PM: update docs for writing .../power/state
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>
diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 40d7242..e55b3c2 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -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 @@
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"))