[PATCH v2] ASoC: rt1316: Add RT1316 SDCA vendor-specific driver

[Pierre-Louis Bossart]

On 2/18/21 3:44 AM, Jaroslav Kysela wrote:
> Dne 18. 02. 21 v 10:12 shumingf at realtek.com napsal(a):
> 
>> +	SND_SOC_DAPM_SWITCH("DAC L", SND_SOC_NOPM, 0, 0, &rt1316_sto_dac_l),
>> +	SND_SOC_DAPM_SWITCH("DAC R", SND_SOC_NOPM, 0, 0, &rt1316_sto_dac_r),
> 
> Truly, I don't understand the reason to have a separate L/R switch when we can
> map this functionality to one stereo (multichannel) control.
> 
> It's an issue for all ASoC drivers. We should consider to be more strict for
> the new ones.

At the same time we have to recognize that the L/R notion only makes 
sense at the input to the amplifier. The amplifier may recombine 
channels to deal with orientation/posture or simply select a specific 
input, and drive different speakers (e.g. tweeter/woofer). Dac L and R 
are often an abuse of language when the system have multi-way speakers. 
Exhibit A for this is the TigerLake device with 2 RT1316 and 4 speakers. 
L/R don't make sense to describe amplifier outputs and speaker position.

There's also a difficult balance to be found between exposing all the 
capabilities of the device, and making integration and userspace 
simpler. I2C/IS2 and SoundWire devices tend to expose more controls than 
HDaudio ones, and that was driven by a desire to optimize as much as 
possible. Some devices are designed with limited number of controls, 
others provide hooks to tweak everything in the system by exposing 
literally have thousands of controls. I don't think we should pick and 
choose which controls we want to expose, that's the codec vendor's job 
IMHO (or the device class definition when standard and applicable)