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SubjectRe: UUIDs (and devfs and major/minor numbers)
On Mon, 21 Jun 1999, Brandon S. Allbery KF8NH wrote:
> In message <Pine.LNX.4.05.9906210748380.11093-100000@mhw.ULib.IUPUI.Edu>, "Mark
> H. Wood" writes:
> +-----
> | > | devfs detractor either; at most I've asked people to consider whether a
> | > | filesystem hierarchy is really the most appropriate representation for th
> | e
> | > | various information that we all want.
> | >
> | > Why wouldn't it be? In its most generalized form, a filesystem is a
> | > hierarchical database used for kernel-to-userspace communication, which is
> | > why Plan 9 generalized it to namespaces and why there is e.g. /proc. It
> |
> | Besides, there's nothing that guarantees a filesystem *must* be
> | hierarchial. You could have tagging metadata and a QBE filespec syntax if
> | you really wanted to. (I can't yet imagine wanting to.) Hierarchy wasn't
> | inherent in the TOPS-10 filesystem, for example; it was grafted in later
> | because it is, after all, quite useful. Early MSDOS was the same way, I
> | believe.
> +--->8
>
> But there is still a hierarchy, just under another name. "Show me all CDROM
> devices" defines a hierarchy based on device type. "Show me all SCSI
> devices" defines one based on the bus the device is on.

The point is that these hierarchies are all in your mind, and that what is
in your mind and what is in my mind may not be the same. Give the
programmer the tools to impose the hierarchy he needs at runtime, instead
of picking one at design time.

> Unless you're suggesting that the enumerator generate all devices and let
> userspace cope with the result --- which seems needlessly expensive: a
> system call (whether it's sysctl() or read() wouldn't matter) per device,
> when searching for only a small subset of devices.

The enumerator can be as smart as you care to make it. Just remember that
a decision that I may think of as smart, may seem really stupid to you.
Why not find a way to put off the decision until we know which way it
should go?

--
Mark H. Wood, Lead System Programmer mwood@IUPUI.Edu
Specializing in unusual perspectives for more than twenty years.


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