[issue1127] cdrom drive not detected

Matthew Dillon dillon at apollo.backplane.com
Thu Sep 17 08:38:01 PDT 2009

:I have a similar error on my home "debranded HP media PC" which is a 
:Core2Duo intel chipset based motherboard, SATA hard disk and DVDRW, with 
:bios option set to AHCI mode instead of IDE mode.  With default boot 
:options (no keyboard input) the CD fails to boot with same rootvp can't 
:be found, apparently trying acd0, which doesn't exist under AHCI, and 
:ends debugger prompt.  If I watch the boot process and choose the "no 
:AHCI" boot option, It finds the DVD rom and works fine, presumably 
:because acd0 exists under nata.  On a slightly older version, It would 
:fail to the mountroot prompt and typing in cd9660:cd0 works sometimes or 
:not with an "Device is in process of getting ready" type of message, 
:showing up...

    Hmm.  A CD/DVD detected via the AHCI driver will probe as 'cd0'.
    The root mount should try acd0, cd0, acd1, cd1, and cd8 (for USB
    attached CD/DVDs).

    The AHCI driver is supposed to probe everything before mountroot
    runs.  If it isn't one way to test and debug the situation is
    to type '?' + <return> at the mountroot> prompt several times.
    If the CD/DVD is still being probed then it should show up in the
    list after a few tries and you should then be able to specify it
    as the root mount.

    The question would then become: Why didn't it probe before the
    mountroot?  The AHCI driver explicitly probes devices before letting
    CAM finish up and mountroot to proceed.  To figure that out a verbose
    boot is probably needed.  Sometimes a verbose boot changes the timing
    enough such that the problem might not show up at all though :-(.


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