Re: Problems accessing USB Mass Storage

Randy.Dunlap
2002-09-17T18:20:27Z

On Tue, 17 Sep 2002, Jonathan Corbet wrote:

| Don't know if this is helpful or not, but, based on my messing around with
| SmartMedia USB stuff...
|
| SmartMedia cards are weird in that they have a (seemingly) random amount of
| waste space at the beginning of the card. Your 8MB card, in particular,
| has nothing of interest in the first 25 sectors. Some cards have a
| reasonable partition table in the first sector, and some don't. Modern
| Windows systems (and cameras, of course) seem to be able to access the
| filesystem on the card without needing to see a partition table.
|
| A little while I posted a Lexar SmartMedia driver patch which hacked around
| this by substituting a fake partition table when the first sector was read.
| I'm not sure it's the right solution, though. A better way, perhaps, is a
| little user-space program which writes the appropriate partition table
| depending on the card capacity. Note that fdisk doesn't (easily) work for
| this purpose, since it wants partitions to start on cylinder boundaries.
|
| You might try just using dd to copy your card to disk with an offset of 25
| sectors, and see of you can mount the resulting image.
|
| Then again, the interface to some SmartMedia readers is vastly more
| complicated, as the sddr09 driver shows.

This is a bit like what we (JE, David Brownell, and I) saw at
the USB plugfest in 1999. We had a camera device that we
couldn't mount as a filesystem, but we could dd it.
When we did that and studied the dd-ed file, we could see a
FAT filesystem beginning after the first <N> blocks (but more than
25 sectors IIRC -- more like after 50-100 KB, or maybe even more).

--
~Randy
"Linux is not a research project. Never was, never will be."
-- Linus, 2002-09-02