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-rw-r--r--drivers/char/Makefile2
-rw-r--r--drivers/char/apm-emulation.c672
-rw-r--r--include/linux/apm-emulation.h62
-rw-r--r--kernel/power/Kconfig26
4 files changed, 762 insertions, 0 deletions
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 0326ca1a848..ae8567cc529 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -60,6 +60,8 @@ obj-$(CONFIG_BRIQ_PANEL) += briq_panel.o
obj-$(CONFIG_PRINTER) += lp.o
obj-$(CONFIG_TIPAR) += tipar.o
+obj-$(CONFIG_APM_EMULATION) += apm-emulation.o
+
obj-$(CONFIG_DTLK) += dtlk.o
obj-$(CONFIG_R3964) += n_r3964.o
obj-$(CONFIG_APPLICOM) += applicom.o
diff --git a/drivers/char/apm-emulation.c b/drivers/char/apm-emulation.c
new file mode 100644
index 00000000000..179c7a3b6e7
--- /dev/null
+++ b/drivers/char/apm-emulation.c
@@ -0,0 +1,672 @@
+/*
+ * bios-less APM driver for ARM Linux
+ * Jamey Hicks <jamey@crl.dec.com>
+ * adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)
+ *
+ * APM 1.2 Reference:
+ * Intel Corporation, Microsoft Corporation. Advanced Power Management
+ * (APM) BIOS Interface Specification, Revision 1.2, February 1996.
+ *
+ * [This document is available from Microsoft at:
+ * http://www.microsoft.com/hwdev/busbios/amp_12.htm]
+ */
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/miscdevice.h>
+#include <linux/apm_bios.h>
+#include <linux/capability.h>
+#include <linux/sched.h>
+#include <linux/pm.h>
+#include <linux/apm-emulation.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/init.h>
+#include <linux/completion.h>
+#include <linux/kthread.h>
+#include <linux/delay.h>
+
+#include <asm/system.h>
+
+/*
+ * The apm_bios device is one of the misc char devices.
+ * This is its minor number.
+ */
+#define APM_MINOR_DEV 134
+
+/*
+ * See Documentation/Config.help for the configuration options.
+ *
+ * Various options can be changed at boot time as follows:
+ * (We allow underscores for compatibility with the modules code)
+ * apm=on/off enable/disable APM
+ */
+
+/*
+ * Maximum number of events stored
+ */
+#define APM_MAX_EVENTS 16
+
+struct apm_queue {
+ unsigned int event_head;
+ unsigned int event_tail;
+ apm_event_t events[APM_MAX_EVENTS];
+};
+
+/*
+ * The per-file APM data
+ */
+struct apm_user {
+ struct list_head list;
+
+ unsigned int suser: 1;
+ unsigned int writer: 1;
+ unsigned int reader: 1;
+
+ int suspend_result;
+ unsigned int suspend_state;
+#define SUSPEND_NONE 0 /* no suspend pending */
+#define SUSPEND_PENDING 1 /* suspend pending read */
+#define SUSPEND_READ 2 /* suspend read, pending ack */
+#define SUSPEND_ACKED 3 /* suspend acked */
+#define SUSPEND_WAIT 4 /* waiting for suspend */
+#define SUSPEND_DONE 5 /* suspend completed */
+
+ struct apm_queue queue;
+};
+
+/*
+ * Local variables
+ */
+static int suspends_pending;
+static int apm_disabled;
+static struct task_struct *kapmd_tsk;
+
+static DECLARE_WAIT_QUEUE_HEAD(apm_waitqueue);
+static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);
+
+/*
+ * This is a list of everyone who has opened /dev/apm_bios
+ */
+static DECLARE_RWSEM(user_list_lock);
+static LIST_HEAD(apm_user_list);
+
+/*
+ * kapmd info. kapmd provides us a process context to handle
+ * "APM" events within - specifically necessary if we're going
+ * to be suspending the system.
+ */
+static DECLARE_WAIT_QUEUE_HEAD(kapmd_wait);
+static DEFINE_SPINLOCK(kapmd_queue_lock);
+static struct apm_queue kapmd_queue;
+
+static DEFINE_MUTEX(state_lock);
+
+static const char driver_version[] = "1.13"; /* no spaces */
+
+
+
+/*
+ * Compatibility cruft until the IPAQ people move over to the new
+ * interface.
