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/dev/usema questions

To: (Linux/SGI list)
Subject: /dev/usema questions
From: Mike Shaver <>
Date: Sun, 10 Aug 1997 22:50:35 -0400 (EDT)
Couple of questions I'd like some enlightenment on, as I try to get
/dev/usema{,clone} ready for Miguel's Xcellent Adventure:

- what is us_attach.us_handle for?  Is it some opaque pointer I can
send to userland and get back for all the other ioctls?  Please? =)

- do libc and IRIX really use the minor of the filehandle to identify
the usema `device' it's working with?

- from sys/usioctl.h:
#define UIOCBLOCK       (UIOC|3)        /* block, sync, intr */
#define UIOCNOIBLOCK    (UIOC|5)        /* block, sync, intr */
Should I take UIOCNOIBLOCK to really be "/* block, sync, nointr */"?

- what's the difference between sync/async blocking/unblocking?  I
thought it might be that sync would mean that schedule() happened
immediately, but then I don't think that async blocking makes much

The us* stuff is pretty cool, I must say.  Someone (<whistles
quietly>) should think about doing it for Linux...


#> Mike Shaver (      Information Warfare Division  
#> Chief Tactical and Strategic Officer         "Saepe fidelis"        
#> "I like your game, but we have to change the rules." -- Anon        

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