From owner-freebsd-hackers@FreeBSD.ORG  Wed Apr 27 15:22:46 2011
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Date: Wed, 27 Apr 2011 15:22:43 +0200
From: Bartosz Fabianowski <freebsd@chillt.de>
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Cc: Kostik Belousov <kostikbel@gmail.com>, freebsd-hackers@freebsd.org,
	Hans Petter Selasky <hselasky@c2i.net>
Subject: Re: Is there some implicit locking of device methods?
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> Err, if you use cdevpriv you shouldn't even have a d_close method.  All your
> d_close logic should be in the cdevpriv destructor

I see. There is no documentation for any of this, so I just implemented 
it in the way I *thought* it should work:

.d_close = drv_close,

int drv_close(...) {
   devfs_clear_cdevpriv();
}

static void cdevpriv_dtr(void *data) {
   free(data, M_USBDEV);
}

If I understand you correctly, I can leave out the drv_close() method. 
When close() is called, devfs_clear_cdevpriv() will be executed 
implcitly for me and my dstructor will run - right?

- Bartosz