Re: [PATCH] USB: disable autosuspend by default for non-hubs

On Mon, 20 Aug 2007, Oliver Neukum wrote:

> Am Montag 20 August 2007 schrieb Alan Stern:
> > This patch (as965) disables autosuspend by default for all USB devices
> > other than hubs.  We are seeing too many devices that can't suspend or
> > resume properly, the blacklist is growing unreasonably quickly, and
> > this sort of thing should be handled in userspace.
> 
> This is unreasonably broad. The drivers may dictate that a device cannot
> autosuspend by not setting the flag. Why do you want to override their
> decision if they do set the flag?

Three reasons:

     1. It takes time to load driver modules, especially during bootup
	when lots of things are happening.  During that time a device
	can be autosuspended by mistake, even though the driver (had
	it been present) would not have allowed it.

     2. Drivers don't know about all possible bad devices.  By erring
	on the side of safety we can prevent (for example) storage 
	devices that work in 2.6.22 from breaking in 2.6.23.

     3. It isn't a complete override of the driver's decision, since
	the user can still enable autosuspend.  In fact there should be
	a user program that checks each USB device, as it is detected,
	against a database to see whether it should be allowed to
	autosuspend and what the idle delay should be.

Alan Stern


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