On Wed, Feb 02, 2000 at 13:25:49 -0700, Drew Eckhardt wrote:
> In message <[EMAIL PROTECTED]>, [EMAIL PROTECTED] writes:
> >On Tue, Feb 01, 2000 at 22:40:26 -0700, Drew Eckhardt wrote:
> >> In the SCSI-1 spec that some of this conformed to, Read-6 was required.
> >> Read-10 was suggested as a good idea. Since some devices Wedged until
> >> power cycled when fed a command they didn't support, I figured that
> >> using Read-6 until we absolutely positively had to use Read-10 was a
> >> fine idea.
>
> >FWIW, even in the SCSI-1 spec, 10-byte reads were mandatory for CDROM and
> >WORM devices, and 6-byte reads were optional. (It is that way in the
> >SCSI-2 spec, and I think in the MMC specs as well.)
>
> I worked off the X3T9.2 REV 17B draft.
The above information is from that draft. :)
> It covers Direct Access devices, Sequential Access devices, and Printers.
It also covers CD (read only direct access) and WORM devices.
> In each section, there are tables of 6 and 10 byte supported commands. In
> the Direct Access section we have the following:
>
> Key: M = Command implementation is mandatory.
> E = Command implementation is required for SCSI devices that support
> device-independent self-configuring software.
>
> Table 8-1
> Group 0 Commands for Direct-Access Devices
>
> ==============================================================================
> Operation
> Code Type Command Name Section
> ------------------------------------------------------------------------------
> 08H M READ 8.1.4
> Table 8-22
> Group 1 Commands for Direct-Access Devices
> 28H E READ 8.2.2
Key: M = Command implementation is mandatory.
E = Command implementation is required for SCSI devices that support
device-independent self-configuring software.
O = Command implementation is optional.
R = Operation code is reserved for future standardization.
V = Operation code is available for vendor unique commands.
Table 13-1
Group 0 Commands for Read-Only Direct-Access Devices
==============================================================================
Operation
Code Type Command Name Section
------------------------------------------------------------------------------
[ ... ]
08H O READ 12.1.1
[ ... ]
Table 13-2
Group 1 Commands for Read-Only Direct-Access Devices
==============================================================================
Operation
Code Type Command Name Section
------------------------------------------------------------------------------
[ ... ]
28H M READ 12.2.1
[ ... ]
> >The way we handle this in FreeBSD is to specify a minimum command size in
> >the function that builds read and write CCBs.
>
> Under Linux, the CD and disk drivers are completely divorced. When I
> wrote the disk driver, I used the smallest command possible for a given
> transfer size. The CD driver was cloned from that.
>
> They should probably share a common direct-access support file that
> does that.
Ken
--
Kenneth Merry
[EMAIL PROTECTED]
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