Date: Wed, 7 Nov 2007 18:29:52 +0200 From: Kostik Belousov <kostikbel@gmail.com> To: freebsd-arch@freebsd.org Subject: Re: fdclone KPI Message-ID: <20071107162951.GA37471@deviant.kiev.zoral.com.ua> In-Reply-To: <20071031150620.GT37471@deviant.kiev.zoral.com.ua> References: <20071031150620.GT37471@deviant.kiev.zoral.com.ua>
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--GUfsrdPq8omuo5Le Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 31, 2007 at 05:06:20PM +0200, Kostik Belousov wrote: > Dear arch@ readers, > with the important help from Peter Holm I have implemented the KPI that > provides the ability for the driver to implement cloning on the open(2). > This is another (IMHO, more UNIXy) way to provide per-fd private data > for the driver. It seems that at least /dev/apm, /dev/drm and /dev/sg > could immediately benefit from the fdclone() KPI. >=20 > The patch is at > http://people.freebsd.org/~kib/misc/fdclone.9.patch As Oleksandr Tymoshenko pointed out, the patch was not really available at this address. Fixed, sorry. > Sample dumb driver that uses the KPI is at > http://people.freebsd.org/~kib/fclone >=20 > The driver that uses the fdclone() shall provide cdevsw for master device, > and cdevsw for clones. Master shall have d_fdopen() method that could call > int fdclone(struct cdevsw *_csw, struct file *_fp, int _fmode, > struct cdev **_clone, void *si_drv1, struct thread *td); > to replace the reference in the _fp with newly created cdev. >=20 > After successfull fdclone() call, all further calls on the _fp > are dispatched to the clone _csw instead of master one. si_drv1 of the > new cdev is set to respective argument, allowing the clone to find the > master. >=20 > The cloned cdev is not accessible for lookup through the devfs, and is > destroyed automatically on the final close of the last filedescriptor that > references the vnode. >=20 > Please, review. Your feedback is welcome ! --GUfsrdPq8omuo5Le Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFHMef/C3+MBN1Mb4gRAn8KAJ4x3J+nj7bdvdRbwZOOjHaGnWXaQgCcDogL 5F8lAqBVDBo4JplfHq3t7PY= =SOI0 -----END PGP SIGNATURE----- --GUfsrdPq8omuo5Le--
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