[Fwd: Re: [linux-cifs-client] Re: RFC 1001/1002 support]

Juan Lang juan_lang at yahoo.com
Mon Apr 26 21:55:03 GMT 2004


--- Steve French <smfltc at us.ibm.com> wrote:
> Issue two is at least easier to deal with.  The cifs
> vfs is
> mostly LGPL, and in any case would be accessed
> across the
> system call API rather than linked, and it make
> sense
> to think of the cifs vfs as providing a lower level
> API.

Yeah, as long as it's in the kernel I think we can
access it from userspace with impunity, whether it's
GPL or LGPL (or BSD or proprietary).

> Named pipes should not be too hard to implement in
> cifs vfs - they show up in the file name space (in
> Linux) a
> bit differently than os/2 or windows or dos but
> open/read/write 
> over the wire are quite similar to standard file i/o
> (there are a few
> differences requiring specialized transact calls,
> and of course seek and
> a few other ops are forbidden).  I just haven't
> tried to test them.

Being able to do so would be tremendous for Wine. 
This is, in fact, probably more interesting than file
I/O, since we can tell people to use the cifs vfs for
file access rather than trying to do that from Wine. 
Being able to do named pipes, and especially to run
RPCs on them, would boost Wine's interoperability with
existing Windows sytems a great deal.

There are a few special cases of transact, too:  RAP's
somewhat of an oddity.  It isn't stricly necessary
that this show up in the cifs vfs, though, since we
can probably do enough RAP to implement the network
neighborwood browser in userspace.

> Have you thought of what calling convention you
> would like and whether
> you want to treat them as a special case of Unix
> pipe?

No, I haven't given this any thought.  I'll repeat
what I've read elsewhere, that there are two special
features of named pipes that don't have a Unix
equivalent yet:  1) When a pipe is in message mode,
the message length must be preserved.  2) An existing
pipe must be able to be changed from message mode to
byte mode and vice-versa, and that state must stay
with it.  If that can be done with some small
modifications to the Unix pipe api, that's fine with
me.

Mike, you got anything to add here?
--Juan


	
		
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