From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 17 Nov 2000 12:30:52 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 17 Nov 2000 12:30:42 -0500 Received: from panic.ohr.gatech.edu ([130.207.47.194]:62985 "EHLO havoc.gtf.org") by vger.kernel.org with ESMTP id ; Fri, 17 Nov 2000 12:30:34 -0500 Message-ID: <3A156422.7D1D3DBD@mandrakesoft.com> Date: Fri, 17 Nov 2000 12:00:18 -0500 From: Jeff Garzik Organization: MandrakeSoft X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.4.0-test11 i686) X-Accept-Language: en MIME-Version: 1.0 To: Russell King CC: Brian Gerst , linux-kernel@vger.kernel.org, mj@suse.cz Subject: Re: VGA PCI IO port reservations In-Reply-To: <200011171656.QAA01320@raistlin.arm.linux.org.uk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Russell King wrote: > > Brian Gerst writes: > > This is an artifact from the ISA 10-bit IO bus. Many ISA cards do not > > decode all 16 address bits so you get aliases of the 0x100-0x3ff region > > throughout IO space. PCI cards should only use the first 256 ports of > > any 1k block to avoid aliases unless they claim the base alias. For > > example, all the xxe8 addresses for the S3 are aliases of 0x02e8 to an > > ISA card. Video cards are an exception to the general rule because they > > have to support all the legacy VGA crap. > > No. All xxe8 addresses access specific registers. For example: > > 0x9ea8 is the drawing command > 0xa2e8 is the background colour register > 0xa6e8 is the foreground colour register > > So, as you see they aren't aliases. Oh yeah, if you are writing for S3 specifically, you can do 100% MMIO, and simply turn off all I/O decoding. Check out Keith Packard's kdrive/s3trio in the XFree86 tree... Jeff -- Jeff Garzik | Building 1024 | The chief enemy of creativity is "good" sense MandrakeSoft | -- Picasso - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/