Re: Piggy-backing new hardware using old usb-serial

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On Wed, 2013-03-27 at 16:13 -0700, Greg KH wrote:
> On Wed, Mar 27, 2013 at 09:28:11PM +0100, Wesley W. Terpstra wrote:
> > On Wed, 2013-03-27 at 13:06 -0700, Greg KH wrote:
> > > > Our current prototypes borrow the Sierra VID
> > > And the USB-IF might revoke your vendor id, if they find you shipping a
> > > device with a different vendor id than the one you have been assigned.
> > 
> > One of the reasons we borrowed that VID is that we do not currently have
> > a VID assigned. We are still deciding whether it is worth joining the
> > USB-IF just to get a vendor ID for a few thousands of devices.
> > 
> > I am of the opinion that it is, but I cannot sign the membership forms
> > on behalf of GSI. We probably will end up buying a VID soon.
> > 
> > > Why not just add your device id to an existing driver, sending in a
> > > patch to do so.  All distros will pick that up and then your device will
> > > "just work" on all Linux distros.
> > 
> > I was under the impression that drivers in the linux mainline had to be
> > for hardware that was widely available.
> 
> Not true at all, we take drivers for _anything_ :)
> 
> > I take it then, that just adding support to an existing driver is
> > acceptable?
> 
> That's also ok, if you are using the same chip that the driver supports.
> 
> > That wouldn't address people with older linux distributions, but would
> > definitely be a good long term solution. It's really a shame there is no
> > USB-IF standard for usb-serial... then things would even potentially
> > work out of the box on windows.
> 
> You can use the CDC-ACM driver, as you have pointed out, which should
> allow your device to work on any OS with no driver needed, so maybe just
> use that instead.  There's no need to support modem commands in your
> device if you use it.

Greg's right, there's no reason not to use cdc-acm if you want to do
that, since not all cdc-acm devices are modems.  If you get a USBIF
vendor ID, then I'll happily add your device to the ModemManager probing
blacklist too.  That's kind of hard to do without a unique USB VID/PID
though :)

Dan

> > > > What driver should I target?
> > > What chip do you use for your device?
> > 
> > The device I am concerned about right now has an Altera arria2 connected
> > to a cy7c68013a-56baxc (fx2lp). We have several form factor variations.
> > A few have FTDI chips where I don't need to care, but can also do less.
> 
> If you use the ftdi chip, then use the ftdi driver, and add the device
> id that ftdi gives you to it.
> 
> Hope this helps,
> 
> greg k-h
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