Re: [PATCH] USB: add usbfs stubs for suspend, resume, etc.

[Oliver Neukum <oliver@xxxxxxxxxx>]

Am Montag, 3. Dezember 2007 23:09:07 schrieb Alan Stern:
> On Mon, 3 Dec 2007, Oliver Neukum wrote:
> > Am Montag, 3. Dezember 2007 21:43:11 schrieb Alan Stern:
> > > THis patch (as1022) adds stub methods for suspend/resume/reset_resume
> > > and pre-rreset/post-reset to the usbfs_driver.  There isn't much they
> > > can do, since there's no way to inform a user task about any of these
> >
> > In this case, shouldn't resume/reset_resume/post_reset report
> > errors?
>
> Well, no.  That would be just as bad as not having the stubs in the
> first place.

Yes, you are running up against a limitation in the system.

> Not only is it impossible to tell user-level drivers about suspend,
> etc. events, it's also not possible to tell them that they have been

-ENODEV. Last time I looked usbfs had a disconnect() method.

> unbound!  So I wanted to be conservative and keep the kernel's current
> behavior: The suspend/resume/reset happens and the user-level driver is
> blissfully igorant of it.

In theory, blissfully ignoring suspend/resume must work. Anything
that involves a reset cannot. User space must be prepared with
a surprise unplug. Surprise state change asks too much.

	Regards
		Oliver



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