Messages in this thread | | | Date | Wed, 17 Oct 2007 19:43:14 -0400 | From | Bill Davidsen <> | Subject | Re: What still uses the block layer? |
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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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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