Subject: Re: linux kernel without file system
From: Xavier Bestel <xavier.bestel@free.fr>
To: Kay Sievers <kay.sievers@vrfy.org>
Cc: Philippe De Muyter <phdm@macqel.be>, Tomasz Chmielewski <mangoo@wpkg.org>,
       LKML <linux-kernel@vger.kernel.org>
In-Reply-To: <ac3eb2510901140234m29ca516bocd0e7dd997122a7b@mail.gmail.com>
References: <496DA678.1090701@wpkg.org> <20090114093422.GA9771@frolo.macqel>
	 <1231926744.11907.12.camel@skunk>
	 <ac3eb2510901140234m29ca516bocd0e7dd997122a7b@mail.gmail.com>
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Date: Wed, 14 Jan 2009 14:49:32 +0100
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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@free.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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