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