RE: Linux USB Serial

["Steven J. Ackerman" <steve@acscontrol.com>]

Greg-

Thanks for your response.

Not sure if I need the cdc-acm functionality or not.

This is a color lcd display that supports a usb serial interface to
interact. I really 
just need to be able to send and receive characters and NAK the pipe back 
temporarily when my input buffer is full.

The descriptors were supplied by the chip vendor - Renesas - as part of a 
CDC demo application. The VID/PID is ours. The device works great under 
Windows XP with the descriptors as shown previously - even with the 
Communications bInterfaceSubClass value wrong.

Doing the modprobe, etc. was based upon some blog posts that purported
to show how to add support for an unknown usb serial device.

Looking at the descriptor for a FTDI USB serial to TTL cable it seems a lot
simpler,
but it does indicate vendor specific class, subclass and protocol - which
means 
that it requires a custom driver - ftdi_sio - right ?  I don't really want
to have to 
develop and support that.

I don't think that I have enough Linux experience to be able to test a patch

and rebuild of the kernel, and I don't think that I can ask my customers to
do 
that it order to use our product as a simple serial display.  

I'm running Ubuntu 10.10.

Any additional pointers and/or ideas would be greatly appreciated.

Thank you again,

Steven J. Ackerman, Consultant
ACS, Sarasota, FL
http://www.acscontrol.com
mailto:steve@acscontrol.com


> -----Original Message-----
> From: Greg KH [mailto:gregkh@linuxfoundation.org]
> Sent: Monday, September 17, 2012 5:42 PM
> To: Steven J. Ackerman
> Cc: 'Bjørn Mork'; linux-usb@vger.kernel.org; linux-serial@vger.kernel.org
> Subject: Re: Linux USB Serial
> 
> On Mon, Sep 17, 2012 at 05:07:26PM -0400, Steven J. Ackerman wrote:
> > Bjrn-
> >
> > Thank you for your response.
> >
> > This change gets me closer. I can now successfully execute the modprobe
> > without error, but the device still doesn't show up in /dev/ttyUSB? .
> >
> > sja@UBUNTU-10:~$ sudo modprobe usbserial vendor=0x0c6a
> product=0x0005
> 
> Eeek, no, never do that with a device you actually want to use.  This
> should be controlled by the cdc-acm driver, not the usbserial driver.
> That driver should be auto-loaded for this device, but it looks like the
> descriptor is wrong, so it's not binding to it.
> 
> Are you able to test a patch and rebuild the kernel to see if we can get
> this to work properly?
> 
> thanks,
> 
> greg k-h


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