On Fri, 22 Aug 2003 11:35, Goswin von Brederlow wrote:
> > A paper on udev was presented at OLS this year, at the URL below you
> > can find a copy in PDF format. Basically it is a way of providing
> > some of the features of devfs but based around using hotplug to
> > create device nodes using mknod under a regular directory. So there
> > is no mountable /dev.
>
> Which means you need certain userspace tools for it to work at all and
> if they fail you are screwed. Also how do you boot without a /dev? You
> need a dummy dev containing any possible root device.
>
> Now that you mention the mounting /dev going away this realy sucks.
MOUNTING /dev is going away. So you will have /dev be a regular directory on
a regular file system with device nodes in it. For booting things will work
the same way that they worked when Linux was first released.
> Doesn't sysfs basically do most of what devfs. Doesn't it know about
> all devices?
I believe that udev uses sysfs among other things.
On Fri, 22 Aug 2003 11:48, Brian May wrote:
> One of the concepts behind devfs is that we could move away from
> the current mapping of /dev/device --> {major,minor} --> kernel driver
> system, and instead have the /dev/device map straight to the driver
> (or something like that, I am just reciting this from memory).
Yes, that would have been the eventual aim. devfs=only was a step in that
direction.
> Have they abandoned this approach?
It seems so.
> > > http://archive.linuxsymposium.org/ols2003/Proceedings/
> > >
> > > As for why it's better than udev. There have been bugs in devfs in
> > > the past related to race conditions. Also devfs requires that the
> > > kernel knows about all the device nodes, whether this is a bug or an
> > > excellent feature is a matter of opinion.
>
> Instead of the kernel knowing about device nodes, it needs to know
> about the {major,minor} mappings.
Correct. Therefore we need 32bit device numbers instead.
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