On Wed, 2012-09-19 at 13:27 +0100, James Bottomley wrote:

quoted

I think we could do this with a couple of flags sitting inside struct
device itself: one for pm state and capabilities defined at a generic
level and one for device specific pm state.  The latter would be for
things like the door lock information which is very specific to CDs
(although not specific to SCSI CDs).  Alternatively, even if we can't
use these capabilities at the generic pm level, we still need an
internal state set of flags because power state stuff traverses the
stack and struct device is the only universal object in that stack.

FWIW the SATA Device Sleep support, which is currently only used (in a
patch which is pending) automatically as an extension of the AHCI link
power management, can also be triggered manually by a GPIO line; I've
got a platform where it's done with an ACPI call. I suspect we'll see
that kind of manual setup on a few embedded platforms too.

If we're working on hooking this up through the device layers, perhaps
that's worth taking into consideration?

--

Hi David,

For SATA Device sleep, what's the appropriate time to set the Device sleep,
this seems also part of runtime PM?

Best regards!

Jack