Message-ID: <20030519194317.20999.qmail@web41606.mail.yahoo.com>
Date: Mon, 19 May 2003 12:43:17 -0700 (PDT)
From: Pawan Deepika <pawan_deepika@yahoo.com>
Subject: [linux 2.4.18] via-rhine.c
To: linux-kernel <linux-kernel@vger.kernel.org>
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Hi,

 I am learning device driver only now. I was going
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?

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 {
532         int n;
533         if (chip_id == VT3043 || chip_id ==
VT86C100A) {
534                 /* More recent docs say that this
bit is reserved ... */
535                 n = inb(ioaddr + ConfigA) | 0x20;
536                 outb(n, ioaddr + ConfigA);
537         } else if (chip_id == VT6102) {
538                 n = inb(ioaddr + ConfigD) | 0x80;
539                 outb(n, ioaddr + ConfigD);
540         }
541 }
542 #endif
-----------------------------------------------------

Can anyone tell me how does it work here? Also, don't
we need to allocate I/O ports(using request_region() )
before performing any inb/outb operations?

Please advise.

Thanks & regards,
Deepika

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