From owner-freebsd-current@FreeBSD.ORG Mon Sep 8 16:45:50 2008 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 63DFF106564A; Mon, 8 Sep 2008 16:45:50 +0000 (UTC) (envelope-from vehemens@verizon.net) Received: from vms042pub.verizon.net (vms042pub.verizon.net [206.46.252.42]) by mx1.freebsd.org (Postfix) with ESMTP id 47F948FC13; Mon, 8 Sep 2008 16:45:50 +0000 (UTC) (envelope-from vehemens@verizon.net) Received: from sam ([71.106.250.178]) by vms042.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0K6V003ICYJSO45A@vms042.mailsrvcs.net>; Mon, 08 Sep 2008 11:45:29 -0500 (CDT) Date: Mon, 08 Sep 2008 09:50:55 -0700 From: vehemens In-reply-to: To: Robert Watson Message-id: <200809080950.55528.vehemens@verizon.net> MIME-version: 1.0 Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: 7bit Content-disposition: inline References: <200809080202.00664.vehemens@verizon.net> <200809080350.41579.vehemens@verizon.net> User-Agent: KMail/1.9.10 Cc: Kostik Belousov , freebsd-current@freebsd.org Subject: Re: bsd versus linux device drivers X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Sep 2008 16:45:50 -0000 On Monday 08 September 2008 06:41:53 am Robert Watson wrote: > On Mon, 8 Sep 2008, vehemens wrote: > > On Monday 08 September 2008 03:04:15 am Kostik Belousov wrote: > >> On Mon, Sep 08, 2008 at 02:02:00AM -0700, vehemens wrote: > >>> In linux drivers, there is a one to one relationship to an open and a > >>> calling argument structure called struct file. It provides a private > >>> data pointer that allows the driver to preserve unique state > >>> information across other calls such as read/write/ioctl/mmap/close etc. > >>> > >>> For bsd drivers, my understanding there is not an equivalent. As a > >>> result it is not possible to preserve different state information for > >>> multiple opens by the same thread of the same device major/minor #'s. > >>> > >>> Is this correct, or did i miss something? > >> > >> There is devfs_{get,set}_cdevpriv() KPI. Still no manpage, I shall fix > >> this ASAP. > > > > Just started looking at the firewire driver which has clone. It looks > > like it hooks into the event handler. > > > > Don't quite understand it all yet, so I'm going to look forward to that > > man page. > > Many device drivers continue to use the old clone interface, but are > gradually being converted over. You can look at the definitions and list > of converted drivers here: > > http://fxr.watson.org/fxr/ident?im=bigexcerpts;i=devfs_set_cdevpriv > > Looking at some of the converted drivers, I find myself a bit worried by > the extra error handling: in what situations do we expect that bpfioctl() > might be called without its cdev-private data? Got it now. Looks like the converted drivers are only in current, but the KPI is in at least 7.x as well.