提交 ffffa4b5 编写于 作者: D David Brownell 提交者: Len Brown

PM: Remove obsolete /sys/devices/.../power/state docs

The /sys/devices/.../power/state files have been gone for a while
now, but I just noticed some documentation that still refers to
them.  (Fortunately described as DEPRECATED and WILL REMOVE).

Time to remove that obsolete documentation too ...
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: NLen Brown <len.brown@intel.com>
上级 5a0a2f30
......@@ -502,52 +502,3 @@ If the CPU can have a "cpufreq" driver, there also may be opportunities
to shift to lower voltage settings and reduce the power cost of executing
a given number of instructions. (Without voltage adjustment, it's rare
for cpufreq to save much power; the cost-per-instruction must go down.)
/sys/devices/.../power/state files
==================================
For now you can also test some of this functionality using sysfs.
DEPRECATED: USE "power/state" ONLY FOR DRIVER TESTING, AND
AVOID USING dev->power.power_state IN DRIVERS.
THESE WILL BE REMOVED. IF THE "power/state" FILE GETS REPLACED,
IT WILL BECOME SOMETHING COUPLED TO THE BUS OR DRIVER.
In each device's directory, there is a 'power' directory, which contains
at least a 'state' file. The value of this field is effectively boolean,
PM_EVENT_ON or PM_EVENT_SUSPEND.
* Reading from this file displays a value corresponding to
the power.power_state.event field. All nonzero values are
displayed as "2", corresponding to a low power state; zero
is displayed as "0", corresponding to normal operation.
* Writing to this file initiates a transition using the
specified event code number; only '0', '2', and '3' are
accepted (without a newline); '2' and '3' are both
mapped to PM_EVENT_SUSPEND.
On writes, the PM core relies on that recorded event code and the device/bus
capabilities to determine whether it uses a partial suspend() or resume()
sequence to change things so that the recorded event corresponds to the
numeric parameter.
- If the bus requires the irqs-disabled suspend_late()/resume_early()
phases, writes fail because those operations are not supported here.
- If the recorded value is the expected value, nothing is done.
- If the recorded value is nonzero, the device is partially resumed,
using the bus.resume() and/or class.resume() methods.
- If the target value is nonzero, the device is partially suspended,
using the class.suspend() and/or bus.suspend() methods and the
PM_EVENT_SUSPEND message.
Drivers have no way to tell whether their suspend() and resume() calls
have come through the sysfs power/state file or as part of entering a
system sleep state, except that when accessed through sysfs the normal
parent/child sequencing rules are ignored. Drivers (such as bus, bridge,
or hub drivers) which expose child devices may need to enforce those rules
on their own.
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