Re: 2.7 block ramblings (was Re: DMA for ide-scsi?)

[Jeff Garzik <jgarzik@pobox.com>]

On Mon, Sep 15, 2003 at 09:34:45AM +0200, Jens Axboe wrote:
> On Sat, Sep 13 2003, Jeff Garzik wrote:
> > Oh, and I'm pondering the best way to deliver out-of-bang ATA taskfiles
> > and SCSI cdbs to a device.  (for the uninitiated, this is lower level
> > than block devices / cdrom devices / etc.)
> > 
> >  ... AF_BLOCK is not out of the question ;-)
> 
> Eh... I wont comment on that. I think we are way into Garzik lala land
> there :)
> 
> I'd prefer just keeping sg_io_hdr, but dumping sg. A fully fledged bsg
> (block sg) implementation. That way programs continue to work like
> before on ATAPI/SCSI, for ATA we can use it as a task file transport.

I don't propose dumping the ugly "submit cdb/taskfile" ioctls, but we do
need to deprecate them.  The ioctls are awful for throughput, async
queueing, and the like.  And of course in general, ioctls are evil :)

And we should deprecate them with a solution that aligns what with Linus
described in Dec 2001 on lkml:  a chrdev where userland write(2)s cdbs
and taskfiles, and read(2)s the results.  This is where my thinking
picked up:  if we are creating a chrdev to send "packets" and receive
responses to those packets............  <insert conclusion here>

	Jeff