Hi,
Some of us at Intel are confused with multiple definitions of
capture/playback dailink flags (credits to Rander Wang for reporting
this in https://github.com/thesofproject/linux/pull/2070).
struct snd_soc_dai_link {
[...]
/* For unidirectional dai links */
unsigned int playback_only:1;
unsigned int capture_only:1;
[...]
/* DPCM capture and Playback support */
unsigned int dpcm_capture:1;
unsigned int dpcm_playback:1;
[...]
};
And of course when you start looking at some machine drivers, there are
confusions, e.g. below with DPCM front-ends using one or the other set,
and with copy-paste and partial diffs, this propagates without being
consistent or being noticed:
[GLK_DPCM_AUDIO_HS_PB] = {
.name = "Glk Audio Headset Playback",
.stream_name = "Headset Audio",
.dpcm_playback = 1, <<<<
.nonatomic = 1,
.dynamic = 1,
SND_SOC_DAILINK_REG(system2, dummy, platform),
},
[GLK_DPCM_AUDIO_ECHO_REF_CP] = {
.name = "Glk Audio Echo Reference cap",
.stream_name = "Echoreference Capture",
.init = NULL,
.capture_only = 1, <<<< should this be .dpcm_capture = 1?
.nonatomic = 1,
.dynamic = 1,
SND_SOC_DAILINK_REG(echoref, dummy, platform),
},
[GLK_DPCM_AUDIO_REF_CP] = {
.name = "Glk Audio Reference cap",
.stream_name = "Refcap",
.init = NULL,
.dpcm_capture = 1, <<<<
.nonatomic = 1,
.dynamic = 1,
.ops = &geminilake_refcap_ops,
SND_SOC_DAILINK_REG(reference, dummy, platform),
},
So here are the questions:
- when using DPCM, is there an expectation to use dpcm_ flags only?
- should we instead use playback/capture_only when only one of the two
dpcm_ flags is set?
- should we flags errors if we ever encounter cases with e.g.
dpcm_playback = true and capture_only = true?
- do we actually need two sets of definitions? There are very few users
of the .playback_only and .capture_only flags and only a single place
where it's checked in soc-pcm.c
Thanks for your feedback
-Pierre
