Am Mittwoch, 30. Juni 2004 16:58 schrieben Sie:
> On Wed, 30 Jun 2004, Oliver Neukum wrote:
>
> > Am Mittwoch, 30. Juni 2004 01:57 schrieb David Brownell:
> > > Alan Stern wrote:
> > >
> > > > Come to think of it, there really is almost no difference between an
> > > > unsolicited device reset and a power-off suspend (except that one is
> > > > quicker than the other). No difference at all as far as anything in the
> > > > USB stack is concerned, it seems to me.
> > >
> > > Actually there is a difference. One retains VBUS power, and the
> > > other one doesn't -- it's pretty significant, actually.
> > >
> > > For example, a bus-powered device would lose its firmware updates
> > > when VBUS is lost, and need much more re-initialization (commonly
> > > a couple more enumerations in addition to one or more firmware
> > > updates) before it can even get to the same "device reset" stage.
>
> Ooh, yes, I had forgotten about that.
>
> > That is not a fundamental difference. The reset logic also has a device
> > morphed code path.
>
> But it does mean that it's effectively impossible to do a power-off
> resume on such a device. When the power gets restored the device will
> have "morphed" and so the hub driver will call usb_disconnect(). Perhaps
> you believe this is acceptable; I have no opinion one way or the other.
Better than nothing. But is there a reason the determination of "morphed"
state must be made before resume() ?
> USB recognizes three different power states: power-on, suspended, and
> power-off. The question is: Should it be possible to use the power-off
> state as a surrogate for an extremely low-power suspend state (like
> suspend-to-disk)? Unfortunately the current API doesn't allow for such
> distinctions; the suspend() method in usb_driver doesn't include an
> argument to indicate which sort of suspend is about to occur. Oddly
Probably an error. I see no good reason to drop the argument during
the call chain.
Regards
Oliver
-------------------------------------------------------
This SF.Net email sponsored by Black Hat Briefings & Training.
Attend Black Hat Briefings & Training, Las Vegas July 24-29 -
digital self defense, top technical experts, no vendor pitches,
unmatched networking opportunities. Visit www.blackhat.com
_______________________________________________
[EMAIL PROTECTED]
To unsubscribe, use the last form field at:
https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
