[BRLTTY] Are USB product ids hard coded in BRLTTY

[Elias Oltmanns]

Nicolas Pitre <nico at cam.org> wrote:
> On Fri, 8 Jun 2007, Elias Oltmanns wrote:
>
>> Hi all,
>> 
>> because there is no serial port on my computer, I hlve to connect my
>> old Handytech Modular 40 by means of a prolific usb-serial converter.
>> Sadly, brltty doesn't find the braille device searching the usb bus,
>> regardless whether pl2303 (the kernel module for teh prolific
>> usb-serial converter) is loaded or not. Loading pl2303 and accessing
>> the braille device thgough the serial interface /dev/ttyUSB?, however,
>> works perfectly well.
>
> BRLTTY only looks for true USB braille displays directly.  If you use a 
> USB-to-serial adaptor (of which there are plenty different ones) then it 
> is really a serial braille display to BRLTTY.

Well, the Braille Star is definitely not a genuine USB device. In
fact, I had set up brltty to access it through the serial interface
provided by the ftdi_sio kernel module once. I can see, however, that
it can make sense to restrict the probing algorithm to those
converters that are known to be used in certain braille displays
provided you can rely on the producers sticking to those converters.

>
>> The reason why I'd like to use the usb interface
>> rather than the serial interface is that the braille device is not
>> guaranteed to show up as ttyUSB0 all the time due to race conditions
>> and similar issues. It works most of the time and if there really is
>> no way to use the usb interface of brltty in this case, a bit of
>> slightly more sophisticated udev scripting will very likely do the
>> job. Still, I thought I'd ask first.
>
> The udev approach is certainly the sane thing to do in that case.

Unfortunately, it doesn't seem to be too easy to do it neatly as well.
Anyway, for the time being I have to be satisfied with what I've got.

Regards,

Elias