Dne 24. 02. 21 v 9:52 Takashi Iwai napsal(a): > On Wed, 24 Feb 2021 09:14:41 +0100, > Jaroslav Kysela wrote: >> >> Dne 24. 02. 21 v 8:12 Takashi Iwai napsal(a): >>> On Tue, 23 Feb 2021 21:56:16 +0100, >>> Jaroslav Kysela wrote: >>>> >>>> Dne 23. 02. 21 v 17:20 Takashi Iwai napsal(a): >>>>>>> Of course, this implementation would make the integration much easier, >>>>>>> and that's a big benefit. So I have a mixed feeling and not decided >>>>>>> yet whether we should go for it right now... >>>>>> >>>>>> I think that we can reconsider the LED handling implementation later, when >>>>>> someone brings something better on the table. >>>>> >>>>> What worried me is the plan to expose this capability to user-space. >>>>> If it's only a kernel-internal, we can fix it in the kernel and >>>>> nothing else broken, but if it's a part of API, that's not easy. >>>>> >>>>> So, if any, I'd like to avoid exposing to the user-space at first. >>>>> (But then it comes to the question how to deal with a case like AMD >>>>> ACP...) >>>> >>>> I tried to propose a complete solution and the ACP was one strong reason for >>>> this kernel / user space API. So without the user space support, it's just >>>> a half solution for known issues. >>>> >>>> Frankly, I don't see any drawback or a problem even if we remove this API >>>> later. >>> >>> Removing the user-space API is absolutely no-go. The only exception >>> would be either the case really no one uses it or it's too buggy and >>> unfixable. >> >> This is a special case. Even if those LED bits are ignored by kernel in >> future, we expect to be replaced with another layer. Thus the functionality >> must be retained. > > Well, we cannot know whether the replacement really happens or > happened, and hence we never kill the old one. That's the problem. > >>>> The LED group bits are just informal for the user space and it's >>>> expected to create the user controls tied to this LED functionality only in >>>> alsa-lib/plugins at the moment. The kernel may return an error when the user >>>> space tries to set those new bits when the API is deprecated and I believe >>>> that the hardware design faults like AMD ACP (without the hardware mute) are rare. >>> >>> The experience tells us that users are creative enough to (ab)use a >>> new ABI in any unexpected ways, and we have no control for it. So >>> it's not about how alsa-lib is implemented but rather how ABI could be >>> abused :) >> >> Ok, I don't have other ideas. I don't agree with your argumentation for this >> particular case, where the functionality is marginal. Ideally, the AMD driver >> may be recoded to use double-buffering and software mute switch, so we should >> handle everything in the kernel space. > > My argument is that we're trying to add too much freedom just for this > "marginal" problem. Honestly speaking, I would feel rather more > comfortable if it were a kernel control element that just does trigger > the LED like the original patch from AMD guys. Then you cannot do > much wrong. OTOH, creating a virtual capture switch and let alsa-lib > handling the software mute, while PA should ignores the soft-mute but We can force the softvol even if PA set the skip flag for this particular PCM stream. > dealing only with the assigned mute LED... Sounds too complex to me. It seems that you misunderstood the number of issues which my code is trying to resolve: 1) set LED based on state from multiple cards (so you cannot trigger LED inside single driver / single control element); we need one arbiter; this is the main argument 2) unifies the audio LED interface 3) reduce the hardware driver code Jaroslav -- Jaroslav Kysela <perex@xxxxxxxx> Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
