From owner-freebsd-hackers  Fri Oct 18 16:12:51 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id QAA29923
          for hackers-outgoing; Fri, 18 Oct 1996 16:12:51 -0700 (PDT)
Received: from seine.cs.umd.edu (10862@seine.cs.umd.edu [128.8.128.59])
          by freefall.freebsd.org (8.7.5/8.7.3) with ESMTP id QAA29918
          for <freebsd-hackers@freebsd.org>; Fri, 18 Oct 1996 16:12:48 -0700 (PDT)
Received: by seine.cs.umd.edu (8.7.6/UMIACS-0.9/04-05-88)
	id TAA04920; Fri, 18 Oct 1996 19:12:43 -0400 (EDT)
Date: Fri, 18 Oct 1996 19:12:43 -0400 (EDT)
From: rohit@cs.umd.edu (Rohit Dube)
Message-Id: <199610182312.TAA04920@seine.cs.umd.edu>
To: freebsd-hackers@freebsd.org
Subject: Conventions/Rules for adding Local ioctls
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk


Hi,

I have been writing a pseudo-device driver (using a Major Device
number reserved for local use). I need to add some ioctls to 
this pseudo-device driver.

I was wondering if there are any (FreeBSD/BSD/Unix) rules which specify
the definition of new local ioctls? In other words, how do I add a
'group' and a 'num' to an ioctl command meant for local consumption,
without running the risk of conflicting with any current or future
code? 

Thanks.

--rohit.

PS:

sys/sys/ioccom.h -
#define _IOC(inout,group,num,len) \
      (inout | ((len & IOCPARM_MASK) << 16) | ((group) << 8) | (num))
#define _IOWR(g,n,t)    _IOC(IOC_INOUT, (g), (n), sizeof(t))

sys/net/local.h
#define _IOWR ('?', ???, u_int)