Re: [linux-usb-devel] question on flushing buffers and spinning down disk

On Mon, 24 Sep 2007, Oliver Neukum wrote:

> Am Montag 24 September 2007 schrieb Alan Stern:
> > On Mon, 24 Sep 2007, Oliver Neukum wrote:
> > 
> > > > subsystem implements its own form of runtime PM support, then you'll be
> > > > able to use it properly.  But until then, there isn't anything much you
> > > > can do.
> > > 
> > > Well, we can't simply cut power. Buffers must be flushed and the disk
> > > spun down. The suspend() method of the storage driver will have to become
> > > complex.
> > 
> > That's right, if the device is a real disk.  If it's a flash memory
> > device then of course these issues don't arise.  Unfortunately the
> > driver isn't able to tell one from the other; the user will have to
> > do that for us.
> 
> So those devices which draw most power we don't suspend :-(
> Furthermore for many devices it will take real user intervention to
> determine what is in the enclosure. This isn't very good. I think
> we can do better.

If by "we" you mean the Linux kernel in general, then I agree.  If by
"we" you mean the USB developers, then I disagree.  Help is needed from
the SCSI people.

Alan Stern

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