linux-kernel - Re: linux kernel without file system

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Message-Id: <1231940972.11907.49.camel@skunk>
Date:	Wed, 14 Jan 2009 14:49:32 +0100
From:	Xavier Bestel <xavier.bestel@...e.fr>
To:	Kay Sievers <kay.sievers@...y.org>
Cc:	Philippe De Muyter <phdm@...qel.be>,
	Tomasz Chmielewski <mangoo@...g.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: linux kernel without file system

Oh yes sorry, I mixed that with the dev entry in sysfs, which contains
the device major:minor in textual form (e.g. /sys/block/fd0/dev).
Confused memory ...

	Xav

On Wed, 2009-01-14 at 11:34 +0100, Kay Sievers wrote:
> On Wed, Jan 14, 2009 at 10:52, Xavier Bestel <xavier.bestel@...e.fr> wrote:
> > On Wed, 2009-01-14 at 10:34 +0100, Philippe De Muyter wrote:
> >> On Wed, Jan 14, 2009 at 09:46:48AM +0100, Tomasz Chmielewski wrote:
> >> >> I need to design a very small embedded system that must only control
> >> >> one ethernet port and two serial lines and must fit in a very small flash
> >> >> memory.  So I thought about replacing the call to /etc/init by my
> >> >> application
> >> >> program and removing all the file-system part of linux.
> >> >> Is that doable ?
> >> >> Is there a 'standard' way of doing that ?
> >> >> The first problem I see is accessing my serial lines.  How could I do that
> >> >> without using open("/dev/ttySx"), which requires a file system ?
> >> >> Is there a way to access devices that does not require a file-system ?
> >> >
> >> > You could put everything in initramfs (and embed it in the kernel).
> >>
> >> Actually, I was thinking about reducing the footprint of my kernel by
> >> removing all the fs-related system calls, so the problem is not where
> >> the file-system is, but how to access (serial) devices without giving their
> >> "/dev/..." name.
> >
> > You can still mount sysfs somewhere and access the device nodes from
> > there.
> 
> There are no device nodes in sysfs to talk to the device, only
> attributes, which are mostly plain small text files. For some devices
> there are a few writable and mappable files which can change the
> device's state, but that's nothing like a device node.
> 
> Kay
> 


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