Am 07.11.2011 14:36, schrieb Paolo Bonzini: > On 11/07/2011 02:21 PM, Markus Armbruster wrote: >> The commit message should explain why we need this callback. The cover >> letter says "support for eject requests is required by udev 173." >> Please elaborate on that. > > Well, first and foremost eject requests are in the spec. :) The fact > that recent guests need it is more a justification for pulling this in 1.0. > >> You implement it for IDE in PATCH 7/8 and SCSI in PATCH 8/8. You don't >> implement it for floppy, despite the comment. That's okay; floppy has >> no use for it. It's the comment that needs fixing. Devices that >> implement is_medium_locked() must implement this one as well. > > Right. > >> 1. eject without -f behaves like the physical tray button. It has >> immediate effect, unless the tray is locked closed. Then, the drive >> just notifies the OS of the button push, so the OS can react to it. The >> latter isn't implemented in QEMU. >> >> 2. eject with -f behaves like whatever physical way there is to pry the >> tray open, locked or not. CD-ROM drives commonly have a little button >> hidden in some hope you can reach with a bent paperclip. >> >> Could you explain your mental model? > > 1. eject without -f is as you mentioned. > > 2. eject with -f should really never be needed, but it does whatever is > needed to be able to follow up with a "change" command. It turns out it > is really "unlock" and "ask the guest to eject" combined, but that's the > implementation, not the model.
Does this give different results than just asking the guest to eject without forcefully unlocking? I would expect that a guest that responds to the eject request would also unlock the drive. In which case I think eject without -f should be enough? > The difference from the paperclip model is that it gives a chance for > the OS to clean up and eject safely. It wouldn't be hard to convince me > otherwise though, especially if it can help getting the patch in 1.0. > The "eject -f"+"change" can be replaced by "eject", possibly followed by > "eject -f" after a timeout, and then followed again by "change". Kevin
