From 2ca6f62f595c01f689b269db6736de5544da7667 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 18 Apr 2011 23:58:59 +0200 Subject: PM: Fix error code paths executed after failing syscore_suspend() If syscore_suspend() fails in suspend_enter(), create_image() or resume_target_kernel(), it is necessary to call sysdev_resume(), because sysdev_suspend() has been called already and succeeded and we are going to abort the transition. Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman --- kernel/power/hibernate.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index aeabd26e3342..50aae660174d 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -273,8 +273,11 @@ static int create_image(int platform_mode) local_irq_disable(); error = sysdev_suspend(PMSG_FREEZE); - if (!error) + if (!error) { error = syscore_suspend(); + if (error) + sysdev_resume(); + } if (error) { printk(KERN_ERR "PM: Some system devices failed to power down, " "aborting hibernation\n"); @@ -407,8 +410,11 @@ static int resume_target_kernel(bool platform_mode) local_irq_disable(); error = sysdev_suspend(PMSG_QUIESCE); - if (!error) + if (!error) { error = syscore_suspend(); + if (error) + sysdev_resume(); + } if (error) goto Enable_irqs; -- cgit v1.2.3 From 2e711c04dbbf7a7732a3f7073b1fc285d12b369d Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 26 Apr 2011 19:15:07 +0200 Subject: PM: Remove sysdev suspend, resume and shutdown operations Since suspend, resume and shutdown operations in struct sysdev_class and struct sysdev_driver are not used any more, remove them. Also drop sysdev_suspend(), sysdev_resume() and sysdev_shutdown() used for executing those operations and modify all of their users accordingly. This reduces kernel code size quite a bit and reduces its complexity. Signed-off-by: Rafael J. Wysocki Acked-by: Greg Kroah-Hartman --- kernel/power/hibernate.c | 18 ++---------------- 1 file changed, 2 insertions(+), 16 deletions(-) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index 50aae660174d..554d3b049f35 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -272,12 +272,7 @@ static int create_image(int platform_mode) local_irq_disable(); - error = sysdev_suspend(PMSG_FREEZE); - if (!error) { - error = syscore_suspend(); - if (error) - sysdev_resume(); - } + error = syscore_suspend(); if (error) { printk(KERN_ERR "PM: Some system devices failed to power down, " "aborting hibernation\n"); @@ -302,7 +297,6 @@ static int create_image(int platform_mode) Power_up: syscore_resume(); - sysdev_resume(); /* NOTE: dpm_resume_noirq() is just a resume() for devices * that suspended with irqs off ... no overall powerup. */ @@ -409,12 +403,7 @@ static int resume_target_kernel(bool platform_mode) local_irq_disable(); - error = sysdev_suspend(PMSG_QUIESCE); - if (!error) { - error = syscore_suspend(); - if (error) - sysdev_resume(); - } + error = syscore_suspend(); if (error) goto Enable_irqs; @@ -442,7 +431,6 @@ static int resume_target_kernel(bool platform_mode) touch_softlockup_watchdog(); syscore_resume(); - sysdev_resume(); Enable_irqs: local_irq_enable(); @@ -528,7 +516,6 @@ int hibernation_platform_enter(void) goto Platform_finish; local_irq_disable(); - sysdev_suspend(PMSG_HIBERNATE); syscore_suspend(); if (pm_wakeup_pending()) { error = -EAGAIN; @@ -541,7 +528,6 @@ int hibernation_platform_enter(void) Power_up: syscore_resume(); - sysdev_resume(); local_irq_enable(); enable_nonboot_cpus(); -- cgit v1.2.3 From ddeb648708108091a641adad0a438ec4fd8bf190 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sun, 15 May 2011 11:38:48 +0200 Subject: PM / Hibernate: Add sysfs knob to control size of memory for drivers Martin reports that on his system hibernation occasionally fails due to the lack of memory, because the radeon driver apparently allocates too much of it during the device freeze stage. It turns out that the amount of memory allocated by radeon during hibernation (and presumably during system suspend too) depends on the utilization of the GPU (e.g. hibernating while there are two KDE 4 sessions with compositing enabled causes radeon to allocate more memory than for one KDE 4 session). In principle it should be possible to use image_size to make the memory preallocation mechanism free enough memory for the radeon driver, but in practice it is not easy to guess the right value because