Subject: Re: usb control endpoint exclusive access
To: Lennart Augustsson <lennart@augustsson.net>
From: Quentin Garnier <cube@cubidou.net>
List: tech-kern
Date: 05/17/2005 08:33:31
--aTHdXM4WpLndGb15
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
On Tue, May 17, 2005 at 08:14:42AM +0200, Lennart Augustsson wrote:
> Berndt Josef Wulf wrote:
[...]
> >3) No support to open devices for read and write access by separate=20
> >processes
>=20
> Now this one is tricky. Linux has a different semantics for close() in
> the kernel than NetBSD. Linux calls the device open() every time the
> device is opened and close() every time the device is closed.
> NetBSD calls open() on every open, but close() only on the last close.
> The NetBSD behaviour makes it very difficult to have separate read&write
> processes. :(
It is rather easy to do clonable devices on NetBSD, now. See, e.g.,
tap(4) (in src/sys/net/if_tap.c) which actually shows both access
classes.
--=20
Quentin Garnier - cube@cubidou.net - cube@NetBSD.org
"When I find the controls, I'll go where I like, I'll know where I want
to be, but maybe for now I'll stay right here on a silent sea."
KT Tunstall, Silent Sea, Eye to the Telescope, 2004.
--aTHdXM4WpLndGb15
Content-Type: application/pgp-signature
Content-Disposition: inline
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.6 (NetBSD)
iQEVAwUBQomQO9goQloHrPnoAQIGpggAucD/GvwFuPHOKfGYzTqmyFXGhyYQxg0h
gIEc8rPzS1tZQgm2Ml5vHfMTR2G2yNMKK6JjLXy0m+HsNl3XXeJAwcsRufqinbIK
SYh4P1uX/GAZAC3lGEXy4yfzmZE8gNGaz0l7HTSHlxeN06IhdjLtKDFSRaOPqtkF
aQ+w3/0p57D0X3OvNdTWt4Gninp7+/p25iF+oyhca7T7m5D0TsAF5zMF9waFvuFh
qmG375FslfrZF0hyaH184zQQG8L5YiJLG3JOk9z2apZF8lItiIp3E5KaZ5y8aUU+
Z+1pYCXBGh5tqUAfJuNF9rkBtlwj1Bt2vQgnOaGL3EAXGkz/2N7Atw==
=8EzS
-----END PGP SIGNATURE-----
--aTHdXM4WpLndGb15--