Re: LANANA: To Pending Device Number Registrants

H. Peter Anvin
2001-05-14T19:59:02Z

Jeff Garzik wrote:
>
> "H. Peter Anvin" wrote:
> > Linus Torvalds has requested a moratorium on new device number
> > assignments. His hope is that a new and better method for device space
> > handing will emerge as a result.
>
> Here's my suggestion for a solution.
>
> Once I work through a bunch of net driver problems, I want to release a
> snapshot block device driver (freezes a blkdev in time). For this, I
> needed a block major. After hearing about the device number freeze, I
> was wondering if this solution works:
>
> Register block device using existing API, and obtain a dynamically
> assigned major number. Export a tiny ramfs which lists all device
> nodes. Mounted on /dev/snap, /dev/snap/0 would be the first blkdev for
> snap's dynamically assigned major. (Al Viro said he has skeleton code
> to create such an fs, IIRC)
>
> This solution
> (a) keeps from grot-ing up /proc even more [I had considered
> proc_mknod() until viro talked me out of it]
> (b) does not require centrally assigned majors and minors.
> (c) does not require devfs. most distros ship without it afaik, and
> switching to it is not an overnight process, and requires devfsd to be
> useful in the real world.
>

It does, however, not manage permissions, nor does it provide for a sane
namespace (it exposes too many internal implementation details in the
interface -- in particular, the driver becomes part of the namespace, and
devices move around between drivers regularly.)

-hpa

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."