+ */
+static void __apm_get_power_status(struct apm_power_info *info)
+{
+}
+
+/*
+ * This allows machines to provide their own "apm get power status" function.
+ */
+void (*apm_get_power_status)(struct apm_power_info *) = __apm_get_power_status;
+EXPORT_SYMBOL(apm_get_power_status);
+
+
+/*
+ * APM event queue management.
+ */
+static inline int queue_empty(struct apm_queue *q)
+{
+ return q->event_head == q->event_tail;
+}
+
+static inline apm_event_t queue_get_event(struct apm_queue *q)
+{
+ q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
+ return q->events[q->event_tail];
+}
+
+static void queue_add_event(struct apm_queue *q, apm_event_t event)
+{
+ q->event_head = (q->event_head + 1) % APM_MAX_EVENTS;
+ if (q->event_head == q->event_tail) {
+ static int notified;
+
+ if (notified++ == 0)
+ printk(KERN_ERR "apm: an event queue overflowed\n");
+ q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
+ }
+ q->events[q->event_head] = event;
+}
+
+static void queue_event(apm_event_t event)
+{
+ struct apm_user *as;
+
+ down_read(&user_list_lock);
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->reader)
+ queue_add_event(&as->queue, event);
+ }
+ up_read(&user_list_lock);
+ wake_up_interruptible(&apm_waitqueue);
+}
+
+/*
+ * queue_suspend_event - queue an APM suspend event.
+ *
+ * Check that we're in a state where we can suspend. If not,
+ * return -EBUSY. Otherwise, queue an event to all "writer"
+ * users. If there are no "writer" users, return '1' to
+ * indicate that we can immediately suspend.
+ */
+static int queue_suspend_event(apm_event_t event, struct apm_user *sender)
+{
+ struct apm_user *as;
+ int ret = 1;
+
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+
+ /*
+ * If a thread is still processing, we can't suspend, so reject
+ * the request.
+ */
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as != sender && as->reader && as->writer && as->suser &&
+ as->suspend_state != SUSPEND_NONE) {
+ ret = -EBUSY;
+ goto out;
+ }
+ }
+
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as != sender && as->reader && as->writer && as->suser) {
+ as->suspend_state = SUSPEND_PENDING;
+ suspends_pending++;
+ queue_add_event(&as->queue, event);
+ ret = 0;
+ }
+ }
+ out:
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+ wake_up_interruptible(&apm_waitqueue);
+ return ret;
+}
+
+static void apm_suspend(void)
+{
+ struct apm_user *as;
+ int err = pm_suspend(PM_SUSPEND_MEM);
+
+ /*
+ * Anyone on the APM queues will think we're still suspended.
+ * Send a message so everyone knows we're now awake again.
+ */
+ queue_event(APM_NORMAL_RESUME);
+
+ /*
+ * Finally, wake up anyone who is sleeping on the suspend.
+ */
+ mutex_lock(&state_lock);
+ down_read(&user_list_lock);
+ list_for_each_entry(as, &apm_user_list, list) {
+ if (as->suspend_state == SUSPEND_WAIT ||
+ as->suspend_state == SUSPEND_ACKED) {
+ as->suspend_result = err;
+ as->suspend_state = SUSPEND_DONE;
+ }
+ }
+ up_read(&user_list_lock);
+ mutex_unlock(&state_lock);
+
+ wake_up(&apm_suspend_waitqueue);
+}
+
+static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
+{
+ struct apm_user *as = fp->private_data;
+ apm_event_t event;
+ int i = count, ret = 0;
+
+ if (count < sizeof(apm_event_t))
+ return -EINVAL;
+
+ if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
+ return -EAGAIN;
+
+ wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));
+
+ while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
+ event = queue_get_event(&as->queue);
+
+ ret = -EFAULT;
+ if (copy_to_user(buf, &event, sizeof(event)))
+ break;
+
+ mutex_lock(&state_lock);
+ if (as->suspend_state == SUSPEND_PENDING &&
+ (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND))
+ as->suspend_state = SUSPEND_READ;
+ mutex_unlock(&state_lock);
+
+ buf += sizeof(event);
+ i -= sizeof(event);
+ }
+
+ if (i < count)
+ ret = count - i;
+
+ return ret;
+}
+
+static unsigned int apm_poll(struct file *fp, poll_table * wait)
+{
+ struct apm_user *as = fp->private_data;
+
+ poll_wait(fp, &apm_waitqueue, wait);
+ return queue_empty(&as->queue) ? 0 : POLLIN | POLLRDNORM;
+}
+
+/*
+ * apm_ioctl - handle APM ioctl
+ *
+ * APM_IOC_SUSPEND
+ * This IOCTL is overloaded, and performs two functions. It is used to:
+ * - initiate a suspend
+ * - acknowledge a suspend read from /dev/apm_bios.
