linux-kernel - Re: [PATCH 02/10] xhci: 'noxhci_port

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Date:	Wed, 21 May 2014 15:31:38 +0900
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Takashi Iwai <tiwai@...e.de>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	USB list <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Holger Hans Peter Freyther <holger@...ji-mobile.com>,
	Oliver Neukum <oneukum@...e.de>
Subject: Re: [PATCH 02/10] xhci: 'noxhci_port_switch' kernel parameter

On Tue, May 20, 2014 at 11:21:03PM -0700, Dan Williams wrote:
> On Tue, May 20, 2014 at 5:27 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> >> Greg,
> >>
> >> Sorry, I don't think it is fair to users to force them to re-compile
> >> their kernel to get their device to work.
> >
> > I totally agree.
> >
> >> Granted, I'm new to USB
> >> development, but the rate of reports of endpoint devices that mess up
> >> and require quirks in the hcd-driver or usb-core seems un-ending to
> >> me.  So, I don't think it is fair to expect that the tide of quirky
> >> devices will be stemmed in any reasonable amount of time.  Having a
> >> "works with noxhci_port_switch" report from users is good data (hmm, I
> >> think a printk to tell users to file a report upstream if the option
> >> resolves their issue is needed).
> >
> > How about just adding a debugfs file instead?  That way, once you fix
> > this, we can then remove it and no one will care.
> 
> The only thing stopping me from saying "deal." is that this darn
> things is presently a pci quirk.  So it happens well before the user
> has a chance to manually override it with a debugfs file.

Then have the debugfs file disconnect the device and reconnect it.

> Let me look into delaying the quirk until the driver loads, because
> ideally the right interface for this is "blacklist xhci_hcd" in
> /etc/modprobe.conf.

Which really doesn't work for systems / distros that build the driver
into the kernel.

thanks,

greg k-h
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