Devices not supporting read-6....

[Jens Axboe]

On Sat, Jan 22 2000, H. Peter Anvin wrote:
> > I invite you to read drivers/cdrom.c and include/linux/cdrom.h.  The
> > CDROM_SEND_PACKET ioctl has been added to the interface during the 2.3.x
> > series, and allows you to send arbitrary packets to a low-level cdrom
> > driver that supports CDC_GENERIC_PACKET (i.e. ide and scsi).
> > 
> > /me thinks the uniform cdrom driver is very cool, but then I'm biased.
> > 
> 
> This seems like the wrong way of doing this.  This *definitely*
> shouldn't be CDROM-specific.

It was put in the CD-ROM subsystem, since it was designed to be
independent of the specific CD-ROM type (allow queueing of commands
to ATAPI devices and not through ide-scsi). The CDROM_SEND_PACKET
was just a natural extension of the generic_packet() hook added
for ATAPI and SCSI drives, which was originally added to provide
uniform support for DVD CSS on both types. Later it was extended
to cover audio commands as well.

I have been thinking about the earlier comment you made, the one
about providing ATAPI support through SCSI emulation purely like
Windows NT does (and other OS' too). Provide a nice packet layer
that doesn't differentiate between ATAPI and SCSI, commands
could be queued through SG or similar. This exact discussion
was raised on linux-scsi about a year ago, if I remember correctly.


-- 
*  Jens Axboe <axboe en suse.de>
*  Linux CD-ROM Maintainer
*  http://www.kernel.dk

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