+ * Only when everyone who has opened /dev/apm_bios with write permission
+ * has acknowledge does the actual suspend happen.
+ */
+static int
+apm_ioctl(struct inode * inode, struct file *filp, u_int cmd, u_long arg)
+{
+ struct apm_user *as = filp->private_data;
+ unsigned long flags;
+ int err = -EINVAL;
+
+ if (!as->suser || !as->writer)
+ return -EPERM;
+
+ switch (cmd) {
+ case APM_IOC_SUSPEND:
+ mutex_lock(&state_lock);
+
+ as->suspend_result = -EINTR;
+
+ if (as->suspend_state == SUSPEND_READ) {
+ int pending;
+
+ /*
+ * If we read a suspend command from /dev/apm_bios,
+ * then the corresponding APM_IOC_SUSPEND ioctl is
+ * interpreted as an acknowledge.
+ */
+ as->suspend_state = SUSPEND_ACKED;
+ suspends_pending--;
+ pending = suspends_pending == 0;
+ mutex_unlock(&state_lock);
+
+ /*
+ * If there are no further acknowledges required,
+ * suspend the system.
+ */
+ if (pending)
+ apm_suspend();
+
+ /*
+ * Wait for the suspend/resume to complete. If there
+ * are pending acknowledges, we wait here for them.
+ *
+ * Note: we need to ensure that the PM subsystem does
+ * not kick us out of the wait when it suspends the
+ * threads.
+ */
+ flags = current->flags;
+ current->flags |= PF_NOFREEZE;
+
+ wait_event(apm_suspend_waitqueue,
+ as->suspend_state == SUSPEND_DONE);
+ } else {
+ as->suspend_state = SUSPEND_WAIT;
+ mutex_unlock(&state_lock);
+
+ /*
+ * Otherwise it is a request to suspend the system.
+ * Queue an event for all readers, and expect an
+ * acknowledge from all writers who haven't already
+ * acknowledged.
+ */
+ err = queue_suspend_event(APM_USER_SUSPEND, as);
+ if (err < 0) {
+ /*
+ * Avoid taking the lock here - this
+ * should be fine.
+ */
+ as->suspend_state = SUSPEND_NONE;
+ break;
+ }
+
+ if (err > 0)
+ apm_suspend();
+
+ /*
+ * Wait for the suspend/resume to complete. If there
+ * are pending acknowledges, we wait here for them.
+ *
+ * Note: we need to ensure that the PM subsystem does
+ * not kick us out of the wait when it suspends the
+ * threads.
+ */
+ flags = current->flags;
+ current->flags |= PF_NOFREEZE;
+
+ wait_event_interruptible(apm_suspend_waitqueue,
+ as->suspend_state == SUSPEND_DONE);
+ }
+
+ current->flags = flags;
+
+ mutex_lock(&state_lock);
+ err = as->suspend_result;
+ as->suspend_state = SUSPEND_NONE;
+ mutex_unlock(&state_lock);
+ break;
+ }
+
+ return err;
+}
+
+static int apm_release(struct inode * inode, struct file * filp)
+{
+ struct apm_user *as = filp->private_data;
+ int pending = 0;
+
+ filp->private_data = NULL;
+
+ down_write(&user_list_lock);
+ list_del(&as->list);
+ up_write(&user_list_lock);
+
+ /*
+ * We are now unhooked from the chain. As far as new
+ * events are concerned, we no longer exist. However, we
+ * need to balance suspends_pending, which means the
+ * possibility of sleeping.
