Re: [PATCH] libata atapi work #2.1

[Pat LaVarre <p.lavarre@ieee.org>]

Jeff G:

> something is working...
 
Yes!

In my one sample, even misaligning a dd-shattered stream costs me only
0.5 GB/min at the outside of the disc, so command/ status overhead is
running reasonably low.

> Please let me know what patches (if any
> besides #define) are needed for setup, after
> you include patch #2.2 and #2.3 in the pile.

I will revert to -bk3 vanilla, then apply 2.* from linux-ide, then
report back.

> Two main things on the SCSI end of ATAPI to
> do:
> * issue REQUEST SENSE, to simulate an
> auto-sensing scsi device

I will try to create a desired inference of ATAPI op x03 "REQUEST SENSE"
to immediately follow the failing command, after the pattern of the
existing inference of ATA op xA1 "IDENTIFY".

I will have to discover how to auto sense only after a plain failure,
not inappropriately after a timeout.  Last I checked, the code was
written to see any failure as if it were a timeout.

> * in INQUIRY output, simulate compliance with
> MMC-3.  Linux SCSI stack is not aware that all
> ATAPI devices report zeroes in the SCSI version
> field (as do some USB storage devices).  So,
> we fake it.

I will try to munge the otherwise transparent pass thru of op x12
"INQUIRY" after the pattern of:

http://lxr.linux.no/source/drivers/usb/storage/protocol.c?v=2.6.5#L62

62 static void fix_inquiry_data(Scsi_Cmnd *srb)
...
82         /* Change the SCSI revision number */
83         databuf[2] = (databuf[2] & ~7) | 2;

I suppose there is no saving the transparency of ioctl CDROM_SEND_PACKET
and ioctl SG_IO.  Because of this linux-scsi legacy, we have to lose the
bits that we read from the device.

Pat LaVarre