[Buildroot] editing device_table_dev.txt
thomas.petazzoni at free-electrons.com
Sun Feb 24 17:26:20 UTC 2013
Dear Arnout Vandecappelle,
On Fri, 22 Feb 2013 00:24:11 +0100, Arnout Vandecappelle wrote:
> > What you mean that mdev or udev does not create device nodes ???
> > If older kernels don't support devtmpfs like Baruch
> > said then who does that device node creation if not the mdev or udev
> > when event happens ???
> Well, nobody...
> Turns out that mdev still does device node creation. Makes me
> wonder if I'm not mistaken about udev as well... I just remember
> hearing that device node creation was removed when DEVTMPFS was
Yes, I think you got the thing wrong: udev and mdev are still creating
the device nodes. Of course, they might have already been created by
devtmpfs, but I don't think it is a requirement. At least, devtmpfs is
definitely not a requirement for mdev to work (except in Buildroot, in
which we made the decision that if mdev is to be used, then devtmpfs
support must be there).
> >> That said, you can create custom mdev/udev rules to create device
> >> nodes. But it's all manual - and much simpler to just create the
> >> device nodes manually.
> > for mdev it's just a single file, /etc/mdev.conf (I can even
> > copy-paste it here, it's not that long and will cover 99% of needs).
> Yes, but that file just specifies the chmod/chown rules, not how to
> create the device nodes. But as I just saw in the code, mdev does in
> fact create the device nodes.
udev can also create symbolic links to device files based on custom
rules, or other funky things.
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
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