On 09/13/2012 04:14 PM, James Bottomley wrote:

On Thu, 2012-09-13 at 15:40 +0800, Aaron Lu wrote:

quoted

The ready_to_power_off flag is used to give indication to ATA layer
if this device's power can be removed when runtime suspended.

This flag is determined by individual SCSI driver like sr, sd.

This flag is introduced to support zero power ODD. When ODD
is runtime suspended, it may not be OK to remove its power.

But for disk, it is always OK to be powered off, so set this flag.

It is? I may have missed this, but where do you flush the cache of write
back cache devices you're about to power off?

I suppose that is handled in sd_suspend callback, the power off happens
after a device is runtime suspended.

Thanks,
Aaron