cvs commit: src/sys/dev/ata atapi-cd.c atapi-cd.h

[Nate Lawson]

Søren Schmidt wrote:
> Scott Long wrote:
>> SXren Schmidt wrote:
>>> sos         2007-10-26 08:59:24 UTC
>>>
>>>   FreeBSD src repository
>>>
>>>   Modified files:
>>>     sys/dev/ata          atapi-cd.c atapi-cd.h   Log:
>>>   Update the way we get the mode pages on probe.
>>>     Revision  Changes    Path
>>>   1.194     +22 -25    src/sys/dev/ata/atapi-cd.c
>>>   1.47      +1 -0      src/sys/dev/ata/atapi-cd.h
>>
>> Just curious, what was the motivation for changing from doing a
>> TUR to doing a MODE_SENSE in g_access?  Your new code now relies
>> on what I'd consider is a fairly obscure feature of the SFF-8020i
>> spec, and one that contradicts the MMC and SPC specs that are now
>> used as the normative references for packet commands.  There's at
>> least once case, the virtual CDROM emulator in Parallels, that
>> appears not to support this feature, and I'd bet pretty heavily
>> that there are a number of real devices that won't support it
>> either.
>>
>> Without reverting to the old TUR code, an easy way forward is to
>> not fail the g_access command for the MST_FMT_NONE case.  This is
>> generally incorrect anyways as it just means that the device can't
>> specifically identify the media though it knows that the media is
>> inserted and valid.  Since this constant evaluates to 0x00, ignoring
>> it will also allow devices that don't support it to still work.  The
>> only side effect is that devices that don't support it will also not
>> be able to report MST_NO_DISC.  These devices will get handled later
>> as a side effect of reporting a bogus media size.
>>
>> Ultimately, I do think that the code needs to go back to using a TUR
>> and interpreting sense, asc, and ascq codes correctly.  The code prior
>> to 10/26 looks like it does this, so again I'm curious as to what ,
>> motivated the change.
>
> The code is only intended to work around the verbose error chatter from
> GEOM as it will read from a nonexisting media (if the drive is empty)
> during boot, and clutter the console needlessly. There is currently no
> way to prevent this, but I've talked to phk about it lately so this can
> be left out alltogether.
> Anyhow the only failure I've seen so far is Parallels when using a CD
> image as a virtual CDROM drive, it does a poor HW emu in that case if
> you ask me :)
> 
> Anyhow you are free to do what you want with the code until I get a real
> fix via GEOM done, but mind you the old code will not work on SATA ATAPI
> drives so a simple rollback of the commit is not really a fix...

While there may be a way to solve this automatically for ATA, this is
also an issue for floppy drives.  GEOM tries to read the floppy on boot
to see if there's a label, even if no media is present.  I think GEOM
should have a way of asking drives if they can tell if they have media
present and not probe them if they can't.  A separate env flag could be
set to say "always probe removable media" if users want the previous
behavior.  For most of us, this just causes boot delay.

-- 
Nate