SBC/SPC how to detect eject request?

Pat LaVarre p.lavarre at
Wed Aug 17 06:09:06 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* Pat LaVarre <p.lavarre at>
:)  Fun, isn't it?  PDT 05h DVD/CD has solved significantly more of the  
issues inherent in RMB than PDT 00h, if you ask me.  I've never seen a  
good PDT 00h answer to sharing the eject button between the host kernel  
software and the device firmware.

Some device vendors solve this with vendor-specific CDBs.  ATAPI/ ATA  
has its own Get Media Status ATA command.  Host vendor Microsoft  
proposed a PDT 00h SCSI media status notification that never went  
anywhere, so far as I know, i.e., no device or host implemented it.   
USB can connect the eject button as its own device ("interface") that  
shares power with the mass storage.

Mac and much of Linux by design needs no stinking eject button, as I  
imagine you know.  If there were a standard, then there'd be an app  
that said "please don't press that button", whenever you were so rude  
as to do so.

Often the designs for sharing don't make much room for the code on the  
other end of the cable.  The firmware keeps all control or the software  
takes all control.  Those approaches slow adoption, I think.

Pat LaVarre

P.S. Google doesn't yet immediately lead me directly to Microsoft's  
SCSI HDD work that I remember.  Instead I get vague mention:


Windows 95 also supports an eject mechanism for devices that support  
it, so that users can use software control to eject media from a device  
(for example, new floppy disk drives that support software-based media  


or mostly I'm drawn into ATAPI/ ATA HDD and DVD/CD SCSI work.



/// [DVD/CD] MMC Get Event Status Notification and Windows


/// 04-349r0 SPC-3 MMC-5 Merge ...



Troy Davidson tried to take the Media Status notifications one step  
further. Wants to know from and OS side, what we can do. Stemmed from  
the host point of view  "if you're not ready do I care? Also, can I  
lock the media. Wanted to get rid of polling ... and unit attention,  
and put it into the device. Under Win 98 the usability GUID feature  
were added that made life better for the user. Not polling, advanced  
guess of the device capabilities. Already used to talking with hard  
drives, now what is different. Capabilities or problems can happen on  
the fly. This was a way to identify what has happened or is happening  
to the host. Historical semantics, drive is spun down, get TUR, are you  
ready, or not ready? Each device was different. A Zip took very little  
time to spin up so it's ok, a Jaz took too long so it failed.


Pat LaVarre

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