[asterisk-dev] proper way to signal user information layer 1 (ISDN)

[Klaus Darilion]

Hi!

In case of digital ISDN calls I want to signal the ISDN user information 
layer 1 values between the dialplan (and maybe some apps) and the ISDN 
channel driver.

I see two ways of doing this:

1. an ast_variable (a global one with _ prefix so that it gets copied 
automatically) which is read/written by the ISDN channel drivers and the 
apps.

2. Adding ast_channel.userinformationlayer1. The channel driver and apps 
can access the value directly and from dialplan this can be done by 
enhancing func_channel.c (http://bugs.digium.com/view.php?id=10217)

This value exists only in ISDN, thus I'm not sure if a new member to 
ast_call is the proper way - but ISDN transfer capability is similar and 
this is already added to ast_chan.

thanks
klaus