using the openmoko neo101 in mass storage mode
joerg at openmoko.org
Wed Jun 4 15:25:03 CEST 2008
Am Mi 4. Juni 2008 schrieb Andy Green:
> Somebody in the thread at some point said:
> | On Fri, May 30, 2008 at 11:53:29AM -0700, Matt Mets wrote:
> |> I believe this has been discussed at some point, but there is a
> |> file-storage module that emulates a mass storage device:
> |> http://www.linux-usb.org/gadget/file_storage.html
> |> I don't see it included in the preview ASU package, but it should be
> |> trivial to build separately.
> |> The issue (that I see, anyway) is that it requires exclusive access to
> |> the drive that it uses for the storage.
> | I think we could get around with pretending to be a digital camera / media
> | player instead. IIRC the protocol prefered by windows for these is more
> | like a file server protocol (i.e. commands at file level) although maybe
> | windows doesn't allow to download files from media players and may not
> | allow to upload on cameras.
> | But that should get around the exclusive access problem.
> | Also there could be an image file which is shared via USB storage so no
> | need to unmount the SD card.
> That is true, Joerg also mentioned a separate partition which works as
> well. Each requires a fixed allocation of storage from the medium but
> it isn't death.
> The thing that bothers me is the effective requirement to force unmount
> the filesystem either way. It's for sure you wanted that filesystem
> mounted in the device when it isn't presented as mass storage gadget, so
> it limits you to scenarios where you never hold the files in there open
> long term. So media playing or camera kind of usage would be OK as we
> are familiar with from mp3 players as mass storage, but there are many
> other kinds of access that hold a handle open on the file long term, eg,
> database file. Especially when it's your /home that is getting shared,
> on a Linux box you might have a few painful bleeding stumps if you
> plugged it in and forced umount (which some folk anyway deliver by
> looking in lsof -n | grep mountpoint and killing everything).
> Another side of it is I use the GTA02 tethered by USB cable to a host
> for power and Ethernet-over-USB access, if I used the mass storage
> gadget as well then I would likely not want the modal behaviour that my
> storage filesystem is forced unmounted the whole while I am hooked to
> the host. I would transfer files and then want to do something with the
> files during a session.
> These objections don't really kill mass storage gadget as something to
> consider, but sharing a filesystem at the network layer just doesn't
> have these problems and acts like we are used to in normal Linux usage.
> ~ It's annoying that basically Windows will drive us to decide which way
> to jump or if to implement both, but there we are.
Sometimes it's quite inspiring to look to the ways others cope with the issue.
Nokia for instance is popping up a requester asking whether you want to have
mass storage profile or [fill in any conflicting mode here], then when you
select "mass storage device" it even disconnects GSM and blocks UI (I've been
told) - I'd guess they have the same kind of problems and solved them by
doing what we would call "init 1". And hey, we can do same - no?
Not cute, but very clean and simple. Probably when you want mass storage, you
have to live with solutions like this.
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