[Stgt-devel] Prototype MMC DVD-ROM and burnable DVD+R implementation

[ronnie sahlberg]

Thanks for looking at this.

Your plan sounds great to me. Once implemented, Ill modify the mmc
emulation to hook into the new methods in
the template.

ronnie sahlberg



On Mon, Apr 21, 2008 at 4:03 PM, FUJITA Tomonori
<fujita.tomonori at lab.ntt.co.jp> wrote:
> Sorry for the delay.
>
>  On Tue, 15 Apr 2008 12:45:23 +1000
>
> "ronnie sahlberg" <ronniesahlberg at gmail.com> wrote:
>
>
>
> > On Tue, Apr 15, 2008 at 10:23 AM, FUJITA Tomonori
>  > <fujita.tomonori at lab.ntt.co.jp> wrote:
>  >
>  > >  Let me review the changes to the core first.
>  > >
>  > >  Once we agree on the changes to the core, please send them as separate
>  > >  patches. Then you can post mmc patches as you like, a single patch or
>  > >  multiple patches. I'm fine with either way.
>  >
>  > Great, thanks.
>  > Thinking about it, it might not be necessary to be able to create a
>  > LUN which lacks a backing store, so that part of my proposed patch
>  > it probably a mistake.
>  >
>  > The semantics in core and tgtadm that i think would be useful for
>  > devices such as MMC, and probably also SSC, that support
>  > removable/ejectable media would be
>  > 1, ability to administratively make LUNs online/offline. Such offline
>  > LUNs would still show up in report luns and be accessable, but the LUN
>  > when in offline
>  >     would behave as if there was no media loaded.
>  > 2, something similar to the two added lun methods :
>  > lu_online/lu_offline which are called when the online/offline
>  > attribute changes.
>  >    So that the lun emulation cna perform additional, commandset
>  > specific actions when the online attribute changes.
>  >    For MMC, I think online/offline would map very nicely to "media is
>  > inserted"/"no media loaded".
>  >    For MMC I think it would make sense to let the LUN close the
>  > backend file completely when the device goes offline and reopen it
>  > again
>  >    when the backend file goes online.   Thus
>  > offline/replacefile/online would be similar to eject tray/replace
>  > disk/close tray on a real physical device.
>  >
>  > I think that for SSC it would also make sense to have the emulation
>  > for this commandset also be informed/called on any/all changes on the
>  > online attribute
>  > in case SSC would want to map this and change its behaviour to map
>  > "tape is inserted"/"no tape loaded".
>  >
>  >
>  > Maybe there are better ways to implement this than lu_online/offline
>  > methods for the lun. Though, for removable media it would be nice if
>  > the offline/online cycle did close and reopen the backingstore file
>  > incase one wants to "swap the media" while the device is offline.
>
>  How about the following scheme?
>
>  - we add new hooks to device_type_template, online/offlne/reload.
>
>  - tgtadm can control the above methods.
>
>  - we let users to create a new logical unit without a backing-store
>  file. In this case, the logical unit is set to offline automatically.
>
>  - 'reload' method enables users to bind a new backing-store file to a
>  logical unit.
>
>  - 'reload' method works against only a offline logical unit (an online
>  logical unit could have outstanding commands and accept new commands).
>
>  - If offline logical units behaves as if there was no media loaded if
>  they are removable/ejectable media.
>