[PATCH 01/13] PM: Add wake lock api.

["Arve Hjønnevåg" <arve@android.com>]

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/power/wakelocks.txt |   91 ++++++++++++++++++++++++++++++++++++
 include/linux/wakelock.h          |   92 +++++++++++++++++++++++++++++++++++++
 2 files changed, 183 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/power/wakelocks.txt
 create mode 100755 include/linux/wakelock.h

diff --git a/Documentation/power/wakelocks.txt b/Documentation/power/wakelocks.txt
new file mode 100644
index 0000000..219bb11
--- /dev/null
+++ b/Documentation/power/wakelocks.txt
@@ -0,0 +1,91 @@
+Wakelocks
+=========
+
+A locked wakelock, depending on its type, prevents the system from entering
+suspend or other low-power states. When creating a wakelock, you can select
+if it prevents suspend or low-power idle states.  If the type is set to
+WAKE_LOCK_SUSPEND, the wakelock prevents a full system suspend. If the type
+is WAKE_LOCK_IDLE, low-power states that cause large interrupt latencies, or
+that disable a set of interrupts, will not be entered from idle until the
+wakelocks are released. Unless the type is specified, this document refers
+to wakelocks with the type set to WAKE_LOCK_SUSPEND.
+
+If the suspend operation has already started when locking a wakelock, it will
+abort the suspend operation as long it has not already reached the suspend_late
+stage. This means that locking a wakelock from an interrupt handler or a
+freezeable thread always works, but if you lock a wakelock from a suspend_late
+handler you must also return an error from that handler to abort suspend.
+
+Wakelocks can be used to allow user-space to decide which keys should wake the
+full system up and turn the screen on. Use set_irq_wake or a platform specific
+api to make sure the keypad interrupt wakes up the cpu. Once the keypad driver
+has resumed, the sequence of events can look like this:
+- The Keypad driver gets an interrupt. It then locks the keypad-scan wakelock
+  and starts scanning the keypad matrix.
+- The keypad-scan code detects a key change and reports it to the input-event
+  driver.
+- The input-event driver sees the key change, enqueues an event, and locks
+  the input-event-queue wakelock.
+- The keypad-scan code detects that no keys are held and unlocks the
+  keypad-scan wakelock.
+- The user-space input-event thread returns from select/poll, locks the
+  process-input-events wakelock and then calls read in the input-event device.
+- The input-event driver dequeues the key-event and, since the queue is now
+  empty, it unlocks the input-event-queue wakelock.
+- The user-space input-event thread returns from read. It determines that the
+  key should not wake up the full system, releases the process-input-events
+  wakelock and calls select or poll.
+
+                 Key pressed   Key released
+                     |             |
+keypad-scan          ++++++++++++++++++
+input-event-queue        +++          +++
+process-input-events       +++          +++
+
+
+Driver API
+==========
+
+A driver can use the wakelock api by adding a wakelock variable to its state
+and calling wake_lock_init. For instance:
+struct state {
+	struct wakelock wakelock;
+}
+
+init() {
+	wake_lock_init(&state->wakelock, WAKE_LOCK_SUSPEND, "wakelockname");
+}
+
+Before freeing the memory, wake_lock_destroy must be called:
+
+uninit() {
+	wake_lock_destroy(&state->wakelock);
+}
+
+When the driver determines that it needs to run (usually in an interrupt
+handler) it calls wake_lock:
+	wake_lock(&state->wakelock);
+
+When it no longer needs to run it calls wake_unlock:
+	wake_unlock(&state->wakelock);
+
+It can also call wake_lock_timeout to release the wakelock after a delay:
+	wake_lock_timeout(&state->wakelock, HZ);
+
+This works whether the wakelock is already held or not. It is useful if the
+driver woke up other parts of the system that do not use wakelocks but
+still need to run. Avoid this when possible, since it will waste power
+if the timeout is long or may fail to finish needed work if the timeout is
+short.
+
+
+User-space API
+==============
+
+Write "lockname" or "lockname timeout" to /sys/power/wake_lock lock and if
+needed create a wakelock. The timeout here is specified nanoseconds.
+Write "lockname" to /sys/power/wake_unlock to unlock a user wakelock.
+
+Do not use randomly generated wakelock names as there is no api to free
+a user-space wakelock.
+
diff --git a/include/linux/wakelock.h b/include/linux/wakelock.h
new file mode 100755
index 0000000..b17e993
--- /dev/null
+++ b/include/linux/wakelock.h
@@ -0,0 +1,92 @@
+/* include/linux/wakelock.h
+ *
+ * Copyright (C) 2007-2008 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_WAKELOCK_H
+#define _LINUX_WAKELOCK_H
+
+#include <linux/list.h>
+#include <linux/ktime.h>
+
+/* A wake_lock prevents the system from entering suspend or other low power
+ * states when active. If the type is set to WAKE_LOCK_SUSPEND, the wake_lock
+ * prevents a full system suspend. If the type is WAKE_LOCK_IDLE, low power
+ * states that cause large interrupt latencies or that disable a set of
+ * interrupts will not entered from idle until the wake_locks are released.
+ */
+
+enum {
+	WAKE_LOCK_SUSPEND, /* Prevent suspend */
+	WAKE_LOCK_IDLE,    /* Prevent low power idle */
+	WAKE_LOCK_TYPE_COUNT
+};
+
+struct wake_lock {
+#ifdef CONFIG_HAS_WAKELOCK
+	struct list_head    link;
+	int                 flags;
+	const char         *name;
+	unsigned long       expires;
+#ifdef CONFIG_WAKELOCK_STAT
+	struct {
+		int             count;
+		int             expire_count;
+		int             wakeup_count;
+		ktime_t         total_time;
+		ktime_t         prevent_suspend_time;
+		ktime_t         max_time;
+		ktime_t         last_time;
+	} stat;
+#endif
+#endif
+};
+
+#ifdef CONFIG_HAS_WAKELOCK
+
+void wake_lock_init(struct wake_lock *lock, int type, const char *name);
+void wake_lock_destroy(struct wake_lock *lock);
+void wake_lock(struct wake_lock *lock);
+void wake_lock_timeout(struct wake_lock *lock, long timeout);
+void wake_unlock(struct wake_lock *lock);
+
+/* wake_lock_active returns a non-zero value if the wake_lock is currently
+ * locked. If the wake_lock has a timeout, it does not check the timeout,
+ * but if the timeout had already expired when it was checked elsewhere
+ * this function will return 0.
+ */
+int wake_lock_active(struct wake_lock *lock);
+
+/* has_wake_lock returns 0 if no wake locks of the specified type are active,
+ * and non-zero if one or more wake locks are held. Specifically it returns
+ * -1 if one or more wake locks with no timeout are active or the
+ * number of jiffies until all active wake locks time out.
+ */
+long has_wake_lock(int type);
+
+#else
+
+static inline void wake_lock_init(struct wake_lock *lock, int type,
+					const char *name) {}
+static inline void wake_lock_destroy(struct wake_lock *lock) {}
+static inline void wake_lock(struct wake_lock *lock) {}
+static inline void wake_lock_timeout(struct wake_lock *lock, long timeout) {}
+static inline void wake_unlock(struct wake_lock *lock) {}
+
+static inline int wake_lock_active(struct wake_lock *lock) { return 0; }
+static inline long has_wake_lock(int type) { return 0; }
+
+#endif
+
+#endif
+
-- 
1.6.1

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