On Sun, 30 Sep 2012, Aaron Lu wrote:

Makes sense to me, but there is a problem if I want to block events
checking for the disk, as I do not have a pointer to the gendisk in ATA
layer.

The tray will be ejected by the ODD itself when it has power, I do not
need to do that. Moreover, I don't think I need enable the GPE bit when
it has power.

It sounds like you need to add only two things to the sr layer: An 
interface to enable/disable event checking and an interface to request 
an eject.  (And perhaps ejects can be carried out entirely within the 
ATAPI layer, with no need to involve sr.)

Alan Stern