linux-kernel - Re: Documentation for sysfs, hotplug, and firmware loading.

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Date:	Fri, 20 Jul 2007 23:48:14 -0400
From:	Rob Landley <rob@...dley.net>
To:	Greg KH <greg@...ah.com>
Cc:	Cornelia Huck <cornelia.huck@...ibm.com>,
	Kay Sievers <kay.sievers@...y.org>,
	linux-kernel@...r.kernel.org, Michael-Luke Jones <mlj28@....ac.uk>,
	Krzysztof Halasa <khc@...waw.pl>,
	Rod Whitby <rod@...tby.id.au>,
	Russell King <rmk@....linux.org.uk>, david@...g.hm
Subject: Re: Documentation for sysfs, hotplug, and firmware loading.

On Friday 20 July 2007 4:09:36 am Greg KH wrote:
> On Fri, Jul 20, 2007 at 09:54:01AM +0200, Cornelia Huck wrote:
> > On Fri, 20 Jul 2007 00:00:01 -0700,
> >
> > Greg KH <greg@...ah.com> wrote:
> > > > I don't insist on it, mknod insists on it.  You cannot mknod a dev
> > > > node without specifying block or char.
> > > >
> > > > You're saying that sysfs should provide major and minor numbers
> > > > without anywhere specifying "char" or "block", meaning the major and
> > > > minor numbers cannot be _used_.  I am insisting on getting the third
> > > > piece of information without which "major" and "minor" are useless.
> > > >
> > > > I asked very specifically about this at OLS, several times.  What
> > > > you're telling me now seems to contradict what you told me then.
> > >
> > > Here's the rule:
> > > 	If the SUBSYSTEM is "block", it's a block device.  Otherwise
> > > 	it's a char device.
> >
> > That's actually quite confusing to the casual reader, since:
> > > But also realize that the majority of events you will get have nothing
> > > to do with device nodes.  I think you are forgetting this fact.
> >
> > So the rule should be:
> > 	If the SUBSYSTEM is "block" (implying major/minor are provided),
> > 	it's a block device.
> > 	If the SUBSYSTEM is not "block", and major/minor are provided,
> > 	it's a char device.
> > 	If major/minor are not provided, the event/device is not
> > 	relevant to device node creation.
>
> Yes, that is much more descriptive, thanks.

agreed, thanks.

I'll try to post an updated version of my hotplug documentation later tonight.  
(Just a _touch_ jetlagged at the moment, though.  It may only be 9:47 
california time, but it's 11:47 on the east cost.  I think.)

> greg k-h

Rob
-- 
"One of my most productive days was throwing away 1000 lines of code."
  - Ken Thompson.
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