From owner-freebsd-current@FreeBSD.ORG Mon Sep 8 13:41:56 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 530561065670 for ; Mon, 8 Sep 2008 13:41:56 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.freebsd.org (Postfix) with ESMTP id DEA138FC16 for ; Mon, 8 Sep 2008 13:41:55 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 1E6A046C7C; Mon, 8 Sep 2008 09:41:52 -0400 (EDT) Date: Mon, 8 Sep 2008 14:41:53 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: vehemens In-Reply-To: <200809080350.41579.vehemens@verizon.net> Message-ID: References: <200809080202.00664.vehemens@verizon.net> <20080908100415.GI2038@deviant.kiev.zoral.com.ua> <200809080350.41579.vehemens@verizon.net> User-Agent: Alpine 1.10 (BSF 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed 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 13:41:56 -0000 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? Robert N M Watson Computer Laboratory University of Cambridge