From owner-freebsd-hackers@FreeBSD.ORG  Fri Jul 24 10:42:38 2009
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 36AA51065673;
	Fri, 24 Jul 2009 10:42:38 +0000 (UTC)
	(envelope-from a_best01@uni-muenster.de)
Received: from zivm-out3.uni-muenster.de (ZIVM-OUT3.UNI-MUENSTER.DE
	[128.176.192.18])
	by mx1.freebsd.org (Postfix) with ESMTP id 92FFC8FC19;
	Fri, 24 Jul 2009 10:42:37 +0000 (UTC)
	(envelope-from a_best01@uni-muenster.de)
X-IronPort-AV: E=Sophos;i="4.43,262,1246831200"; 
   d="scan'208";a="9278652"
Received: from zivmaildisp2.uni-muenster.de (HELO
	ZIVMAILUSER01.UNI-MUENSTER.DE) ([128.176.188.143])
	by zivm-relay3.uni-muenster.de with ESMTP; 24 Jul 2009 12:42:34 +0200
Received: by ZIVMAILUSER01.UNI-MUENSTER.DE (Postfix, from userid 149459)
	id 8EDCF1B0765; Fri, 24 Jul 2009 12:42:34 +0200 (CEST)
Date: Fri, 24 Jul 2009 12:42:34 +0200 (CEST)
From: Alexander Best <alexbestms@math.uni-muenster.de>
Sender: <a_best01@uni-muenster.de>
Organization: Westfaelische Wilhelms-Universitaet Muenster
To: John Baldwin <jhb@freebsd.org>,
 <freebsd-hackers@freebsd.org>
Message-ID: <permail-20090724104234f0889e8400006fa9-a_best01@message-id.uni-muenster.de>
In-Reply-To: <200907230833.43021.jhb@freebsd.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Cc: Alexey Shuvaev <shuvaev@physik.uni-wuerzburg.de>
Subject: Re: checking number of parallel ports installed and their port
 adresses
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Fri, 24 Jul 2009 10:42:38 -0000

thanks for the hint.

if spent a bit of time and turned the in/out opcodes to ppi ioctls. actually i
was very surprised about the results since you said the overhead wouldn't be
that big.

uploading a 256 kbyte file i got the following results:

using ppi: 17.120 seconds
using in/out opcodes: 8.001 seconds

so i think i'll rather stick to my old inline assembly code even if it can't
be considered nice programming style, but the ppi overhead isn't something i
can cope with in my app.

cheers.
alex

John Baldwin schrieb am 2009-07-23:
> On Wednesday 22 July 2009 3:31:54 pm Alexander Best wrote:
> > the ppi manual states that using ioctl with /dev/ppi is extremely
> > slow. i need
> > the parallel port to be really fast. i need to communicate with a
> > device that
> > uses asynchronous transfer at a rate of ~ 2 mhz. so i need the full
> > ISA bus
> > speed to be able to push/pull data to/from the parallel port
> > without any
> > delays. timing is really critical. if there's a lot of work to do
> > for the
> > scheduler and the io calls get queued too long the transfer will
> > fail.

> The overhead of ppi is probably in the noise on a modern CPU.  I
> think you
> should be fine with just using ppi(4).

> > actually i meant: how can i check the available parallel ports from
> > within my
> > app? is there a syscall i can use or something like that?

> You can look for ppcX devices perhaps.  The easiest way might be to
> enable
> ppi and look for /dev/ppiX devices in /dev.