Why don't backends find hp on usb?

[Larry Evans]

On 10/28/2005 07:04 AM, Larry Evans wrote:
[snip]
> I've also read:
> 
>   http://localhost:631/spm.html#6_2
> 
> which contains:
> 
>   The serial backend lists devices by looking at serial port files
>   in the /dev directory
> 
[snip]
> indicates backends are in /usr/lib/cups/backend/, I looked there to
> find:
>[snip]
>  hp
>  http -> ipp
>  ipp -> ../backend-available/ipp
>  lpd -> ../backend-available/lpd
>  parallel -> ../backend-available/parallel
>  smb -> /usr/bin/smbspool
>  socket -> ../backend-available/socket
>  usb -> ../backend-available/usb
> 
> and since:
> 
>       <OPTION VALUE="hp:/no_device_found" >
> 
> appeared in the above HTML select element, I assume the
> above hp backend is simply a placeholder which should be

I assumed wrong.  Got following:

cd /usr/lib/cups/backend/
../hp
direct hp:/usb/PSC_2100_Series?serial=MY29BD553R0F "HP PSC_2100_Series" 
"hp:/usb/PSC_2100_Series?serial=MY29BD553R0F"

so the backend is finding the printer, but why is this choice not
provided to me when I trying modifying the hp printer?