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SubjectRe: What still uses the block layer?
Jeff Garzik wrote:

>> But again, please remember that these USB devices are really SCSI
>> devices. Same for SATA devices. There is a reason they are using the
>> SCSI layer, and it isn't just because the developers felt like it :)
>
> /somewhat/ true I'm afraid: libata uses the SCSI layer for ATAPI
> devices because they are essentially bridges to SCSI devices. It uses
> the SCSI layer for ATA devices because the SCSI layer provided a huge
> amount of infrastructure that would need to have been otherwise
> duplicated, /then/ massaged into coordinating between <jgarzik's ATA
> layer> and <SCSI layer> when dealing with ATAPI.
>
> There is also a detail that was of /huge/ value when introducing a new
> device class: distro installers automatically work, if you use SCSI. If
> you use a new block device type, that behaves differently from other
> types and is on a different major, you have to poke the distros into
> action or do it yourself.
>
> IOW, it was the high Just Works(tm) value of the SCSI layer when it came
> to ATA (not ATAPI) devices.
>
> For the future, ATA will eventually be more independent (though the SCSI
> simulator will be available as an option, for compat), but the value is
> big enough to put that task on the back-burner.
>
I remember being told that I didn't understand the problem when I
suggested using ide-scsi for everything and just hiding the transport. I
get great pleasure from having been (mostly) right on that one. I still
have old systems running ZIP drives as scsi...

--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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