Re: LANANA: To Pending Device Number Registrants

[H. Peter Anvin]

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

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