Re: Stackable USB Driver

Thanks Alan.
My desire/need for a stackable driver is quite different from the typical
filesystem use that you describe. It is possible I'm going down the wrong
path.

Although Linux culture fully endorses modifying drivers, manufacturers don't
always embrace that idea, and re-hacking after the manufacturer distributes
revisions can get to be a drag.

My need is to monitor printer status conditions (not data itself) so that
agents (help desk) outside the box can be notified when preventive
intervention or replacement is required. In the Windows environment it is
possible to insert a "filter driver" into the driver stack so that all of
the status info can be monitored. I was looking for an analogous solution;
vfs seemed promising, but it is not applicable to USB printer drivers.

usbmon seems like it could be workable, but the kernel image is
pre-installed and locked down so that if usbmon is not included in the
standard distro, it won't be added later. 

Now I'm looking for alternatives, and wonder about user-mode drivers.

Thanks again
Vic


-----Original Message-----
From: Alan Stern [mailto:[email protected]] 
Sent: Sunday, September 09, 2007 7:38 PM
To: Victor L. DiCara
Cc: [email protected]
Subject: Re: [linux-usb-devel] Stackable USB Driver

On Sun, 9 Sep 2007, Victor L. DiCara wrote:

> Is there a means for stacking USB drivers, perhaps similar to stacking
> filesystem drivers?
> 
> I have a need to monitor the USB stream to/from a printer _without_
changing
> the printer driver code itself.

Other people have mentioned usbmon as the way to monitor a USB stream.
But this doesn't answer your questio about stacking USB drivers.  In 
fact, I don't fully understand that question.

When one stacks filesystem drivers, this generally means using a file 
in one filesystem as the block storage for a different filesystem, 
right?  So the analog with USB devices would be to use one USB device 
as the host for controlling other USB devices.  Is that what you meant?

Alan Stern




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