Re: [PATCH] USB: add USB test and measurement class driver - round 2

Greg KH
2008-08-28T00:04:40Z

On Wed, Aug 27, 2008 at 03:16:18PM -0400, Alan Stern wrote:
> 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. :-)

Well, as the USB chapter in LDD3 "borrowed" heavily from the comments in
the usb code itself, that would only be fair :)

That chapter needs to be reworked. The authors and Oreilly and I are
currently talking about how to do this all in a framework that makes
sense (the current one of a book every few years that quickly gets out
of date doesn't make sense.)

thanks,

greg k-h