+ */
+ mutex_lock(&state_lock);
+ if (as->suspend_state != SUSPEND_NONE) {
+ suspends_pending -= 1;
+ pending = suspends_pending == 0;
+ }
+ mutex_unlock(&state_lock);
+ if (pending)
+ apm_suspend();
+
+ kfree(as);
+ return 0;
+}
+
+static int apm_open(struct inode * inode, struct file * filp)
+{
+ struct apm_user *as;
+
+ as = kzalloc(sizeof(*as), GFP_KERNEL);
+ if (as) {
+ /*
+ * XXX - this is a tiny bit broken, when we consider BSD
+ * process accounting. If the device is opened by root, we
+ * instantly flag that we used superuser privs. Who knows,
+ * we might close the device immediately without doing a
+ * privileged operation -- cevans
+ */
+ as->suser = capable(CAP_SYS_ADMIN);
+ as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
+ as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;
+
+ down_write(&user_list_lock);
+ list_add(&as->list, &apm_user_list);
+ up_write(&user_list_lock);
+
+ filp->private_data = as;
+ }
+
+ return as ? 0 : -ENOMEM;
+}
+
+static struct file_operations apm_bios_fops = {
+ .owner = THIS_MODULE,
+ .read = apm_read,
+ .poll = apm_poll,
+ .ioctl = apm_ioctl,
+ .open = apm_open,
+ .release = apm_release,
+};
+
+static struct miscdevice apm_device = {
+ .minor = APM_MINOR_DEV,
+ .name = "apm_bios",
+ .fops = &apm_bios_fops
+};
+
+
+#ifdef CONFIG_PROC_FS
+/*
+ * Arguments, with symbols from linux/apm_bios.h.
+ *
+ * 0) Linux driver version (this will change if format changes)
+ * 1) APM BIOS Version. Usually 1.0, 1.1 or 1.2.
+ * 2) APM flags from APM Installation Check (0x00):
+ * bit 0: APM_16_BIT_SUPPORT
+ * bit 1: APM_32_BIT_SUPPORT
+ * bit 2: APM_IDLE_SLOWS_CLOCK
+ * bit 3: APM_BIOS_DISABLED
+ * bit 4: APM_BIOS_DISENGAGED
+ * 3) AC line status
+ * 0x00: Off-line
+ * 0x01: On-line
+ * 0x02: On backup power (BIOS >= 1.1 only)
+ * 0xff: Unknown
+ * 4) Battery status
+ * 0x00: High
+ * 0x01: Low
+ * 0x02: Critical
+ * 0x03: Charging
+ * 0x04: Selected battery not present (BIOS >= 1.2 only)
+ * 0xff: Unknown
+ * 5) Battery flag
+ * bit 0: High
+ * bit 1: Low
+ * bit 2: Critical
+ * bit 3: Charging
+ * bit 7: No system battery
+ * 0xff: Unknown
+ * 6) Remaining battery life (percentage of charge):
+ * 0-100: valid
+ * -1: Unknown
+ * 7) Remaining battery life (time units):
+ * Number of remaining minutes or seconds
+ * -1: Unknown
+ * 8) min = minutes; sec = seconds
+ */
+static int apm_get_info(char *buf, char **start, off_t fpos, int length)
+{
+ struct apm_power_info info;
+ char *units;
+ int ret;
+
+ info.ac_line_status = 0xff;
+ info.battery_status = 0xff;
+ info.battery_flag = 0xff;
+ info.battery_life = -1;
+ info.time = -1;
+ info.units = -1;
+
+ if (apm_get_power_status)
+ apm_get_power_status(&info);
+
+ switch (info.units) {
+ default: units = "?"; break;
+ case 0: units = "min"; break;
+ case 1: units = "sec"; break;
+ }
+
+ ret = sprintf(buf, "%s 1.2 0x%02x 0x%02x 0x%02x 0x%02x %d%% %d %s\n",
+ driver_version, APM_32_BIT_SUPPORT,
+ info.ac_line_status, info.battery_status,
+ info.battery_flag, info.battery_life,
+ info.time, units);
+
+ return ret;
+}
+#endif
+
+static int kapmd(void *arg)
+{
+ do {
+ apm_event_t event;
+ int ret;
+
+ wait_event_interruptible(kapmd_wait,
+ !queue_empty(&kapmd_queue) || kthread_should_stop());
+
+ if (kthread_should_stop())
+ break;
+
+ spin_lock_irq(&kapmd_queue_lock);
+ event = 0;
+ if (!queue_empty(&kapmd_queue))
+ event = queue_get_event(&kapmd_queue);
+ spin_unlock_irq(&kapmd_queue_lock);
+
+ switch (event) {
+ case 0:
+ break;
+
+ case APM_LOW_BATTERY:
+ case APM_POWER_STATUS_CHANGE:
+ queue_event(event);
+ break;
+
+ case APM_USER_SUSPEND:
+ case APM_SYS_SUSPEND:
+ ret = queue_suspend_event(event, NULL);
+ if (ret < 0) {
+ /*
+ * We were busy. Try again in 50ms.
