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. cheers jOERG
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