kern/103602: drive gets wedged on READ CD CAPACITY if no disc is in

[Josh Carroll]

Thinking out of the box, I decided to use sg3_utils on both the
semi-working 7.0-CURRENT kernel I had, and on a Linux Knoppix 5.1 live
CD.

Pretty much every sg utility resulted in a acd0 FAILURE message (I ran
the commands against /dev/cd0 though of course). Here are the various
dmesg messages:

acd0: FAILURE - INQUIRY timed out
acd0: FAILURE - MODE_SENSE_BIG timed out
acd0: FAILURE - READ_CAPACITY timed out
acd0: FAILURE - SEND_KEY timed out
acd0: FAILURE - unknown CMD (0x46) timed out

It seems like every atapi command is timing out when I boot without a
disc in the drive. The only command that semi-worked was sg_turs.
Without a CD in the drive, I get the following output:

    test unit ready cdb: 00 00 00 00 00 00
test unit ready: Probably uninitialized data.
  Try to view as SCSI-1 non-extended sense:
  AdValid=0  Error class=0  Error code=0

 Raw sense data (in hex):
        00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
        00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00

If I insert a CD and run it, I get normal output (e.g. matching that
of what I saw on Knoppix):

    test unit ready cdb: 00 00 00 00 00 00

Perhaps there is a subtle difference with TUR with and without a disc,
which the kernel can sense and take appropriate action? When running
any of these sg* commands in Knoppix with no disc in the drive, I get
a message similar to this:

sg_readcap.no_disc.out:READ CAPACITY (10) failed, device not ready

Interestingly, the sg_vpd command fails to read the serial # as well,
so that is definitely a known bug with this drive I think. Here is the
sg_vpd output on Knoppix:

Supported VPD pages VPD page:
fetching VPD page failed

I don't know if the output of any of these sg commands on Knoppix is
useful (e.g. sg_get_config, sg_modes, sginfo) in terms of finding out
details of the device, but if interested I've posted a tarball of the
outputs here:

http://pflog.net/floyd/sg_output.tgz

Anyway, I thought some of this might be useful. At least I hope :)

Josh