the semantics that were being discussed were at the VFS level, and
poll is part of the implementation of a specific file system.
when i think about this, the purpose of the event notification is not
to tell you what changed, but that a change occured. figuring out what
happened in detail requires that the FS support some inquiry method,
but the notification that someone called write() with a given
descriptor is something that i think should exist at a level above the
individual FS's: ie. VFS.
one could argue that a three-step process is inefficient
(ie. kernel->user "change occured"; user->kernel "what happened ?";
kernel->user "event type XXXX"). However, given that write(), unlink()
and ioctl() are the only (?) system calls that can alter the contents of a
file, its not hard to avoid this by providing hooks for each one.
this has all kinds of nice potential uses, particularly with ioctl()
support.
--p (echoes of scheduler activations ringing around here ...)
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