Staging: only build the tree if we really want to

[linux-2.6-omap-h63xx.git] / Documentation / power / devices.txt

diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index c53d263619194f7e04719e0a7250944b0134d598..421e7d00ffd03a81fa1573656b39d489b045cd23 100644 (file)
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -196,6 +196,11 @@ its parent; and can't be removed or suspended after that parent.
 
 The policy is that the device tree should match hardware bus topology.
 (Or at least the control bus, for devices which use multiple busses.)
+In particular, this means that a device registration may fail if the parent of
+the device is suspending (ie. has been chosen by the PM core as the next
+device to suspend) or has already suspended, as well as after all of the other
+devices have been suspended.  Device drivers must be prepared to cope with such
+situations.
 
 
 Suspending Devices
@@ -310,9 +315,12 @@ used with suspend-to-disk:
     PM_EVENT_SUSPEND -- quiesce the driver and put hardware into a low-power
        state.  When used with system sleep states like "suspend-to-RAM" or
        "standby", the upcoming resume() call will often be able to rely on
-       state kept in hardware, or issue system wakeup events.  When used
-       instead with suspend-to-disk, few devices support this capability;
-       most are completely powered off.
+       state kept in hardware, or issue system wakeup events.
+
+    PM_EVENT_HIBERNATE -- Put hardware into a low-power state and enable wakeup
+       events as appropriate.  It is only used with hibernation
+       (suspend-to-disk) and few devices are able to wake up the system from
+       this state; most are completely powered off.
 
     PM_EVENT_FREEZE -- quiesce the driver, but don't necessarily change into
        any low power mode.  A system snapshot is about to be taken, often
@@ -329,8 +337,8 @@ used with suspend-to-disk:
        wakeup events nor DMA are allowed.
 
 To enter "standby" (ACPI S1) or "Suspend to RAM" (STR, ACPI S3) states, or
-the similarly named APM states, only PM_EVENT_SUSPEND is used; for "Suspend
-to Disk" (STD, hibernate, ACPI S4), all of those event codes are used.
+the similarly named APM states, only PM_EVENT_SUSPEND is used; the other event
+codes are used for hibernation ("Suspend to Disk", STD, ACPI S4).
 
 There's also PM_EVENT_ON, a value which never appears as a suspend event
 but is sometimes used to record the "not suspended" device state.