linux-kernel - Re: [linux-usb-devel] 2.6.20-rc4: usb somehow broken

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Date:	Sun, 14 Jan 2007 14:23:50 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Prakash Punnoor <prakash@...noor.de>
cc:	Oliver Neukum <oliver@...kum.org>, <linux-kernel@...r.kernel.org>,
	<linux-usb-devel@...ts.sourceforge.net>
Subject: Re: [linux-usb-devel] 2.6.20-rc4: usb somehow broken

On Sun, 14 Jan 2007, Prakash Punnoor wrote:

> Am Sonntag 14 Januar 2007 10:28 schrieb Oliver Neukum:
> > Am Sonntag, 14. Januar 2007 10:08 schrieb Prakash Punnoor:
> > > Am Donnerstag 11 Januar 2007 18:28 schrieb Oliver Neukum:
> > > > Am Donnerstag, 11. Januar 2007 18:20 schrieb Prakash Punnoor:
> > > > > Hi,
> > > > >
> > > > > I can't scan anymore. :-( I don't know which rc kernel introduced it,
> > > > > but this are the messages I get (w/o touching the device/usb cable
> > > > > except pluggin it in for the first time):
> > > > >
> > > > > usb 1-1.2: new full speed USB device using ehci_hcd and address 4
> > > > > ehci_hcd 0000:00:0b.1: qh ffff81007bc6c280 (#00) state 4
> > > > > usb 1-1.2: configuration #1 chosen from 1 choice
> > > > > usb 1-1.2: USB disconnect, address 4
> > > > > usb 1-1.2: new full speed USB device using ehci_hcd and address 5
> > > > > usb 1-1.2: configuration #1 chosen from 1 choice
> > > > > usb 1-1.2: USB disconnect, address 5
> > > > > usb 1-1.2: new full speed USB device using ehci_hcd and address 6
> > > > > usb 1-1.2: configuration #1 chosen from 1 choice
> > > > > usb 1-1.2: USB disconnect, address 6
> > > > > usb 1-1.2: new full speed USB device using ehci_hcd and address 7
> > > > > usb 1-1.2: configuration #1 chosen from 1 choice
> > > > > usb 1-1.2: USB disconnect, address 7
> > > > > usb 1-1.2: new full speed USB device using ehci_hcd and address 8
> > > > > usb 1-1.2: configuration #1 chosen from 1 choice
> >
> > [..]
> >
> > > Hi, I did more tests and I was wrong about "broken". It seems more a
> > > time-out problem, ie if I try to use sane again in short intervalls, I
> > > will get my device working. The cause seems CONFIG_USB_SUSPEND=y. With
> > > 2.6.20-rc5 the
> >
> > Have you confirmed that by using a kernel without  CONFIG_USB_SUSPEND ?
> 
> Yes. I compiled the modules with various settings, reloaded the modules and 
> above option made the difference. I also don't get the disconnect mesages, as 
> well, w/o USB_SUSPEND.

Judging from the log, it looks like the scanner cannot handle being
suspended.  (BTW this is in violation of the USB specification -- all
devices must be able to suspend and resume.)

When the scanner is not in use, the system automatically suspends it after 
two seconds.  When you use sane the scanner is resumed, but it then 
disconnects itself and reconnects.  Sane is left trying to control the
disconnected device instance, so of course it fails.

I'm beginning to think that we need some way to deal with devices that 
cannot recover from a suspend.  Several examples have cropped up.  
Unfortunately, I can't think of anything better than a blacklist, which is 
not very satisfactory.

Can anyone suggest another approach?

Alan Stern

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