of the way the preallocation code uses image_size. For this reason, it seems reasonable to allow users to control the amount of memory reserved for driver allocations made after the hibernate preallocation, which currently is constant and amounts to 1 MB. Introduce a new sysfs file, /sys/power/reserved_size, whose value will be used as the amount of memory to reserve for the post-preallocation reservations made by device drivers, in bytes. For backwards compatibility, set its default (and initial) value to the currently used number (1 MB). References: https://bugzilla.kernel.org/show_bug.cgi?id=34102 Reported-and-tested-by: Martin Steigerwald Signed-off-by: Rafael J. Wysocki --- kernel/power/hibernate.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index 50aae660174d..431721313b71 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -982,10 +982,33 @@ static ssize_t image_size_store(struct kobject *kobj, struct kobj_attribute *att power_attr(image_size); +static ssize_t reserved_size_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return sprintf(buf, "%lu\n", reserved_size); +} + +static ssize_t reserved_size_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t n) +{ + unsigned long size; + + if (sscanf(buf, "%lu", &size) == 1) { + reserved_size = size; + return n; + } + + return -EINVAL; +} + +power_attr(reserved_size); + static struct attribute * g[] = { &disk_attr.attr, &resume_attr.attr, &image_size_attr.attr, + &reserved_size_attr.attr, NULL, }; -- cgit v1.2.3 From 91e7c75ba93c48a82670d630b9daac92ff70095d Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 17 May 2011 23:26:00 +0200 Subject: PM: Allow drivers to allocate memory from .prepare() callbacks safely If device drivers allocate substantial amounts of memory (above 1 MB) in their hibernate .freeze() callbacks (or in their legacy suspend callbcks during hibernation), the subsequent creation of hibernate image may fail due to the lack of memory. This is the case, because the drivers' .freeze() callbacks are executed after the hibernate memory preallocation has been carried out and the preallocated amount of memory may be too small to cover the new driver allocations. Unfortunately, the drivers' .prepare() callbacks also are executed after the hibernate memory preallocation has completed, so they are not suitable for allocating additional memory either. Thus the only way a driver can safely allocate memory during hibernation is to use a hibernate/suspend notifier. However, the notifiers are called before the freezing of user space and the drivers wanting to use them for allocating additional memory may not know how much memory needs to be allocated at that point. To let device drivers overcome this difficulty rework the hibernation sequence so that the memory preallocation is carried out after the drivers' .prepare() callbacks have been executed, so that the .prepare() callbacks can be used for allocating additional memory to be used by the drivers' .freeze() callbacks. Update documentation to match the new behavior of the code. Signed-off-by: Rafael J. Wysocki --- kernel/power/hibernate.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index 95a2ac40f48c..f9bec56d8825 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -327,20 +327,25 @@ static int create_image(int platform_mode) int hibernation_snapshot(int platform_mode) { + pm_message_t msg = PMSG_RECOVER; int error; error = platform_begin(platform_mode); if (error) goto Close; + error = dpm_prepare(PMSG_FREEZE); + if (error) + goto Complete_devices; + /* Preallocate image memory before shutting down devices. */ error = hibernate_preallocate_memory(); if (error) - goto Close; + goto Complete_devices; suspend_console(); pm_restrict_gfp_mask(); - error = dpm_suspend_start(PMSG_FREEZE); + error = dpm_suspend(PMSG_FREEZE); if (error) goto Recover_platform; @@ -358,13 +363,17 @@ int hibernation_snapshot(int platform_mode) if (error || !in_suspend) swsusp_free(); - dpm_resume_end(in_suspend ? - (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE); + msg = in_suspend ? (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE; + dpm_resume(msg); if (error || !in_suspend) pm_restore_gfp_mask(); resume_console(); + + Complete_devices: + dpm_complete(msg); + Close: platform_end(platform_mode); return error; -- cgit v1.2.3 From 4e2d9491a78929badcf774869b458486acb96365 