Re: [gentoo-dev] devfs is dead, let's move on

[Martin Schlemmer <azarah@gentoo.org>]

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On Wed, 2005-07-06 at 15:46 -0700, Greg KH wrote:
> Ok, now that devfs is removed from the 2.6 kernel tree[1], I think it's
> time to start to revisit some of the /dev naming rules that we currently
> are living with[2].
> 
> To start with, the 061 version of udev offers a big memory savings if
> you use the "default" kernel name of a device[3].  If you do that, it does
> not create a file in its database in /dev/.udevdb/
> 
> If we can move away from some of our devfs-like names, we stand to
> reclaim a lot of memory from everyone's machines.  As an example, if we
> drop all of the tty/pts/vc/vcc symlinks, and just go with the default
> kernel name, we save 2.5Mb of space in tempfs/ramfs.  I've done this on
> my machines and everything seems to work just fine (it looks like
> everything that was trying to use a tty node was just using the symlink
> anyway.)
> 
> So, anyone have any objections to me changing the default udev naming
> scheme in this manner?
> 

Fine with me.  I assume we will need to keep the rcscript support for
those die-hard 2.4 users still, but hopefully we can eventually drop
that as well.

> Next up, that loony block device naming scheme (more on that later...)
> 

Heh.  I hope that we will still at least just do the cdsymlinks stuff
(just the /dev/cdrom, /dev/dvd, etc stuff) as that do make things a bit
easier for multimedia stuff.


> [3] HAL needs a patch to be able to handle this.  It's posted on the
>     hal development mailing lists and will be checked in real-soon-now.

I just think we need to make sure this is in first ...


Lastly on an unrelated note ... I have a rule:

-----
# cat /etc/udev/rules.d/40-dm.rules
KERNEL="dm-[0-9]*", PROGRAM="/sbin/devmap_name %M %m", NAME="mapper/%c", SYMLINK="%c"
-----

And in theory it should be the last rule to set the name ... however the
default one in 50-udev.rules overrides it, and I have to add
OPTIONS="last_rule"

--- (default rule) ---
KERNEL="dm-[0-9]*",     NAME=""
----------------------

I am assuming (without having looked at the code) that because NAME is
set to "", whatever code that should drop it as it have NAME, does not
kick in?


Thanks,

-- 
Martin Schlemmer
Gentoo Linux Developer, Desktop/System Team Developer
Cape Town, South Africa


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