Date: Mon, 13 Feb 2006 09:50:46 -0800
From: Greg KH <greg@kroah.com>
To: Olivier Galibert <galibert@pobox.com>, linux-kernel@vger.kernel.org
Subject: Re: CD writing in future Linux (stirring up a hornets' nest)
Message-ID: <20060213175046.GA20952@kroah.com>
References: <20060125173127.GR4212@suse.de> <43D7C1DF.1070606@gmx.de> <878xt3rfjc.fsf@amaterasu.srvr.nix> <43ED005F.5060804@tmr.com> <20060210235654.GA22512@kroah.com> <20060212120450.GA93069@dspnet.fr.eu.org> <20060212164633.GA2941@kroah.com> <20060212211406.GA48606@dspnet.fr.eu.org> <20060213062412.GB2335@kroah.com> <20060213164911.GB75835@dspnet.fr.eu.org>
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On Mon, Feb 13, 2006 at 05:49:11PM +0100, Olivier Galibert wrote:
> On Sun, Feb 12, 2006 at 10:24:12PM -0800, Greg KH wrote:
> > On Sun, Feb 12, 2006 at 10:14:06PM +0100, Olivier Galibert wrote:
> > > On Sun, Feb 12, 2006 at 08:46:33AM -0800, Greg KH wrote:
> > > > On Sun, Feb 12, 2006 at 01:04:51PM +0100, Olivier Galibert wrote:
> > > > > You need to call udevinfo for that, or parse /dev/.udev/*.  Do you
> > > > > think it would be possible to have hotplug/udev/whatever exists in the
> > > > > future to give that information back in the kernel and have it appear
> > > > > in sysfs?
> > > > 
> > > > No.  Why would it when it is very simple to query udevinfo for that?
> > > 
> > > In order not to depend on a userland package for the kernel service of
> > > device enumeration?  It's udevinfo now, what will it be in two years?
> > 
> > WTF?  You are depending on that same program to create your device
> > nodes.  If you don't want to use that program to do it, then use
> > something else, or use a static device tree, which works like always.
> 
> Funnily enough, my, say, mp3 usb key sync system would like to run as
> non-root and does not want to know or care about what program creates
> the device nodes.  Too bad this otherwise beautiful and useful sysfs
> is crippled by design.

Huh?  What sysfs design flaw is that?

You can run your mp3 usb ksy sync system as non-root just fine, I do
just that.  When my device is plugged in, a udev rule runs a script that
changes users and resyncs my device.

But that has nothing to do with sysfs at all.

> > sysfs exports everything that userspace needs to know, if it wants to
> > create a device node to talk to that specific device.  udev used it to
> > create your /dev tree, while other programs use it to create temporary
> > device nodes to do other things to your devices.  Either way, the kernel
> > doesn't know, or care what you call those device nodes.
> 
> You mean root is mandatory to talk with devices, whatever they are?

Not at all.  You only have to be root to create a device node, nothing
new there.

thanks,

greg k-h
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