Page 73 - Asterisk™: The Future of Telephony

Asterisk

chan_zap.so

/dev/zap
Linux kernel

Zaptel

Hardware driver
(wctdm)

Hardware

Figure 3-3. Layers of device interaction with Asterisk

Before compiling the Zaptel drivers on a system running a Linux 2.4
kernel, you should verify that /usr/src/ contains a symbolic link named
linux-2.4 pointing to your kernel source. If the symbolic link doesn’t
exist, you can create it with the following command (assuming you’ve
installed the source in /usr/src/):
# ln -s /usr/src/'uname -r' /usr/src/linux-2.4
Computers running Linux 2.6 kernel-based distributions do not usually
require the use of the symbolic link, as these distributions will search
for the kernel build directory automatically. However, if you’ve placed
the build directory in a nonstandard place (i.e., somewhere other
than /lib/modules/ <kernel version> /build/), you will require the use of
the symbolic link.
While Asterisk and the other related packages run on Linux 2.4.x ker-
nels, development is done first and foremost on 2.6.x kernels and
support for 2.4.x kernels is not guarenteed in the future.

The ztdummy Driver

In Asterisk, certain applications and features require a timing device in order to operate
(Asterisk won’t even compile them if no timing device is found). All Digium PCI hard-
ware provides a 1 kHz timing interface that satisfies this requirement. If you lack the
PCI hardware required to provide timing, the ztdummy driver can be used as a timing
device. On Linux 2.4 kernel-based distributions, ztdummy must use the clocking pro-
vided by the UHCI USB controller.

Compiling Zaptel | 45