[UFO Chicago] IDE-CD / IDE-SCSI switching

[Sean Neakums]

Larry Garfield <larry at garfieldtech.com> writes:

> I had lilo.conf configured with the line
>
> append="hdc=ide-scsi"
>
> To tell it to use the scsi emulator for hdc.  When I removed that,
> however, and just let it figure it out on its own, it still used
> ide-scsi for hdc... but not for hda (the hard drive).  And then the
> above rmmod/insmod pair worked fine, and I now have burning and DVD
> support from the same drive.
>
> So yay, it works.  But can someone explain how it is that it knows how
> to use ide-scsi for just the one drive and not any others?

This is because ide-scsi is for ATAPI devices only and not for ATA
devices, which is what hard drives are.  (The ATAPI command set is
quite similar to the SCSI command set, whereas ATA is a different
kettle of fish entirely.)  The ide-scsi boot parameter is only useful
if you have both ide-cd and ide-scsi built statically.  In this
situation, absent the boot parameter, ide-cd will claim the CD/DVD
devices and ide-scsi won't get a look-in.  And as you've discovered,
if you leave the boot parameter in place in a modular ide-cd/ide-scsi
situation, when ide-cd is loaded it just ignores hdc, as it was
instructed.