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From: Doug Rabson <dfr@nlsystems.com>
To: Poul-Henning Kamp <phk@phk.freebsd.dk>
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Subject: Re: kldunload DIAGNOSTIC idea...
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On Wed, 2004-07-21 at 10:21, Poul-Henning Kamp wrote:
> In message <200407211010.08159.dfr@nlsystems.com>, Doug Rabson writes:
> 
> >The original intention was that drivers use the 
> >device_busy()/device_unbusy() counter to handle these things. In some 
> >cases, just calling device_busy() from fooopen() and device_unbusy() 
> >from fooclose() is sufficient.
> 
> That is not enough.  All methods in cdevsw, and things not in cdevsw
> (clone handlers, call backs, etc etc) needs to refcount.
> 
> I have a lot of this working in a tree here, and will commit it once
> I have gone over it a few more times.

Methods in cdevsw which can't be called unless the device is opened can
rely on a single counter managed by open/close in most cases. Other
callbacks may or may not need extra handling depending on whether or not
the callback can persist past close.

Will you use the existing device_busy() counter or will each driver use
its own counter?