Re: [Barry-devel] USB Research

[Chris F. <cd...@fo...>]

On Tue, Nov 13, 2007 at 09:46:45PM -0500, Martin Owens wrote:
> Hey Chris, Barry watchers,
> 
> I'm looking into the whole barry thing with respect to the udev/hal
> and it appears looking at udevmonitor program that the usb mass
> storage device driver is only taking one of the usb end points and it
> is leaving two of the end points free.

The problem as I understand it, and as I understand how USB works,
is that each device has 1 or more Configurations available.  In order
to talk to the device, the chosen Configuration is selected by
the host.

In the case of Barry vs. usb_storage, each needs a different
Configuration.  Barry uses the proprietary class 255 Configuration,
while usb_storage uses class 8 Mass Storage.

I don't believe it is possible to use two USB Configurations at once,
but if it is, I'd be happy to be proven wrong. :-)


> I'm wondering if there is a way to code parts of the barry driver to
> be kernel based to be called up by udev and claim some of these end
> points without having to change the mode to single mode.

It's certainly possible to have a kernel driver involved, but the underlying
USB architecture still needs to be dealt with, and there is a high
chance that the kernel driver would spend most of its time jumping
back and forth between Configurations.  And if the devices loses its
state in one Configuration when switching to another, that would slow
down both Mass Storage access and Database access.

Of course, if the filesystem isn't mounted, there's no reason both
Configurations have to be active at once.  I find your other email
regarding claiming the interface interesting in this respect.


> P.S. looking for im,  irc or other method for barry chatting.

I'm sometimes on irc.freenode.net.  I've setup #Barry just now.
I often find that irc conversations pass me by, since I can't be in
channel all the time.  Email is still the best way to reach me,
but irc is available.

- Chris