[PATCH 0/2] alsa-lib: -ENODATA documentation
Hello all,
here's patch to document -ENODATA error as a PCM error code. We have recently merged patches to SOF firmware to use this error code: https://github.com/thesofproject/sof/pull/2918
Some additional background on the use-case: https://github.com/thesofproject/sof/issues/2564
In thread "Functionality of pcm_notify in snd-aloop?" https://mailman.alsa-project.org/pipermail/alsa-devel/2020-April/166974.html
.. we discussed the possibility for ALSA to provide a mechanism for application to wait for the condition to change, but at least for the currently known usages, the synchronization responsibility will be in user-space (UCM file will describe the PCM dependencies). Anyways, this is orthogonal to documenting -ENODATA, so sending this now.
Kai Vehmanen (2): pcm: add documentation for -ENODATA error code pcm: fix spelling in documentation for -EBADFD
src/pcm/pcm.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
This error code can be used e.g. with echo reference PCM devices (the SND_USE_CASE_MOD_ECHO_REF UCM token).
Signed-off-by: Kai Vehmanen kai.vehmanen@linux.intel.com --- src/pcm/pcm.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c index 1064044c9812..488a8dd0493d 100644 --- a/src/pcm/pcm.c +++ b/src/pcm/pcm.c @@ -292,6 +292,14 @@ This error can happen when device is physically removed (for example some hotplug devices like USB or PCMCIA, CardBus or ExpressCard can be removed on the fly).
+\par -ENODATA + +This error can happen if the device data transfer is dependent on +an external condition and that condition is not met. For example, +PCM device for echo reference as described by SND_USE_CASE_MOD_ECHO_REF +UCM token, may return -ENODATA if the linked playback stream has not been +started. + \section pcm_params Managing parameters
The ALSA PCM device uses two groups of PCM related parameters. The hardware
Signed-off-by: Kai Vehmanen kai.vehmanen@linux.intel.com --- src/pcm/pcm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c index 488a8dd0493d..79322b4eab0d 100644 --- a/src/pcm/pcm.c +++ b/src/pcm/pcm.c @@ -284,7 +284,7 @@ supports resume and the snd_pcm_prepare() call can be ommited. \par -EBADFD
This error means that the device is in a bad state. It means that -the handskahe between application and alsa-lib is corrupted. +the handshake between application and alsa-lib is corrupted.
\par -ENOTTY, -ENODEV
Dne 29. 05. 20 v 14:28 Kai Vehmanen napsal(a):
Hello all,
here's patch to document -ENODATA error as a PCM error code. We have recently merged patches to SOF firmware to use this error code: https://github.com/thesofproject/sof/pull/2918
Some additional background on the use-case: https://github.com/thesofproject/sof/issues/2564
In thread "Functionality of pcm_notify in snd-aloop?" https://mailman.alsa-project.org/pipermail/alsa-devel/2020-April/166974.html
.. we discussed the possibility for ALSA to provide a mechanism for application to wait for the condition to change, but at least for the currently known usages, the synchronization responsibility will be in user-space (UCM file will describe the PCM dependencies). Anyways, this is orthogonal to documenting -ENODATA, so sending this now.
Kai Vehmanen (2): pcm: add documentation for -ENODATA error code pcm: fix spelling in documentation for -EBADFD
src/pcm/pcm.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
I applied those two patches, and added a short description that there is no recovery mechanism and an event mechanism to notify the link availability at the moment.
https://github.com/alsa-project/alsa-lib/commit/f3597737defe495f9c618b12507c...
Jaroslav
participants (2)
-
Jaroslav Kysela -
Kai Vehmanen