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 24 May 2011 00:21:26 +0200 Subject: PM / Hibernate: Update some comments in core hibernate code Some comments in the core hibernate code are outdated, some aren't necessary any more and at least one of them is plain wrong. Remove those comments or update them. Signed-off-by: Rafael J. Wysocki --- kernel/power/hibernate.c | 21 +++++++-------------- 1 file changed, 7 insertions(+), 14 deletions(-) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index f9bec56d8825..6418d8c8cdb2 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -248,12 +248,6 @@ static int create_image(int platform_mode) if (error) return error; - /* At this point, dpm_suspend_start() has been called, but *not* - * dpm_suspend_noirq(). We *must* call dpm_suspend_noirq() now. - * Otherwise, drivers for some devices (e.g. interrupt controllers) - * become desynchronized with the actual state of the hardware - * at resume time, and evil weirdness ensues. - */ error = dpm_suspend_noirq(PMSG_FREEZE); if (error) { printk(KERN_ERR "PM: Some devices failed to power down, " @@ -297,9 +291,6 @@ static int create_image(int platform_mode) Power_up: syscore_resume(); - /* NOTE: dpm_resume_noirq() is just a resume() for devices - * that suspended with irqs off ... no overall powerup. - */ Enable_irqs: local_irq_enable(); @@ -416,24 +407,26 @@ static int resume_target_kernel(bool platform_mode) if (error) goto Enable_irqs; - /* We'll ignore saved state, but this gets preempt count (etc) right */ save_processor_state(); error = restore_highmem(); if (!error) { error = swsusp_arch_resume(); /* * The code below is only ever reached in case of a failure. - * Otherwise execution continues at place where - * swsusp_arch_suspend() was called + * Otherwise, execution continues at the place where + * swsusp_arch_suspend() was called. */ BUG_ON(!error); - /* This call to restore_highmem() undos the previous one */ + /* + * This call to restore_highmem() reverts the changes made by + * the previous one. + */ restore_highmem(); } /* * The only reason why swsusp_arch_resume() can fail is memory being * very tight, so we have to free it as soon as we can to avoid - * subsequent failures + * subsequent failures. */ swsusp_free(); restore_processor_state(); -- cgit v1.2.3 From 354258011e8e86961f7a72ad154ca8caf0c4c6f7 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 24 May 2011 23:35:55 +0200 Subject: PM / Hibernate: Remove arch_prepare_suspend() All architectures supporting hibernation define arch_prepare_suspend() as an empty function, so remove it. Signed-off-by: Rafael J. Wysocki --- kernel/power/hibernate.c | 5 ----- 1 file changed, 5 deletions(-) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index 6418d8c8cdb2..16aa3bcd6b54 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -25,7 +25,6 @@ #include #include #include -#include #include "power.h" @@ -244,10 +243,6 @@ static int create_image(int platform_mode) { int error; - error = arch_prepare_suspend(); - if (error) - return error; - error = dpm_suspend_noirq(PMSG_FREEZE); if (error) { printk(KERN_ERR "PM: Some devices failed to power down, " -- cgit v1.2.3 From f42a9813fbf930fea3bdd0524dcb43c7feb0c977 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 24 May 2011 23:36:06 +0200 Subject: PM / Hibernate: Update kerneldoc comments in hibernate.c 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 Acked-by: Randy Dunlap --- kernel/power/hibernate.c | 194 +++++++++++++++++++++++++---------------------- 1 file changed, 104 insertions(+), 90 deletions(-) (limited to 'kernel/power/hibernate.c') diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c index 16aa3bcd6b54..8f7b1db1ece1 100644 --- a/kernel/power/hibernate.c +++ b/kernel/power/hibernate.c @@ -54,10 +54,9 @@ static int hibernation_mode = HIBERNATION_SHUTDOWN; 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 @@ -114,10 +113,9 @@ static int hibernation_test(int level) { return 0; } #endif /* !CONFIG_PM_DEBUG */ /** - * platform_begin - tell the platform driver that we're starting - * hibernation + * platform_begin - Call platform to start hibernation. + * @platform_mode: Whether or not to use the platform driver. */ - static int platform_begin(int platform_mode) { return (platform_mode && hibernation_ops) ? @@ -125,10 +123,9 @@ static