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*                                                                           *
*                           TODO: BCM2835-AUDIO                             *
*                                                                           *
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1) Document the device tree node

The downstream tree(the tree that the driver was imported from) at
http://www.github.com/raspberrypi/linux uses this node:

audio: audio {
	compatible = "brcm,bcm2835-audio";
	brcm,pwm-channels = <8>;
};

Since the driver requires the use of VCHIQ, it may be useful to have a link
in the device tree to the VCHIQ driver.

2) Gracefully handle the case where VCHIQ is missing from the device tree or
it has not been initialized yet.

3) Review error handling and remove duplicate code.

4) Cleanup the logging mechanism.  The driver should probably be using the
standard kernel logging mechanisms such as dev_info, dev_dbg, and friends.

5) Fix the remaining checkpatch.pl errors and warnings.