Re: Disable autosuspend for scanners/printers

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.

I'm beginning to agree with Matthew Garrett that autosuspend should be 
disabled by default except for known-good devices and device classes...

> > 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.

> > 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.

Alan Stern


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