[RFC PATCH] sound: bcm2835-analog-audio: Add driver for bcm2835(Raspberry PI) headphone jack.

Michael Zoran mzoran at crowfest.net
Sun Mar 12 00:45:42 PST 2017

On Wed, 2017-03-08 at 14:27 -0800, Eric Anholt wrote:

> Make sure you use standard DT properties for describing the DMA
> channel,
> add your new compatible string to pwm-bcm2835.txt, and document that
> that compat string requires the DMA properties.

Hi Eric,

I submitted the audio driver, but what you are mentioning about using
pwm-bcm2835.txt has me thinking tonight.

Why couldn't the same device tree node be uses for both traditional PWM
and for Audio?  Why should the two be mutually exclude at load time? I
see nothing in the core APIs of either subsystem that prevents
either the same driver or the same tree of drivers from using the same
device tree node.

I read somewhere the purpose of the DT is to document HARDWARE NOT
DRIVERS.  I see no reason why a runtime interlock mechanism could be
used to that at runtime switches the mode of the drivers.  Open gnome-
music or pulseaudio, and it turns into a audio device. Open your custom
robot control software, and it becomes a simple PWM output.

Isn't this the same problem as using the GPU of the BCM2835 for either
a software radio or using it to do 3D graphics?

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