[alsa-devel] [PATCH 1/4] dt-bindings: Document the dmas and dma-names properties for bcm2835-analog-audio

[Rob Herring]

On Mon, Mar 20, 2017 at 12:07 PM, Michael Zoran <mzoran at crowfest.net> wrote:
> On Mon, 2017-03-20 at 11:50 -0500, Rob Herring wrote:
>> On Sat, Mar 11, 2017 at 10:38:17PM -0800, Michael Zoran wrote:
>> > Add documentation for the DMA properties required when using the
>> > PWM controller of the bcm2835 for analog audio output.
>> >
>> > Signed-off-by: Michael Zoran <mzoran at crowfest.net>
>> > ---
>> >  Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt | 9
>> > ++++++++-
>> >  1 file changed, 8 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
>> > b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
>> > index cf573e85b11d..08fc06fc083a 100644
>> > --- a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
>> > +++ b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
>> > @@ -1,14 +1,21 @@
>> >  BCM2835 PWM controller (Raspberry Pi controller)
>> >
>> >  Required properties:
>> > -- compatible: should be "brcm,bcm2835-pwm"
>> > +- compatible: should be "brcm,bcm2835-pwm" or "brcm,bcm2835-
>> > analog-audio"
>>
>> Compatibles are not for selecting usage modes. You should describe
>> the
>> connection to the pwm that makes it an audio output rather than
>> change
>> the compatible.
>>
>
> Cool, that's good to know that someone let me know after all this time.

Well, there are more submitters than reviewers and maintainers and we
have travel and vacation (aka lives).

>  And please tell how if DT nodes are an exact documentation of the
> hardware how are virtualized DT nodes like firmware getting into the
> DTs?

DT is software's view of the hardware. Firmware provides interfaces to
the OS just like a h/w device does. And just like h/w devices, the
firmware is not discoverable and needs to be described. Originally, DT
was the firmware's interface to the OS with OpenFirmware.

Rob