On Tue, 21 Feb 2012, Lin Ming wrote:

quoted

Then maybe you can use pm_runtime_no_callbacks() for the ZPODD device.
It's explained in Documentation/power/runtime_pm.txt, and I use it for
USB interfaces.

If pm_runtime_no_callbacks() is used, runtime PM sysfs attributes
won't be created.
Then how to disable ZPODD feature in userspace?

Currently, I use "control" file of scsi device to enable/disable
ZPODD, for example
echo auto > /sys/devices/pci0000:00/0000:00:1f.2/ata0/host1/target1:0:0/1:0:0:0/power/control
echo on > /sys/devices/pci0000:00/0000:00:1f.2/ata0/host1/target1:0:0/1:0:0:0/power/control

You could get the same result by using the "control" file for the ATA
port.

quoted

The idea is that the ZPODD will never receive any runtime PM callbacks
from the PM core. �Instead the ATA port callback routines will be
responsible for power management of the ZPODD device.

Does the ATA port callback also responsible to resume its child?

For example,
/sys/devices/pci0000:00/0000:00:1f.2/ata0/host1/target1:0:0/1:0:0:0/

ata0 is resumed.

Then who will be responsible to resume host1, target1:0:0 and 1:0:0:0?

Or do you mean that we don't need to resume these devices at all?
host1 and target1:0:0 are logical devices, but I think 1:0:0:0 is not.

That's right.  It makes no difference whether the host and target 
are resumed or suspended.  In fact, you could also call 
pm_runtime_no_callbacks() for them.

Alan Stern