From owner-freebsd-drivers@FreeBSD.ORG  Tue May 18 08:49:35 2010
Return-Path: <owner-freebsd-drivers@FreeBSD.ORG>
Delivered-To: freebsd-drivers@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id A8F36106564A
	for <freebsd-drivers@freebsd.org>; Tue, 18 May 2010 08:49:35 +0000 (UTC)
	(envelope-from indranil@virident.com)
Received: from caexchgw.virident.com (caexchgw.virident.com [209.31.25.116])
	by mx1.freebsd.org (Postfix) with ESMTP id 865508FC1A
	for <freebsd-drivers@freebsd.org>; Tue, 18 May 2010 08:49:35 +0000 (UTC)
Received: from caexch1.virident.info ([172.16.32.15]) by caexchgw.virident.com
	with Microsoft SMTPSVC(6.0.3790.1830); 
	Tue, 18 May 2010 01:49:29 -0700
X-MimeOLE: Produced By Microsoft Exchange V6.5
Content-class: urn:content-classes:message
MIME-Version: 1.0
Date: Tue, 18 May 2010 01:49:26 -0700
Message-ID: <28631E6913C8074E95A698E8AC93D09101B5C093@caexch1.virident.info>
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
Thread-Topic: Storage driver design question
Thread-Index: Acr2ZwVszeFegUKXQJi2HRY2mOrGpA==
From: "Indranil Bhattacharya" <indranil@virident.com>
To: <freebsd-drivers@freebsd.org>
X-OriginalArrivalTime: 18 May 2010 08:49:29.0870 (UTC)
	FILETIME=[075732E0:01CAF667]
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
X-Content-Filtered-By: Mailman/MimeDel 2.1.5
Subject: Storage driver design question
X-BeenThere: freebsd-drivers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Writing device drivers for FreeBSD <freebsd-drivers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-drivers>, 
	<mailto:freebsd-drivers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-drivers>
List-Post: <mailto:freebsd-drivers@freebsd.org>
List-Help: <mailto:freebsd-drivers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-drivers>,
	<mailto:freebsd-drivers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 18 May 2010 08:49:35 -0000

Hi,

=20

I am writing the driver for a storage device on the latest freebsd
kernel. The device will sit on the PCIe bus.=20

As a starting point; I have written a very simple memory-disk driver
that implements a geom-class. It implements the init() method by writing
& reading from memory (that it has earlier allocated) as part of
BIO_WRITE & BIO_READ respectively. I am able to create a filesystem on
this driver & read/write files on this filesystem.

I am also writing a PCI driver for the actual hardware device. Once that
is done, I will modify the memory-disk driver to talk to this PCI driver
instead of just operating from memory.

Does this look like a correct design ?  Or should the entry point to my
driver sit somewhere else in the I/O stack ?

=20

Thanks in advance,

Indranil=20

=20

=20