Re: [PATCH 2.6.20-rc3] fix broken retval test in sr_block_ioctl

[Jeff Garzik <jgarzik@pobox.com>]

Mark Lord wrote:
> This patch adds support for passing ATA_12 and ATA_16 commands
> through to ATAPI devices in libata.  In practice, the upper layers will
> still currently prevent ATA_16 commands, as no (?) ATAPI drives support
> them yet.  But it will work if such a drive is ever encountered.
> 
> This patch is necessary for using SG_IO from userspace,
> and an upcoming hdparm release will be updated to use this interface.
> 
> Signed-off-by:  Mark Lord <mlord@pobox.com>
> ---
> Allow ATA_12 / ATA_16 passthru commands to be issued for ATAPI devices

Douglas Gilbert noticed this a while ago.

The patch's technical content is fine, but there is an open policy 
question:  For some devices, there is an opcode overlap (BLANK?  Doug 
probably remembers the issue better than I).  And from a practical 
standpoint, to handle any vendor weird-isms (nahhh those never happen in 
ATAPI), it would be nice to be able to force the current (pre-mlord 
patch) behavior to ensure that all opcodes are passed to ATAPI.

Absent a better idea, I would simply suggest adding a module parameter 
that restores the "all opcodes are passed to device, guaranteed" mode.

I'm fine with changing the default behavior to that which is presented 
by your patch.

	Jeff