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PM: update docs for writing .../power/state

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Updates to match current code:

 - Make writes to the /sys/devices/.../power/state files fail cleanly
   if the device requires the irqs-off call variants.

 - Fix comments describing the /sys/devices/.../power/state file writes
   to match the code; the last several releases have invalidated the
   previous text.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
David Brownell 2006-08-30 14:12:48 -07:00 committed by Greg Kroah-Hartman
parent 4fc0840006
commit 047bda3615
1 changed files with 19 additions and 10 deletions
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29
drivers/base/power/sysfs.c
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@ -11,18 +11,23 @@
* state - Control current power state of device
*
* show() returns the current power state of the device. '0' indicates
* the device is on. Other values (1-3) indicate the device is in a low
* the device is on. Other values (2) indicate the device is in some low
* power state.
*
* store() sets the current power state, which is an integer value
* between 0-3. If the device is on ('0'), and the value written is
* greater than 0, then the device is placed directly into the low-power
* state (via its driver's ->suspend() method).
* If the device is currently in a low-power state, and the value is 0,
* the device is powered back on (via the ->resume() method).
* If the device is in a low-power state, and a different low-power state
* is requested, the device is first resumed, then suspended into the new
* low-power state.
* store() sets the current power state, which is an integer valued
* 0, 2, or 3. Devices with bus.suspend_late(), or bus.resume_early()
* methods fail this operation; those methods couldn't be called.
* Otherwise,
*
* - If the recorded dev->power.power_state.event matches the
* target value, nothing is done.
* - If the recorded event code is nonzero, the device is reactivated
* by calling bus.resume() and/or class.resume().
* - If the target value is nonzero, the device is suspended by
* calling class.suspend() and/or bus.suspend() with event code
* PM_EVENT_SUSPEND.
*
* This mechanism is DEPRECATED and should only be used for testing.
*/
static ssize_t state_show(struct device * dev, struct device_attribute *attr, char * buf)
@ -38,6 +43,10 @@ static ssize_t state_store(struct device * dev, struct device_attribute *attr, c
pm_message_t state;
int error = -EINVAL;
/* disallow incomplete suspend sequences */
if (dev->bus && (dev->bus->suspend_late || dev->bus->resume_early))
return error;
state.event = PM_EVENT_SUSPEND;
/* Older apps expected to write "3" here - confused with PCI D3 */
if ((n == 1) && !strcmp(buf, "3"))