Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!cwjcc!hal!ncoast!allbery
From: allbery@NCoast.ORG (Brandon S. Allbery)
Newsgroups: comp.unix.wizards
Subject: Re: How do I tell physio that my device has reached EOF?
Message-ID: <1989Nov17.004138.4551@NCoast.ORG>
Date: 17 Nov 89 00:41:38 GMT
References: <6705@portia.Stanford.EDU>
Reply-To: allbery@ncoast.ORG (Brandon S. Allbery)
Followup-To: comp.unix.wizards
Organization: North Coast Public Access UN*X, Cleveland, OH
Lines: 25

As quoted from <6705@portia.Stanford.EDU> by name@portia.Stanford.EDU (tony cooper):
+---------------
| In the context of a raw device driver for a tape drive, physio() tells
| my strategy routine to schedule that 16 blocks of data be put into a
| buf buffer. My device transfers 14 blocks then reaches EOF. My question
| is this: How do I report back to physio() that 14 blocks have been put
| into the buf structure and that EOF has been reached.
+---------------

Combining your posting with my experience with this on the user-process end, I
conclude that your driver must remember that it hit EOF and report transfer-
ring 0 blocks on subsequent calls or until the driver is sent a command to
advance to the next file on the tape.

Related or not I don't know, not being a kernel hack, but:  from the user
process end, read() works this same way.  The last block in a file returns a
short count, then 0 is returned by subsequent reads.

++Brandon
-- 
Brandon S. Allbery    allbery@NCoast.ORG, BALLBERY (MCI Mail), ALLBERY (Delphi)
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