From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from caramon.arm.linux.org.uk (caramon.arm.linux.org.uk [217.147.92.249]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 76D05DDEB8 for ; Wed, 4 Apr 2007 18:52:15 +1000 (EST) Date: Wed, 4 Apr 2007 09:51:59 +0100 From: Russell King To: Brad Boyer Subject: Re: [PATCH] Stop pmac_zilog from abusing 8250's device numbers. Message-ID: <20070404085159.GB13134@flint.arm.linux.org.uk> References: <1175610345.2665.15.camel@shinybook.infradead.org> <17938.57292.870224.132415@cargo.ozlabs.ibm.com> <1175642916.10567.24.camel@shinybook.infradead.org> <20070403212928.GA12951@cynthia.pants.nu> <1175644642.10567.31.camel@shinybook.infradead.org> <20070403221002.GA13210@cynthia.pants.nu> <1175648051.10567.61.camel@shinybook.infradead.org> <20070403230908.GA13471@cynthia.pants.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20070403230908.GA13471@cynthia.pants.nu> Sender: Russell King Cc: Paul Mackerras , David Woodhouse , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Apr 03, 2007 at 04:09:08PM -0700, Brad Boyer wrote: > The availability of the specific chip in question is a red herring in > my opinion. I do understand that 8250 compatible chips are very common > and are the most likely serial chips to be used with Linux. However, I > will point out that the define is TTY_MAJOR, not 8250_MAJOR. It seems > to me that whoever named it was thinking in more generic terms. You're reading too much into the name. It's historical, and the reason can still be seen in LANANA: 4 char TTY devices 0 = /dev/tty0 Current virtual console 1 = /dev/tty1 First virtual console ... 63 = /dev/tty63 63rd virtual console 64 = /dev/ttyS0 First UART serial port ... 255 = /dev/ttyS191 192nd UART serial port UART serial ports refer to 8250/16450/16550 series devices. When the drivers/char/serial.c driver was written, it was in the very early days of Linux. I'd guess that the major/minor numbers were similar to Minix, thereby allowing a minixfs to be used as the initial filesystem type. Anyway, as you can see, defining chardev major 4 to be "8250_MAJOR" would also be a misnomer because it's used for the virtual consoles, and it's _that_ use for which it (probably) was called TTY_MAJOR. (Note that in the very early days, this major also got used for PTY devices. Since then they've moved to major 2/3 and then we got Unix98 PTY support.) -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: