Re: libata: CD and dvd devices not recognized

[Albert Lee <albertcc@tw.ibm.com>]

Sergei Shtylyov wrote:
> Hello.
> 
> Albert Lee wrote:
> 
>> Thanks for the detailed log.
>> It looks like the bad INQUIRY command
>>   "CDB (4:0,1,0) 12 01 00 00 fe 00 00 00 00" (INQUIRY, length=254,
>> EVPD=1)
>> is coming from the user space, not the SCSI mid-layer.
> 
> 
>> I guess two problems together caused this bug:
>> 1. Ubuntu Linux issues an incorrect INQUIRY command to the drive.
>>    (Other distros seem to have the INQUIRY correct.)
> 
> 
>    But what is incorrect about sending INQUIRY with EVPD bit?

Nothing wrong from the SCSI point of view.
However, in the early ATAPI spec (sff-8020i), this EVPD bit is
"reserved". And apprently some imperfect ATAPI CD-ROM drive doesn't
handle it well when EVPD = 1. :(

Hmm, how about the revised version:
1. Ubuntu Linux issues a correct INQUIRY command to the drive
   which set EVPD = 1. However, EVPD is "reserved" per early ATAPI
   spec and the AOpen 56X/AKH drive times out in this case.
   ...

--
albert