SCSI midlayer power management

Hi,

This proposed patch implements enough power-management support within the SCSI midlayer to get ACPI S3 working on my system. Changes as follows:

* Add generic_scsi_{suspend,resume} methods to scsi.c
* Add suspend and resume callbacks to the scsi_driver structure, and implement those callbacks in sd.c
* In sd.c, we call sd_shutdown on suspend, in order to synchronize the write-back cache.
* In sd.c, we call sd_rescan from sd_resume in order to ensure that drives have spun up and avoid passing not ready errors back to the block layer.
* In generic_scsi_suspend, we call scsi_device_quiesce before calling the scsi_driver suspend callback. We resume from quiesce state in reverse order in generic_scsi_resume.

ACPI S1 and S4/swsusp are untested, but I think there should be no regressions with S1. To do S1 properly, we probably need to tell the drive to spin down, and I don't know what the SCSI command is for that... For S4, the call to scsi_device_quiesce might pose a problem for the subsequent state dump to disk. But I'm not sure swsusp ever worked for SCSI.

This might help SATA drives, too, but I seem to remember that the SATA layer doesn't properly emulate the SYNCHRONIZE_CACHE command.

Comments, anybody? Can this be applied upstream? I think it's a step in the right direction.

Applies to scsi-misc-2.6

Nathan

That was something Mark Lord reported higher level I suspect - which is that the scsi path is disabled before the sync cache command is sent so the command is always errored before it hits the drive

That applies to shutdown, I have no idea whether it also applies to suspend.

Thanks
Nathan

Yes, this one's my fault. I have patches to fix this, I never got around to merging them. Randy was on at me yesterday about this too. I'll dig them out. (The problem is that last sync is sent in SDEV_DEL state, so it gets rejected).

James