Re: port-amd64/53890: st(4) driver for tapes not working o variable block size

[mlelstv%serpens.de@localhost (Michael van Elst)]

The following reply was made to PR port-amd64/53890; it has been noted by GNATS.

From: mlelstv%serpens.de@localhost (Michael van Elst)
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: port-amd64/53890: st(4) driver for tapes not working o variable block size
Date: Sat, 19 Jan 2019 14:42:42 -0000 (UTC)

 pa0gri%amsat.org@localhost ("G J van der Grinten") writes:
 
 >But on the recond read for a block I get an " Invalid argument" and that is
 >invalid by itself.
 
 Looks like this is not the tape driver itself. The kernel physio() routine
 does a sanity check on the I/O byte offset to be a multiple of DEV_BSIZE
 (== 512 bytes) and returns EINVAL if that's false. That's why the
 second read or write fails (the first starts at offset 0).
 
 That sanity check doesn't make sense for a tape and might not even be needed
 for e.g. a disk, the disk drivers do their own checks.
 
 -- 
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                                 Michael van Elst
 Internet: mlelstv%serpens.de@localhost
                                 "A potential Snark may lurk in every tree."