Hi. Since linux-2.6.16-gentoo-r3 the "USB DSL modem support" doesn't work.... I type make menuconfig, go to the USB support part, select "DSL modem support" towards the end, but pressing enter won't open it....
You need to enable CONFIG_ATM first, found under the networking section
I just checked 2.6.15 with a default config and it does exactly the same.