From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932557AbWFKDGi (ORCPT ); Sat, 10 Jun 2006 23:06:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932560AbWFKDGi (ORCPT ); Sat, 10 Jun 2006 23:06:38 -0400 Received: from xenotime.net ([66.160.160.81]:58260 "HELO xenotime.net") by vger.kernel.org with SMTP id S932557AbWFKDGh (ORCPT ); Sat, 10 Jun 2006 23:06:37 -0400 Date: Sat, 10 Jun 2006 20:09:22 -0700 From: "Randy.Dunlap" To: "Antonino A. Daplas" Cc: jonsmirl@gmail.com, akpm@osdl.org, linux-fbdev-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, greg@kroah.com Subject: Re: [PATCH 5/5] VT binding: Add new doc file describing the feature Message-Id: <20060610200922.a93c3c72.rdunlap@xenotime.net> In-Reply-To: <448B61F9.4060507@gmail.com> References: <44893407.4020507@gmail.com> <9e4733910606092253n7fe4e074xe54eaec0fe4149f3@mail.gmail.com> <448AC8BE.7090202@gmail.com> <9e4733910606100916r74615af8i34d37f323414034c@mail.gmail.com> <448B38F8.2000402@gmail.com> <9e4733910606101644j79b3d8a5ud7431564f4f42c7f@mail.gmail.com> <448B61F9.4060507@gmail.com> Organization: YPO4 X-Mailer: Sylpheed version 2.2.5 (GTK+ 2.8.3; x86_64-unknown-linux-gnu) Mime-Version: 1.0 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 On Sun, 11 Jun 2006 08:21:13 +0800 Antonino A. Daplas wrote: > Jon Smirl wrote: > > On 6/10/06, Antonino A. Daplas wrote: > >> > I may be looking at the problem a little differently. I see the > >> > drivers like fb, vga, etc as registering with the console and saying > >> > they are capable of providing console services. I then see the console > >> > system as opening one of the registered devices. A driver is free to > >> > register/unregister whenever it wants to as long as it isn't open by > >> > the console system. Console can only open one driver at a time. > >> > >> No, this isn't true. You can have multiple console drivers active, > >> that's why you have a first and last parameter in take_over_console(). > >> Thus at boot time, the system driver will take consoles 0 - 63. > >> Later on when a driver loads, it can take over consoles 0 - 7, leaving > >> consoles 8 - 63 to the system driver. > >> > >> To put it another way, console drivers can register for consoles 0 - 63, > >> but the user may choose to use it only for consoles 0 - 7. > >> > >> This is another reason for the system driver, it makes the unbinding > >> behavior predictable. Without a system driver, guessing which driver > >> replaces the just unbound one may become just a tad bit confusing for > >> the typical user. > > > > I find the whole console/tty layer to be quite confusing to talk > > about. I am mixing up console as in where printk goes and console the > > video card login device. The part about making everything equal was > > directed towards the printk output device. > > > > Sorry about that, I probably should use VT or VC for the main topic > of this thread, and plain 'console' for where the printk output goes. > > This illustration might help, though I'm not sure if it's entirely > correct. The main topic of this thread deals with the VT branch only. > > Console > : > :-----:-----------:--- etc > : : : > VT Serial Net > : > :--------:-------:-----etc > : : : > vgacon fbcon newport_con > : : : > : : : > hardware fbdev hardware > : > : > hardware > > > > I see now that you can have tty0-7 assigned to a different console > > driver than tty8-63. > > Why do I want to do this? > > Multi-head. I can have vgacon on the primary card for tty0-7, > fbcon on the secondary card for tty8-16. > > > Why do we need 64 predefined tty devices? > > I don't know, but no one's stopping you to redefine MAX_NR_CONSOLES to > a lower or higher number. > > > > > Googling around the only example I could find was someone with a VGA > > card and a Hercules card. They setup 8 consoles on each card. > > > >> > Over time it would nice if these all merged to a single > >> > interchangeable interface. I would really like to be able to > >> > dynamically switch to serial/net while debugging a video driver. Is > >> > there some fundamental reason why these can't be merged? > >> > >> It's already possible to redirect the system messages to two different > >> console classes, ie with the boot parameter: > >> > >> console=tty0,ttyS0 /* direct output to VT and serial console */ > >> > >> And you can already choose the console you want by adjusting > >> /etc/inittab. > > > > How can I change where printk are going at run-time? I didn't know you > > could do that. > > I really don't know. Maybe we have some kind of entry in /proc somewhere? If not, it should be in /sys(fs) (if being added). fwiw, I have a patch to list all registered consoles: http://www.xenotime.net/linux/patches/consoles-list.patch --- ~Randy