Re: st(4) and mt eom

[Frank Kardel <kardel%netbsd.org@localhost>]

Hi Adrian!

I just finished implementing the EOM fix. On SPACE(EOM) a READ 
POSITION(LONG_FORMAT) is

done and current file number is set to the number of filemarks since BOT

which is what we need.

on a 10 file taoe (LTO6) both commands

mt fsf 64

mt eom

now return a current file number of 10.

no additional changes to mt like adding a locate command are needed, 
Though adding LOCATE might also be an option to be added separately for 
mt even if it does not help with bacula at all as bacula uses the MT 
ioctls directly and not via scripts.

Thanks for the hint anyway.

Frank


On 03/20/19 21:09, Adrian Bocaniciu wrote:
> On Wed, 20 Mar 2019 20:08:17 +0100
> Frank Kardel <kardel%netbsd.org@localhost> wrote:
>
> > This seems to be a long standing deficiency of the driver. Looking at
> > the SCSI spec it is recommended to issue a READ POSITION command
> >
> > get the current position. Looking at the spec and code it should be
> > possible to handle the SP_EOM case better with respect to the position
> > information
>
> I suggest that you should look at what FreeBSD does for the command:
> mt locate -e
>
> I have not attempted to use NetBSD with a tape, but I am using FreeBSD with an LTO-7 drive and "mt locate -e" works flawlessly.
>
> I always follow that command in my scripts with a "mt rdspos", to verify that it worked correctly, by comparing the result with the last written position on that tape (the position after "mt locate -e" should be the position read after writing the previous last file + 1).
>
> Best regards !