Date: Wed, 27 Aug 2008 15:16:18 -0400 (EDT)
From: Alan Stern <stern@rowland.harvard.edu>
To: Oliver Neukum <oliver@neukum.org>
cc: Greg KH <greg@kroah.com>, USB list <linux-usb@vger.kernel.org>,
       Stefan Kopp <stefan_kopp@agilent.com>, Marcel Janssen <korgull@home.nl>,
       Felipe Balbi <me@felipebalbi.com>,
       Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] USB: add USB test and measurement class driver - round
 2
In-Reply-To: <200808272105.50169.oliver@neukum.org>
Message-ID: <Pine.LNX.4.44L0.0808271513270.2138-100000@iolanthe.rowland.org>
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On Wed, 27 Aug 2008, Oliver Neukum wrote:

> Am Mittwoch 27 August 2008 20:58:08 schrieb Alan Stern:
> > > And this rule depends on sharing the USB major or not. This needs
> > > a big fat mention in Documentation.
> > 
> > You mean that the open/disconnect locking rule applies only to drivers 
> > that call usb_register_dev, i.e, drivers using the USB major. ?Right?
> 
> Yes. In fact drivers not using the USB major but their own char devices
> will need such a lock. This is tricky.

IMO all char-device registration/deregistration routines should use a 
similar rwsem.  Then device drivers wouldn't need to worry about it.

> > I agree that it deserves to be mentioned in the documentation 
> > somewhere. ?Where would be a good place? ?None of the existing files in 
> > Documentation/usb seem appropriate.
> 
> The USB major merits a file of its own.

I don't feel competent to start writing such a file.  Greg, what do you 
think?  Maybe all that's needed to get going is to "borrow" some of the 
material in LDD3.  :-)

Alan Stern

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