +811,17 @@ static const char * const hibernation_mo
 	[HIBERNATION_TESTPROC]	= "testproc",
 };
 
-/**
- *	disk - Control hibernation mode
+/*
+ * /sys/power/disk - Control hibernation mode.
  *
- *	Suspend-to-disk can be handled in several ways. We have a few options
- *	for putting the system to sleep - using the platform driver (e.g. ACPI
- *	or other hibernation_ops), powering off the system or rebooting the
- *	system (for testing) as well as the two test modes.
- *
- *	The system can support 'platform', and that is known a priori (and
- *	encoded by the presence of hibernation_ops). However, the user may
- *	choose 'shutdown' or 'reboot' as alternatives, as well as one fo the
- *	test modes, 'test' or 'testproc'.
+ * Hibernation can be handled in several ways.  There are a few different ways
+ * to put the system into the sleep state: using the platform driver (e.g. ACPI
+ * or other hibernation_ops), powering it off or rebooting it (for testing
+ * mostly), or using one of the two available test modes.
  *
- *	show() will display what the mode is currently set to.
- *	store() will accept one of
+ * The sysfs file /sys/power/disk provides an interface for selecting the
+ * hibernation mode to use.  Reading from this file causes the available modes
+ * to be printed.  There are 5 modes that can be supported:
  *
  *	'platform'
  *	'shutdown'
@@ -830,8 +829,14 @@ static const char * const hibernation_mo
  *	'test'
  *	'testproc'
  *
- *	It will only change to 'platform' if the system
- *	supports it (as determined by having hibernation_ops).
+ * If a platform hibernation driver is in use, 'platform' will be supported
+ * and will be used by default.  Otherwise, 'shutdown' will be used by default.
+ * The selected option (i.e. the one corresponding to the current value of
+ * hibernation_mode) is enclosed by a square bracket.
+ *
+ * To select a given hibernation mode it is necessary to write the mode's
+ * string representation (as returned by reading from /sys/power/disk) back
+ * into /sys/power/disk.
  */
 
 static ssize_t disk_show(struct kobject *kobj, struct kobj_attribute *attr,
@@ -864,7 +869,6 @@ static ssize_t disk_show(struct kobject
 	return buf-start;
 }
 
-
 static ssize_t disk_store(struct kobject *kobj, struct kobj_attribute *attr,
 			  const char *buf, size_t n)
 {

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