[PATCH] ALSA: hda/realtek: Add quirk for Lenovo Ideapad S740

[Pierre-Louis Bossart]

>>>> I believe that this sequence contains I2C writes to amplifier chips. It would
>>>> be really helpful, if Realtek can provide more information for the I2C master
>>>> interface for their codecs (describe basic I2C I/O).
>>>
>>> The biggest problem is to figure what address/value pairs to write
>>> with I2C into the amplifiers, and here the catch is that those I2C/I2S
>>> amplifiers may or may not be sourced from Realtek, and it'd be
>>> difficult for Realtek to provide documentation on their competition,
>>> wouldn't it?
>>
>> Sure, that's another problem.  But currently it's not clear even how
>> to communicate via I2C/whatever to the underlying chip, as it's done
>> via the vendor-specific COEF verb.  At least this could be opened, I
>> hope.
> 
> The nice thing if we know the I2C master communication is that we can create
> I2C bus in the HDA driver and do run i2cdetect to detect the connected chips.
> Yes, it's partial information, but it's far more better than this unreadable
> coef implementation.

Ah yes, now I see the idea. Very interesting indeed. It would help quite 
a bit if we can detect the devices and then go back to the OEMs to ask 
"can you give us the commands for device #42". In the absence of 
information, it would help filter the sequences extracted with scripts.