[RFC 2/2] ASoC: rt5670: Add LED trigger support

[Jaroslav Kysela]

Dne 24. 02. 21 v 12:43 Takashi Iwai napsal(a):

>>> So far, a user control is merely storing the value, let read/write via
>>> the control API.  That's all, and nothing wrong can happen just by
>>> that.  Now if it interacts with other subsystem...
>>>
>>> A more serious concern is rather the fragility of the setup; for
>>> enabling the mute LED control, you'd have to create a new user-space
>>> control, the function of the control has to be ignored by some
>>> application and some not, etc.  This has to be done on each machine
>>
>> You're using "ignore", but as I explained before, the user space switch will
>> be used in the whole chain:
>>
>> capture stream ->
>>   alsa-lib mute switch / silence PCM stream ->
>>   PA mute switch / silence PCM stream
>>
>> So PA can use this switch like the traditional hardware mute switch.
> 
> Does it mean PA would work as of now without any change?  Or does it
> need patching?

Yes, no PA modifications are required with my mechanism. The PA will just see
the new user space control - mute switch - created in alsa-lib - which will be
synced the internal PA path mute state like for the hardware mute switch. I
also think that handling LEDs independently (outside the upper layers like PA)
is more flexible.

					Jaroslav

-- 
Jaroslav Kysela <perex at perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.