[RFC] Tape driver rationalization for Linux 2.5?

[RFC] Tape driver rationalization for Linux 2.5?

[Willem Riede]

Folks,

Being the maintainer of the driver for Onstream tape drives (osst) and
wanting to stay abreast with the kernel evolution, I've been reading up on 
some of the changes that are being made to the scsi sub-system in the 2.5.x 
kernel series, and that has got me thinking...

I've never really understood why there are separate high level drivers for
tape drives -- or cdroms for that matter (other than "it just happened that
way").

Also, I find the fact that the user needs to tell the kernel at boot time
whether (s)he is going to use ide-scsi or not awkward. You should be able
to point any appropriate driver to a device by loading the corresponding
module (and maybe tell the module specifically not to touch some compatible
device, but preferably just gracefully shared and locked (think sg)).

I'm not alone here, quoting Linus from the Scheduler thread:
   'And even more important than performance is being able to read and write
   to CD-RW disks without having to know about things like "ide-scsi" etc,
   and do it sanely over different bus architectures etc.'

Case in point for osst -- it handles IDE (DI-x0), SCSI (SC-x0), USB (USBx0)
and (not quite, but soon) Firewire (FW-x0) drives (it could in theory support
parallel port drives too given the right mid-level driver). So here you have 
a universal high level driver for a certain device type, usable regardless 
of the actual physical interface you use on your PC.

Yet there is ide-tape, which drives (only) DI-x0's too (but it is out of date).
Too often I read complaints on l-k about ide-tape. It is very complex, with
the pipeline, which I believe at today's PC performance has no added value.

The same tension exists between st and ide-tape. Why shouldn't st be the 
driver of choice for each and every QIC-157 compliant drive? (QIC-157 is a 
standard for a common SCSI/ATAPI command set for streaming tape, which in
turn is a subset of the SCSI standard for sequential access devices; 
I believe that's what st supports).

Ide-scsi -- which I feel should be renamed the "atapi" driver needs to be
enhanced to use Atapi Overlap and/or DSC on drives that support it, and then
st and ide-tape minus Onstream support and cdrom-c and sr.c (anything else?)
can be merged... No more ide-tape -- less bloat. (I admit to not knowing 
enough about cdrom drivers to know if the strategy would work there).

What do people think? 

Thanks, Willem Riede.

Re: [RFC] Tape driver rationalization for Linux 2.5?

[Nicholas Knight]

On Wednesday 19 December 2001 02:29 pm, Willem Riede wrote:
> Folks,
>
> Being the maintainer of the driver for Onstream tape drives (osst)
> and wanting to stay abreast with the kernel evolution, I've been
> reading up on some of the changes that are being made to the scsi
> sub-system in the 2.5.x kernel series, and that has got me
> thinking...
>
> I've never really understood why there are separate high level
> drivers for tape drives -- or cdroms for that matter (other than "it
> just happened that way").
>
> Also, I find the fact that the user needs to tell the kernel at boot
> time whether (s)he is going to use ide-scsi or not awkward. You
> should be able to point any appropriate driver to a device by loading
> the corresponding module (and maybe tell the module specifically not
> to touch some compatible device, but preferably just gracefully
> shared and locked (think sg)).
>
> I'm not alone here, quoting Linus from the Scheduler thread:
>    'And even more important than performance is being able to read
> and write to CD-RW disks without having to know about things like
> "ide-scsi" etc, and do it sanely over different bus architectures
> etc.'


Am I alone in knowing that, at least as of 2.4.9 (the earliest I'm 
really sure I used it on) through 2.4.16, you DON'T need any weird 
boot-time switches?
Simply DO NOT compile in the IDE CD-ROM drive, compile in SCSI CD-ROM 
and SCSI Generic support, and voila, fully functional ATAPI CD writer
this even works on my IDE DVD drive
to read from em, I just use /dev/scd#
I am using NO boot time flags, including ide-scsi