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From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: comp.unix.wizards
Subject: Re: /dev/stdin for 4.3?
Message-ID: <823@mcgill-vision.UUCP>
Date: Fri, 26-Jun-87 05:04:21 EDT
Article-I.D.: mcgill-v.823
Posted: Fri Jun 26 05:04:21 1987
Date-Received: Sat, 4-Jul-87 22:55:27 EDT
References: <7359@brl-adm.ARPA> <5856@brl-smoke.ARPA> <15318@onfcanim.UUCP> <302@jpusa1.UUCP>
Organization: McGill University, Montreal
Lines: 59

In article <302@jpusa1.UUCP>, stu@jpusa1.UUCP (Stu Heiss) writes:
> In article <7036@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
>> In article <792@mcgill-vision.UUCP> mouse@mcgill-vision.UUCP (der Mouse)
>> gives an implementation of the `open' routine for the /dev/fd/n
>> driver.  His has an interesting bug.

Indeed it does.  Thanks for catching that one, Chris.

>> This should not in fact break anything,

True, assuming you did in fact put nodev in the read and write slots of
the cdevsw entry.

> C'mon guys, don't leave us in the dark!  I was about to install
> Mouse's 'driver' and don't recall seeing anything by Fred Blonder.

Neither do I, for that matter, but I wasn't watching closely 'cause
I've already *got* such a driver.

> Give us a working driver, please.

Well, actually the original worked, it's just that one particular error
case wasn't being caught quite soon enough, and resulted in a
successful open() and then failing read()s and/or write()s.

> This seems trivial for you kernal wizards.  Chris, Mouse, can you
> help?

Once noticed, it is simple to fix.  (This patch also changes a NULL to
a 0, because I have quit trusting people responsible for C system
maintenence to define NULL correctly.  In this case, it's OK 'cause
this is rather BSD-specific, but it can't hurt anything.)

*** stdiodev.c=	Fri Nov 21 04:45:25 1986
--- stdiodev.c	Fri Jun 26 04:51:27 1987
***************
*** 19,25 ****
   if ((fd < 0) || (fd >= NOFILE))
    { return(EBADF);
    }
!  if (u.u_ofile[fd] == NULL)
    { return(ENXIO);
    }
   if ((mode&FREAD) && !(u.u_ofile[fd]->f_flag&FREAD))
--- 19,28 ----
   if ((fd < 0) || (fd >= NOFILE))
    { return(EBADF);
    }
!  if (fd == rfd)
!   { return(ENXIO);
!   }
!  if (u.u_ofile[fd] == 0)
    { return(ENXIO);
    }
   if ((mode&FREAD) && !(u.u_ofile[fd]->f_flag&FREAD))

					der Mouse

				(mouse@mcgill-vision.uucp)