Re: [RFC] Delay EHCI initialization until khubd is idle

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Tue, 2 Sep 2008, Greg KH wrote:

> On Tue, Sep 02, 2008 at 11:32:50AM -0400, Alan Stern wrote:
> > Everybody:
> > 
> > Frans Pop has been bothered by the error messages that appear in the 
> > system log when EHCI initialization interrupts the initialization of 
> > devices attached to the companion controllers.
> > 
> > The patch below provides a way to prevent these messages from being
> > generated, most of the time.  It forces EHCI initialization to wait
> > until khubd is idle, which won't happen until all devices attached to a
> > companion controller have been initialized and enumerated, though not
> > necessarily probed.
> > 
> > Now this is cosmetic at best.  Devices will still suffer a short
> > disconnection when EHCI starts up; the difference is that now the
> > errors will affect the drivers bound to those devices rather than
> > affecting khubd.  Since drivers tend to produce relatively few error
> > messages when a disconnect occurs (unlike khubd which tends to complain
> > a lot), the log remains cleaner.
> > 
> > In theory this might even be detrimental.  For example, it's possible
> > that the delay might allow time for a USB flash drive to be mounted
> > before it is disconnected, instead of being disconnected before
> > usb-storage can bind to it.
> 
> Yeah, I would worry about this thing happening a lot, that's not good,
> and can slow down the boot process even more.
> 
> If the messages are annoying people, can we just change them to
> debugging levels instead?

I suppose so.  But what happens if someone plugs in a device and it 
really does fail to initialize or enumerate?  Shouldn't that cause an 
error message to appear?

Alan Stern

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