+ */
+ queue_add_event(&kapmd_queue, event);
+ msleep(50);
+ }
+ if (ret > 0)
+ apm_suspend();
+ break;
+
+ case APM_CRITICAL_SUSPEND:
+ apm_suspend();
+ break;
+ }
+ } while (1);
+
+ return 0;
+}
+
+static int __init apm_init(void)
+{
+ int ret;
+
+ if (apm_disabled) {
+ printk(KERN_NOTICE "apm: disabled on user request.\n");
+ return -ENODEV;
+ }
+
+ kapmd_tsk = kthread_create(kapmd, NULL, "kapmd");
+ if (IS_ERR(kapmd_tsk)) {
+ ret = PTR_ERR(kapmd_tsk);
+ kapmd_tsk = NULL;
+ return ret;
+ }
+ kapmd_tsk->flags |= PF_NOFREEZE;
+ wake_up_process(kapmd_tsk);
+
+#ifdef CONFIG_PROC_FS
+ create_proc_info_entry("apm", 0, NULL, apm_get_info);
+#endif
+
+ ret = misc_register(&apm_device);
+ if (ret != 0) {
+ remove_proc_entry("apm", NULL);
+ kthread_stop(kapmd_tsk);
+ }
+
+ return ret;
+}
+
+static void __exit apm_exit(void)
+{
+ misc_deregister(&apm_device);
+ remove_proc_entry("apm", NULL);
+
+ kthread_stop(kapmd_tsk);
+}
+
+module_init(apm_init);
+module_exit(apm_exit);
+
+MODULE_AUTHOR("Stephen Rothwell");
+MODULE_DESCRIPTION("Advanced Power Management");
+MODULE_LICENSE("GPL");
+
+#ifndef MODULE
+static int __init apm_setup(char *str)
+{
+ while ((str != NULL) && (*str != '\0')) {
+ if (strncmp(str, "off", 3) == 0)
+ apm_disabled = 1;
+ if (strncmp(str, "on", 2) == 0)
+ apm_disabled = 0;
+ str = strchr(str, ',');
+ if (str != NULL)
+ str += strspn(str, ", \t");
+ }
+ return 1;
+}
+
+__setup("apm=", apm_setup);
+#endif
+
+/**
+ * apm_queue_event - queue an APM event for kapmd
+ * @event: APM event
+ *
+ * Queue an APM event for kapmd to process and ultimately take the
+ * appropriate action. Only a subset of events are handled:
+ * %APM_LOW_BATTERY
+ * %APM_POWER_STATUS_CHANGE
+ * %APM_USER_SUSPEND
+ * %APM_SYS_SUSPEND
+ * %APM_CRITICAL_SUSPEND
+ */
+void apm_queue_event(apm_event_t event)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&kapmd_queue_lock, flags);
+ queue_add_event(&kapmd_queue, event);
+ spin_unlock_irqrestore(&kapmd_queue_lock, flags);
+
+ wake_up_interruptible(&kapmd_wait);
+}
+EXPORT_SYMBOL(apm_queue_event);
diff --git a/include/linux/apm-emulation.h b/include/linux/apm-emulation.h
new file mode 100644
index 00000000000..e6d800358dd
--- /dev/null
+++ b/include/linux/apm-emulation.h
@@ -0,0 +1,62 @@
+/* -*- linux-c -*-
+ *
+ * (C) 2003 zecke@handhelds.org
+ *
+ * GPL version 2
+ *
+ * based on arch/arm/kernel/apm.c
+ * factor out the information needed by architectures to provide
+ * apm status
+ */
+#ifndef __LINUX_APM_EMULATION_H
+#define __LINUX_APM_EMULATION_H
+
+#include <linux/apm_bios.h>
+
+/*
+ * This structure gets filled in by the machine specific 'get_power_status'
+ * implementation. Any fields which are not set default to a safe value.
