USB usages?(Ben)

Werner Almesberger werner at almesberger.net
Thu Jun 9 16:29:05 EDT 2011


Stefan Schmidt wrote:
> Using the usb storage gadget driver from the linux kernel will give
> you the functionality to emulate a usb storgae device to the host.

Okay, the block device export. I was afraid it would be that
one :)

> 3) The partitions must hold and filesystem that the host actually
> understands. Speak fat32 or such if you want to connect it everywhere.
> Thats quite a limitation if you want the same partition shared for
> rootfs and usb storage emulation.

Hmm, but can you have FAT32 on NAND with what's available in Linux
today ? Even with the UBI block layer, it doesn't look as if this
was something that would work out of the box:

http://thread.gmane.org/gmane.linux.drivers.mtd/30856
http://thread.gmane.org/gmane.linux.drivers.mtd/30833

By the way, an interesting experiment should be to make a program
that creates a virtual block device that represents a snapshot of
any VFS file system as, say, a block device containing FAT, and
that translates modifications made at the block level back into
VFS operations.

You still couldn't "share" things, concurrent access would be
risky, and the whole things would need a few heuristics, e.g., to
determine when to propagate a number of block changes to the VFS,
but it ought to greatly simply just this sort of application.

As far as I know, such a thing doesn't exist yet. Everybody just
does block-level sharing.

- Werner




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