Re: [PATCH 1/4] soc/sound: tegra_max98090: do not invert headphone jack

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 02/04/2016 12:05 PM, Jonathan Tinkham wrote:
> On 02/04/2016 09:36 AM, Stephen Warren wrote:
>> On 02/03/2016 10:30 PM, Jonathan Tinkham wrote:
>>> The headphone jack should not be inverted
>>
>> Have you tested this on Venice2 as well as Nyan? I'm pretty sure
>> Venice2 was tested when this driver was written, and whoever added
>> Nyan support to the kernel simply assumed it would work. As such, my
>> suspicion is that this series will break Venice2 even as it fixes Nyan.
>
> I have not tested this on Venice2, only on Nyan. That seems like a
> plausible cause and reasonable suspicion.
>
>> Why doesn't user-space expect what the kernel actually implements? The
>> kernel should be defining the control naming.
>>
>> Which user-space are you using specifically, and which part of it
>> expects particular naming?
>>
>> Perhaps this series needs to be parametrized based on a flag in DT,
>> rather than switching the hard-coded values, so that only Venice2 can
>> be affected?
>
> Specifically pulse-audio and alsa under Arch Linux.
>
> I was referencing 'Documentation/sound/alsa/soc/dapm.txt' with regards
> to control names. While it is possible to add another entry into the
> user-space configuration, I took this documentation as a definition of
> kernel control naming schemes, and thought the driver had used a
> non-standard naming scheme (or at least, not a consistent one).
>
>> On 02/03/2016 10:31 PM, Jonathan Tinkham wrote:
>>> Update device-tree bindings to reflect the rename of the board's
>>> headphone jack.
>>
>> This looks like an incompatible change to the DT. While you've fixed
>> the DT, which will fix new installations, old DTs now won't work. This
>> breaks DT ABI. Any DT change needs to be backwards compatible, i.e.
>> the old name should still work and be documented as a legacy value.
>
> I see that now. If the inversion behavior differs between venice2 and
> nyan, then another compatible string would need to be added anyways,
> correct? As you mentioned above, this might need to be done anyways for
> the rename.
>
> Something like:
> - "compatible = nvidia,tegra-audio-max98090" implements old inversion
> behavior and leaves the switch as "Headphones" to avoid breaking older DTs
> - "compatible = nvidia,tegra-{venice2,nyan}-audio-max98090" that
> separates the inversion behavior and also introduces the rename

It'd be preferable to key this off an separate flag rather than the 
compatible value. That would more directly represent the data in 
question, and allow any future boards to be added without having to edit 
the driver to know whether those new boards neded HP DET inversion or not.

However, do note that each of the 3 boards using this binding has a 
board-specific compatible value present already:

nvidia,tegra-audio-max98090-venice2
nvidia,tegra-audio-max98090-nyan-blaze
nvidia,tegra-audio-max98090-nyan-big
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