Re: Driver for Microsoft USB Fingerprint Reader

[Daniel Bonekeeper]

Maybe this is not a default on the market and is something that is
coming... but seems that some USB controllers are coming with DMA
capabilities:

http://www.usb.org/developers/presentations/pres0501/Augustin_DMA_Implem_Final.ppt
http://www.semiconductors.philips.com/pip/isp1183.html

Daniel

On 7/3/06, Greg KH <greg@xxxxxxxxx> wrote:
> On Mon, Jul 03, 2006 at 06:11:03PM -0400, Daniel Bonekeeper wrote:
> > >> Reading Greg's comment, now I'm in doubt if this should really be in
> > >> kernel mode or at userspace. Since there is no standard (AFAIK) for
> > >> those readers, how should it be done ?
> > >
> > >It all depends on what you want the userspace interface to be.
> > >
> >
> > That's one problem: I don't want to create one more userspace
> > interface for that. I suppose that all the hundreds of fingerprint
> > readers that ships with a SDK have their own way of doing that.. that
> > looks awfull to me, even though I believe that currently there isn't
> > any uniform way of working with fingerprint readers... shouldn't we
> > have a way to classify devices ? For example, if I want to list all
> > the printers connected via USB (supposing that we have more than one),
> > I should be able to request that information from somewhere
> > (/dev/usb/printers/* ?) I suppose that different fingerprint readers
> > works with different resolutions... we should be able to have an
> > unified interface that could tell the userspace the capabilities of
> > each fingerprint device (the area size of the scanner, resolution,
> > etc)... I think that applies for a lot of devices, not just
> > fingerprint readers. Probably there is already something like that.
>
> Yes, we should have one way of identifying them.  I've talked with Dan
> already about this in the past.  Please see his driver for support for a
> few devices already.
>
> > >> For example, I suppose that some (or all) USB devices may have DMA
> > >> capabilities... how is this done ?
> > >
> > >Heh, no, USB can't do DMA at all.  Why would you think they could?  It's
> > >a serial bus that just streams data across it at relativly slow speeds.
> > >
> >
> > Well.. even though I didn't know how and was a bit suspicious, I used
> > to believe that USB devices could do DMA because I heard some time ago
> > about "the danger of USB devices that could do DMA and have total
> > access over the OS"... something on bugtraq or securityfocus...
> > talking about USB and FireWire devices and how they could be used to
> > "inject" stuff on the system's memory and take it over... but I guess
> > it only applies to firewire (even though USB was clearly mentioned).
> > Reviewing it, it definitely applies just for firewire stuff.
> >
> > http://www.csoonline.com/read/050106/ipods.html
>
> Yes, firewire and USB is very different.  You can't dma memory directly
> out using USB, although I've heard rumors that through the USB debug
> port you might be able to do that, but as that requires a custom cable,
> which no one will give me, I can't confirm or deny that yet...
>
> thanks,
>
> greg k-h


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