dahdi: Do not define trace_printk if CONFIG_TRACING is not defined.

This was an accidental commit that slipped in as part of (a682401 "dahdi: Expose
dahdi devices in sysfs.")

Signed-off-by: Russ Meyerriecks <rmeyerriecks@digium.com>
Signed-off-by: Shaun Ruffell <sruffell@digium.com>
dahdi: Save the current maintstat in the span before calling into the drivers.

Some of the card callbacks needed maintstat set when processing loopup codes
from the remote side. This change is a modification of commit: (6c02c3c
"dahdi-base: Minor maint mode error")

Without this change cetain cards would not properly process the loopup /
loopdown codes (I know I should have more specific information here but the
details escape me at the moment).

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
oct612x: Break the oct612x out into a separate library.

Soon there will be more than one driver in the source tree that will want to use
these files. Compiling it as a library speeds the build since it won't have to
be built for each driver that wants to link it in.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Russ Meyerriecks <rmeyerriecks@digium.com>
wct4xxp: Companding on VPM needs to be changed when switching linemodes.

If a user switches linemode with sysfs, the VPM would never switch the
companding mode to alaw, and the result would be extreme static on all channels
of the span when the VPM is enabeld.

Now if the deflaw of the span has changed when an echocan is created, the
companding mode of the VPM channel is changed.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
dahdi: Prevent memory corruption on device unload.

The channels now have embedded 'struct devices' that contain a device_private
pointer in which to store the device private data. When a device is
unregistered in the system the device privata data is freed by the device core,
even though the chan_release function doesn't free the memory
associated with the device, So when dev_set_drvdata() is called,
it's writing into freed memory.

We also need zero out the embedded struct device before registration,
since we do not have any guarantee that it points to valid memory (or, if a
channel was unregisterd with sysfs, and then reregistered without being cleared
out).  Otherwise the core could try to use the previously freed private
data again.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Russ Meyerriecks <rmeyerriecks@digium.com>