+ */
+struct apm_power_info {
+ unsigned char ac_line_status;
+#define APM_AC_OFFLINE 0
+#define APM_AC_ONLINE 1
+#define APM_AC_BACKUP 2
+#define APM_AC_UNKNOWN 0xff
+
+ unsigned char battery_status;
+#define APM_BATTERY_STATUS_HIGH 0
+#define APM_BATTERY_STATUS_LOW 1
+#define APM_BATTERY_STATUS_CRITICAL 2
+#define APM_BATTERY_STATUS_CHARGING 3
+#define APM_BATTERY_STATUS_NOT_PRESENT 4
+#define APM_BATTERY_STATUS_UNKNOWN 0xff
+
+ unsigned char battery_flag;
+#define APM_BATTERY_FLAG_HIGH (1 << 0)
+#define APM_BATTERY_FLAG_LOW (1 << 1)
+#define APM_BATTERY_FLAG_CRITICAL (1 << 2)
+#define APM_BATTERY_FLAG_CHARGING (1 << 3)
+#define APM_BATTERY_FLAG_NOT_PRESENT (1 << 7)
+#define APM_BATTERY_FLAG_UNKNOWN 0xff
+
+ int battery_life;
+ int time;
+ int units;
+#define APM_UNITS_MINS 0
+#define APM_UNITS_SECS 1
+#define APM_UNITS_UNKNOWN -1
+
+};
+
+/*
+ * This allows machines to provide their own "apm get power status" function.
+ */
+extern void (*apm_get_power_status)(struct apm_power_info *);
+
+/*
+ * Queue an event (APM_SYS_SUSPEND or APM_CRITICAL_SUSPEND)
+ */
+void apm_queue_event(apm_event_t event);
+
+#endif /* __LINUX_APM_EMULATION_H */
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index ed296225dcd..95f6657fff7 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -131,3 +131,29 @@ config SUSPEND_SMP
bool
depends on HOTPLUG_CPU && X86 && PM
default y
+
+config APM_EMULATION
+ tristate "Advanced Power Management Emulation"
+ depends on PM && SYS_SUPPORTS_APM_EMULATION
+ help
+ APM is a BIOS specification for saving power using several different
+ techniques. This is mostly useful for battery powered laptops with
+ APM compliant BIOSes. If you say Y here, the system time will be
+ reset after a RESUME operation, the /proc/apm device will provide
+ battery status information, and user-space programs will receive
+ notification of APM "events" (e.g. battery status change).
+
+ In order to use APM, you will need supporting software. For location
+ and more information, read <file:Documentation/pm.txt> and the
+ Battery Powered Linux mini-HOWTO, available from
+ <http://www.tldp.org/docs.html#howto>.
+
+ This driver does not spin down disk drives (see the hdparm(8)
+ manpage ("man 8 hdparm") for that), and it doesn't turn off
+ VESA-compliant "green" monitors.
+
+ Generally, if you don't have a battery in your machine, there isn't
+ much point in using this driver and you should say N. If you get
+ random kernel OOPSes or reboots that don't seem to be related to
+ anything, try disabling/enabling this option (or disabling/enabling
+ APM in your BIOS).
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-25 21:40:55 +0000