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

Alan Stern
2008-08-27T18:58:20Z

On Wed, 27 Aug 2008, Greg KH wrote:

> On Wed, Aug 27, 2008 at 02:28:22PM -0400, Alan Stern wrote:
> > On Wed, 27 Aug 2008, Greg KH wrote:
> >
> > > Here's an updated version of the usbtmc driver, with all of the
> > > different issues that have been raised, hopefully addressed.
> >
> > This is an example of what I was discussing with Oliver. In all
> > likelihood you simply don't need usbtmc_mutex, and using it will cause
> > a lockdep violation.
> >
> > That's why so many of the other USB class drivers don't have an
> > analogous static mutex.
>
> Ok, then it's just safe to drop this static mutex entirely, right?

Yes, once you add the call to usb_deregister_dev.

On Wed, 27 Aug 2008, Oliver Neukum wrote:

> 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?

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.

Alan Stern