Re: Device enumeration (was Re: CD writing in future Linux (stirring up a hornets' nest))

[Michael Tokarev <mjt@tls.msk.ru>]

Olivier Galibert wrote:
[]
> 4- sysfs has all the information you need, just read it
[]
> Answer 4 would be very nice if it was correct.  sysfs is pretty much
> mandatory at that point, and modulo some fixable incompleteness
> provides all the capability information and model names and everything
> needed to find the useful devices.  What it does not provide is the
> mapping between a device as found in sysfs, and a device node you can
> open to talk to the device.  You get the major/minor, which allows you
> to create a temporary device node iff you're root.  Or you can scan
> all the nodes in /dev to find the one to open, which is kinda
> ridiculous and inefficient.  Or you have to go back to udev/hal to ask
> for the sysfs node/device node path mapping, and then why use sysfs in
> the first place.

That's exactly the point why I always wanted to have automatic minimal-devfs-
alike in kernel, similar to ndevfs but complete: so that kernel names of
defices are *always* present in /dev, regardless of the presense of udev or
something else.  All the rest - udev, device permissions, "alternative"
names (like /dev/cdrom etc) can be built on top of that "kernel naming scheme",
but the key point is that we *always* have a device in /dev/ named exactly
the same as kernel "thinks" of it - so eg, /proc/partitions, dmesg output,
sysfs scanning etc etc will produce real and useful results.

But oh.. Am I starting new [n]devfs flamewar?

/mjt