Am Sonntag 12 August 2007 schrieb Alan Stern:
> On Sun, 12 Aug 2007, Oliver Neukum wrote:
>
> > Am Donnerstag 09 August 2007 schrieb Alan Stern:
> > > Oliver and Pete:
> > >
> > > Is it possible to replace all those USB_QUIRK_NO_AUTOSUSPEND entries
> > > for scanners with a single class-wide entry?
> >
> > Which class? It would have to blanket all vendor specific devices.
> > This is a rather broad swipe.
>
> I was hoping there would be a specific device class for scanners. Oh
> well.
It is a flaw in the USB spec.
> I'm beginning to agree with Matthew Garrett that autosuspend should be
> disabled by default except for known-good devices and device classes...
We could simply revert to enabling autosuspend only for those devices
whose driver requests it. Most problems are with devices accessed through
usbfs.
> > > What about printers?
> >
> > Just remove the autosuspend support from the driver if you really
> > want to do this.
>
> Is that good enough? If a printer is plugged in when the system boots,
> the delay between enumerating the device and loading the driver can be
> long enough for the device to get autosuspended.
How many devices truely crash?
> > > Would a USB_QUIRK_RESET_RESUME entry suffice or do we really need
> > > NO_AUTOSUSPEND?
> >
> > Having no way to test, I am conservative. Besides, is RESET_RESUME
> > the right thing to do for a device driven by usbfs? It would turn close()
> > into an operation that can cause a reset as a side effect.
>
> There's nothing wrong with that. The kernel makes no guarantees about
> what happens to a device driven by usbfs while its file is closed.
> The next program to open the file can't depend on finding the device in
> any particular state; this has always been true.
In theory you are right. In theory there's no difference to practice.
Before autsuspend the kernel left devices alone unless user space
requested action.
Regards
Oliver
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