int platform_begin(int platform_mode) } /** - * platform_end - tell the platform driver that we've entered the - * working state + * platform_end - Call platform to finish transition to the working state. + * @platform_mode: Whether or not to use the platform driver. */ - static void platform_end(int platform_mode) { if (platform_mode && hibernation_ops) @@ -136,8 +133,11 @@ static void platform_end(int platform_mode) } /** - * 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. + * @platform_mode: Whether or not to use the platform driver. + * + * 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) @@ -147,10 +147,14 @@ static int platform_pre_snapshot(int platform_mode) } /** - * platform_leave - prepare the machine for switching to the normal mode - * of operation using the platform driver (called with interrupts disabled) + * platform_leave - Call platform to prepare a transition to the working state. + * @platform_mode: Whether or not to use the platform driver. + * + * 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) @@ -158,10 +162,14 @@ static void platform_leave(int platform_mode) } /** - * platform_finish - switch the machine to the normal mode of operation - * using the platform driver (must be called after platform_prepare()) + * platform_finish - Call platform to switch the system to the working state. + * @platform_mode: Whether or not to use the platform driver. + * + * 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) @@ -169,11 +177,15 @@ static void platform_finish(int platform_mode) } /** - * 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. + * @platform_mode: Whether or not to use the platform driver. + * + * 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) ? @@ -181,12 +193,16 @@ static int platform_pre_restore(int platform_mode) } /** - * 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. + * @platform_mode: Whether or not to use the platform driver. + * + * 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) @@ -194,10 +210,9 @@ static void platform_restore_cleanup(int platform_mode) } /** - * platform_recover - recover the platform from a failure to suspend - * devices. + * platform_recover - Recover from a failure to suspend devices. + * @platform_mode: Whether or not to use the platform driver. */ - static void platform_recover(int platform_mode) { if (platform_mode && hibernation_ops && hibernation_ops->recover) @@ -205,13 +220,12 @@ static void platform_recover(int platform_mode) } /** - * 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) { @@ -234,11 +248,14 @@ void swsusp_show_speed(struct timeval *start, struct timeval *stop, } /** - * 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. + * @platform_mode: Whether or not to use the platform driver. + * + * 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; @@ -303,14 +320,11 @@ static int create_image(int platform_mode) } /** - * 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; @@ -370,13 +384,14 @@ int hibernation_snapshot(int platform_mode) } /** - * 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. + * @platform_mode: Whether or not to use the platform driver. + * + * 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; @@ -444,14 +459,12 @@ static int resume_target_kernel(bool platform_mode) } /** - * 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; @@ -471,10 +484,8 @@ int hibernation_restore(int platform_mode) } /** - * 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; @@ -545,12 +556,12 @@ 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) { @@ -587,9 +598,8 @@ 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; @@ -667,17 +677,20 @@ 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; @@ -807,21 +820,17 @@ static const char * const hibernation_modes[] = { [HIBERNATION_TESTPROC] = "testproc", }; -/** - * 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. +/* + * /sys/power/disk - Control hibernation mode. * - * 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' @@ -829,8 +838,14 @@ static const char * const hibernation_modes[] = { * '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, @@ -863,7 +878,6 @@ static ssize_t disk_show(struct kobject *kobj, struct kobj_attribute *attr, return buf-start; } - static ssize_t disk_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t n) { -- cgit v1.2.3