Date: Sat, 04 Feb 1995 18:29:59 +0000 From: Ed Hudson <elh@p5.spnet.com> To: freebsd-hackers@FreeBSD.org Cc: elh@spnet.com Subject: controllable-predictable slip interface units Message-ID: <199502041829.SAA00370@p5.spnet.com>
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howdy.
old issue:
management of multiple slip interfaces is simpler if the
slip unit number returned by slattach is controllable
i'd like to ask you folks to consider adding the following
patch to the kernel slip interface, which makes the interface
unit assigned by slattach controllable (well, predictable) under
most circumstances.
the patch takes the last four bits of the minor device number,
and, if it is within the range of the slip interface indices,
and that slip interface is available, it is returned as the
slip unit. if none of these conditions are met, the behaviour
defaults to the current one: return the first available
slip interface unit. ie,
sl# = ((minor&0xf)<NSL && slip_free(minor&0xf)) ?
(minor&0xf) :
first_slip_free
with this, patch, slattach applied to /dev/cuaa0 uses slip
interface sl0, slattach applied to /dev/cuaa1 uses sl1, and
so on.
yes, this is an imperfect solution to this problem
in that it places requirements on minor device numbers, and
fails (softly, with the old behaviour) in the face of more
than min(NSL,16) slip interfaces, etc, but i think that it is easier
to use than the current scheme(s) typically employed.
thanks for considering adding this patch.
-elh
elh@spnet.com
based on 950202-SNAP, /usr/src/sys/net/if_sl.c
*** Orig/if_sl.c Sun Nov 27 15:29:57 1994
--- if_sl.c Sat Feb 4 18:15:45 1995
***************
*** 264,274 ****
if (tp->t_line == SLIPDISC)
return (0);
!
for (nsl = NSL, sc = sl_softc; --nsl >= 0; sc++)
if (sc->sc_ttyp == NULL) {
if (slinit(sc) == 0)
return (ENOBUFS);
tp->t_sc = (caddr_t)sc;
sc->sc_ttyp = tp;
sc->sc_if.if_baudrate = tp->t_ospeed;
--- 264,307 ----
if (tp->t_line == SLIPDISC)
return (0);
!
! #ifdef PREDICTABLE_SL
! {
! /*
! * elh 9.19.1994
! * make the interface number returned by slattach
! * predictable - make it equal to the last four bits
! * of the minor tty/cua number, if the last four bits are
! * less than NSL
! *
! * thus cuaa0 -> sl0
! * ttyd1 -> sl1
! * cuaa2 -> sl2 (if NSL >= 3)
! * cuaa45 -> old algorithm.
! *
! * if the interface is already taken (how? nunits > NSL,
! * or multiports?) then
! * the behaviour defaults to the old: it looks for
! * the lowest available sl interface
! */
! unsigned int sl_num;
! sl_num= (unsigned int) dev;
! sl_num= sl_num & 0x0f;
! if (sl_num < NSL) {
! sc= &(sl_softc[sl_num]);
! if (sc->sc_ttyp == NULL) {
! if (slinit(sc) == 0) { } else goto got_sl;
! }
! }
! }
! #endif
for (nsl = NSL, sc = sl_softc; --nsl >= 0; sc++)
if (sc->sc_ttyp == NULL) {
if (slinit(sc) == 0)
return (ENOBUFS);
+ #ifdef PREDICTABLE_SL
+ got_sl:
+ #endif
tp->t_sc = (caddr_t)sc;
sc->sc_ttyp = tp;
sc->sc_if.if_baudrate = tp->t_ospeed;
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