On Sat, 15 Apr 2000, Eric Lee Green wrote:
...
> Hmm, off-hand, does MTIOCGET have a field that tells the max block size?
> The driver definitely knows the max block size, but does the
> application?
>
No, it does not.
...
> I guess the next little utility I'll write using the generic mtxl SCSI
> library is a utility that scans the SCSI bus looking for tape drives and
> reporting all sorts of neat stuff about them like, e.g., the max block
> size they'll support... I'm not sure enhancing mtio would be the right
> solution here, since mtio has to work with IDE and FTAPE tape drives too
> (as much as we all wish 'ftape' would go away :-). Besides, the mtxl
> library works cross-platform, meaning that the utility would be useful
> for FreeBSD folks too (as well as folks on other maybe-supported
> platforms like SGI or Solaris, but I've never tested it there).
>
Enhancing mtio with some way to return the block size limits and other
information is possible but it should be done so that all tape drives
(IDE, SCSI, ftape, ...) can use the same mechanisms where applicable. One
way is to redefine MTIOCGET to contain more fields (I would like to see a
field somewhere for the partition number). Another possibility is to
define MTIOCGETDEV (or something like that) to return the "static"
information about the device and leave MTIOCGET for the "dynamic"
information.
If we define new ioctls for Linux, they end up being non-portable. Instead
of this we could as well define /proc entries for this kind of information
(this is in my list of things to do for 2.5).
The utility you propose may be a good solution because of its portability.
After all, it is not necessary to find out the tape drive capabilities
every day :-)
Kai
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