[LinuxPPS] LinuxPPS and multiple GPIO sources

[pete]

First, thank you all for your great work. I've really appreciated this 
work and have found it to be very useful and of high quality. 
Unfortunately I was unable to solve a problem with the existing docs, 
and am hoping I can find some direction here on the mailing list.  What 
I'm trying to do is connect two pps sources to a raspberry pi via two 
GPIO pins, say pin 25 and 18. I've got the first one working, but I 
can't seem to figure out the syntax for the kernel command line 
arguments. Does anyone have a suggestion?