Date: Tue, 20 May 2003 15:44:00 +0200
From: Roger Luethi <rl@hellgate.ch>
To: Pawan Deepika <pawan_deepika@yahoo.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [linux 2.4.18] via-rhine.c
Message-ID: <20030520134400.GB25041@k3.hellgate.ch>
Mail-Followup-To: Pawan Deepika <pawan_deepika@yahoo.com>,
	linux-kernel <linux-kernel@vger.kernel.org>
References: <20030519194317.20999.qmail@web41606.mail.yahoo.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20030519194317.20999.qmail@web41606.mail.yahoo.com>
User-Agent: Mutt/1.3.27i
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1107
Lines: 30

You should ask this kind of questions on the kernelnewbies list.

On Mon, 19 May 2003 12:43:17 -0700, Pawan Deepika wrote:
> through the source code in via-rhine.c. What I
> understand till now is that in Memory-mapped devices,
> I/O operation is performed using
> read(b/w/l)/write(b/w/l) functions while in IO mapped
> devices it is done using in/out(b/w/l). Am I right?

What you do with inb etc. is called PIO (Programmed I/O).

> But in via-rhine.c I notice use of inb and outb even
> in memory mapped case(code is shown below)
> 
> ------------------------------------------------------
> #ifdef USE_MEM
> 530 static void __devinit enable_mmio(long ioaddr, int
> chip_id)
> 531 {

It does exactly what the function name says: it uses PIO to flip a bit in
some register to enable MMIO, which is just a different (and better) way to
transfer the data.

Roger
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/