SDL_GetAudioDeviceSpec() not working properly with ALSA

[Harvie]

Hello, i am using SDL 2.30.0 to implement multiplatform audio capture. But i was surprised when one of the users reported it only works on pulseaudio and pipewire, but not on ALSA: sigrokproject/libsigrok#185

Reason is that SDL_GetAudioDeviceSpec() does not return correct values for ALSA capture device. Only way to get correct specs is by opening the device using SDL_OpenAudioDevice(). Therefore i had to implement following wrapper to get code working on ALSA:

int SDL_GetAudioDeviceSpec_open(int index, int iscapture, SDL_AudioSpec *spec)
{
	//ALSA does not allow to fully read specs of device without opening it.
	//This wrapper tries to open device when SDL_GetAudioDeviceSpec() incorrectly reports device to have 0 channels.
	//See https://github.com/libsdl-org/SDL/blob/237348c772b4ff0e758ace83f471dbf8570535e2/src/audio/alsa/SDL_alsa_audio.c#L759

	int ret = SDL_GetAudioDeviceSpec(index, iscapture, spec);
	if(!ret && spec->channels == 0) {
		printf("Failed SDL_GetAudioDeviceSpec(), trying to open device to get specs.");
		SDL_AudioDeviceID d;
		d = SDL_OpenAudioDevice(SDL_GetAudioDeviceName(index, iscapture), iscapture, spec, spec, SDL_AUDIO_ALLOW_ANY_CHANGE);
		if(d) SDL_CloseAudioDevice(d);
	}
	return ret;
}

But i think this is the exact thing that should be handled by SDL, because i use SDL exactly for the reason i don't want to care about any platform-specific hacks in my app. Can you please consider fixing this on SDL side?

Thanks