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