From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754933AbbAHXZN (ORCPT ); Thu, 8 Jan 2015 18:25:13 -0500 Received: from mail-qg0-f42.google.com ([209.85.192.42]:34208 "EHLO mail-qg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752592AbbAHXZK (ORCPT ); Thu, 8 Jan 2015 18:25:10 -0500 Message-ID: <54AF11CF.9080600@hurleysoftware.com> Date: Thu, 08 Jan 2015 18:25:03 -0500 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: One Thousand Gnomes , Arnd Bergmann CC: Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sebastian Andrzej Siewior , Tony Lindgren , Grant Likely Subject: Re: [PATCH] serial: 8250: Make ISA ports optional References: <1420513785-23660-1-git-send-email-peter@hurleysoftware.com> <20150108131008.16c9a31c@lxorguk.ukuu.org.uk> <54AEAC47.1040403@hurleysoftware.com> <1896224.oMI8M6J5T7@wuerfel> <20150108223626.43fd93d5@lxorguk.ukuu.org.uk> In-Reply-To: <20150108223626.43fd93d5@lxorguk.ukuu.org.uk> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/08/2015 05:36 PM, One Thousand Gnomes wrote: >> One idea that has come up in the past but never saw an implementation >> is to make the ttyS namespace and minor numbers completely generic and >> let any serial port driver use it. This would be a major rework, but >> have the added advantage of cleaning up a number of other namespace >> issues as well. There also lots of open question, in particular how >> to maintain compatibility with existing drivers. One could imagine >> that each uart always gets a ttyS device and optionally also gets >> a device node for the same port with a driver specific chardev as >> most of them do today. Or it could be an either/or decision that is >> made at compile time or as a module parameter. > > I'm not sure we should use ttyS for it. ttyS means 8250, a lot of > existing code knows what ttyS is and what sort of ioctls and the like are > assumed. That genie has already escaped the bottle. ./arch/powerpc/platforms/powermac/setup.c: char *devname = "ttyS"; ./arch/powerpc/platforms/chrp/setup.c: add_preferred_console("ttyS", 0, NULL); ./arch/powerpc/kernel/legacy_serial.c: return add_preferred_console("ttyS", offset, opt); ./arch/xtensa/platforms/iss/console.c: serial_driver->name = "ttyS"; ./arch/mips/sni/setup.c: add_preferred_console("ttyS", port, ./arch/mips/sgi-ip32/ip32-setup.c: add_preferred_console("ttyS", *(con + 1) == '2' ? 1 : 0, ./arch/mips/jazz/setup.c: add_preferred_console("ttyS", 0, "9600"); ./arch/mips/sgi-ip22/ip22-setup.c: add_preferred_console("ttyS", *(ctype + 1) == '2' ? 1 : 0, ./arch/arm/mach-davinci/board-da830-evm.c: return add_preferred_console("ttyS", 2, "115200"); ./arch/arm/mach-davinci/board-mityomapl138.c: return add_preferred_console("ttyS", 1, "115200"); ./arch/arm/mach-davinci/board-da850-evm.c: return add_preferred_console("ttyS", 2, "115200"); ./arch/arm/mach-davinci/board-omapl138-hawk.c: return add_preferred_console("ttyS", 2, "115200"); ./arch/cris/arch-v10/kernel/debugport.c: name : "ttyS", ./arch/ia64/hp/sim/simserial.c: hp_simserial_driver->name = "ttyS"; ./arch/um/drivers/ssl.c: .device_name = "ttyS", ./arch/s390/kernel/setup.c: add_preferred_console("ttyS", 1, NULL); ./drivers/tty/amiserial.c: .name = "ttyS", ./drivers/tty/serial/serial_txx9.c:#define TXX9_TTY_NAME "ttyS" ./drivers/tty/serial/sunsab.c: .dev_name = "ttyS", ./drivers/tty/serial/mcf.c: .dev_name = "ttyS", ./drivers/tty/serial/atmel_serial.c:#define ATMEL_DEVICENAME "ttyS" ./drivers/tty/serial/bcm63xx_uart.c: .dev_name = "ttyS", ./drivers/tty/serial/sunsu.c: .dev_name = "ttyS", ./drivers/tty/serial/mrst_max3110.c: .dev_name = "ttyS", ./drivers/tty/serial/apbuart.c: .name = "ttyS", ./drivers/tty/serial/apbuart.c: .dev_name = "ttyS", ./drivers/tty/serial/tilegx.c:#define TILEGX_UART_NAME "ttyS" ./drivers/tty/serial/pmac_zilog.c:#define PMACZILOG_NAME "ttyS" ./drivers/tty/serial/pnx8xxx_uart.c: .dev_name = "ttyS", ./drivers/tty/serial/m32r_sio.c: .dev_name = "ttyS", ./drivers/tty/serial/ip22zilog.c: .dev_name = "ttyS", ./drivers/tty/serial/zs.c: .dev_name = "ttyS", ./drivers/tty/serial/68328serial.c: serial_driver->name = "ttyS"; ./drivers/tty/serial/crisv10.c: driver->name = "ttyS"; /drivers/tty/serial/8250/8250_core.c: .dev_name = "ttyS", ./drivers/tty/serial/sunzilog.c: .dev_name = "ttyS", ./drivers/tty/serial/pxa.c: .dev_name = "ttyS", ./drivers/tty/serial/dz.c: .dev_name = "ttyS", ./drivers/tty/serial/sunhv.c: .dev_name = "ttyS", ./drivers/s390/char/sclp_vt220.c:#define SCLP_VT220_CONSOLE_NAME "ttyS" ./drivers/s390/char/sclp_con.c:#define sclp_console_name "ttyS" ./drivers/s390/char/con3215.c: driver->name = "ttyS"; Besides, despite its pedigree, omap is no closer to 8250 than anything else in drivers/tty/serial/ > A generic namespace needs not to be attached to a legacy naming > > (eg also put all serial ports in /dev/serial/0 /dev/serial/1 etc either > via the tty layer or via systemd/udev) This doesn't address pre-init. Regards, Peter Hurley