From owner-freebsd-hackers Sun Nov 30 11:03:04 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id LAA25503 for hackers-outgoing; Sun, 30 Nov 1997 11:03:04 -0800 (PST) (envelope-from owner-freebsd-hackers) Received: from ns2.cetlink.net (root@ns2.cetlink.net [209.54.54.20]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id LAA25448 for ; Sun, 30 Nov 1997 11:02:54 -0800 (PST) (envelope-from jak@cetlink.net) Received: from hot1.auctionfever.com (ts1-cltnc-46.cetlink.net [209.54.58.46]) by ns2.cetlink.net (8.8.5/8.8.5) with SMTP id OAA14503; Sun, 30 Nov 1997 14:02:31 -0500 (EST) From: jak@cetlink.net (John Kelly) To: John-Mark Gurney Cc: Bruce Evans , hackers@freebsd.org Subject: Re: 650 UART, SIO driver, 8259 PIC Date: Sun, 30 Nov 1997 20:03:35 GMT Message-ID: <3484c18f.19943322@mail.cetlink.net> References: <199711301019.VAA09201@godzilla.zeta.org.au> <19971130030719.29570@hydrogen.nike.efn.org> In-Reply-To: <19971130030719.29570@hydrogen.nike.efn.org> X-Mailer: Forte Agent 1.01/16.397 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by hub.freebsd.org id LAA25468 Sender: owner-freebsd-hackers@freebsd.org X-Loop: FreeBSD.org Precedence: bulk On Sun, 30 Nov 1997 03:07:19 -0800, John-Mark Gurney wrote: >ok, I see what you mean.. :) that's good news, but it still doesn't >force that the ports be in proper order... we'll just have to document >it this way if they want their AST/4 port board working.. just hope that >people won't complain because they didn't have their setup correct in >the first place.. In the section discussing IRQ control and status registers, the man page only mentions four ports per interrupt sharing "group." It also says that "control and status registers for a group, if any, must be mapped to the scratch register (register 7) of a port in the group. Such a port is called a master port." With only eight bits in the scratch register, mapping both a control and status register to it will limit your interrupt sharing group to a maximum of four ports. A software design based on that hardware configuration seems too restrictive. Eight port boards which share a single IRQ are common now. The board I have does not even use the idea of mapping. You simply jumper it to select an unused I/O address where the status port will appear. It renders obsolete the idea of a "master" port. John