On 10/06/2016 04:01 PM, Takashi Sakamoto wrote:
On Oct 5 2016 17:41, Arnaud Pouliquen wrote:
Thanks for the explanation. Here is my use case: I have a card with 3 output devices: hw:0,0 HDMI associated controls: numid=1,iface=PCM,name='ELD' numid=2,iface=PCM,name='IEC958 Playback Default' numid=3,iface=PCM,name='Freq.Adjustment' hw:0,1 DAC associated controls: numid=4,iface=PCM,name=' Freq Adjustment' hw:0,2 SPDIF associated controls: numid=5,iface=PCM,name='IEC958 Playback Default' numid=6,iface=PCM,name='Freq Adjustment'
My concern is to differentiate the controls associated to the outputs. Seems that it could be done using device field, but iecset is based on index (or i missed something?). Adding an option in iecset to address control by device could solve the issue... but it is to good way to handle the use case?
Complementary solution would be that control device field corresponds to PCM device, to allow to address PCM device with args (for instance AESx params for iec)
This is linked to the management of DAI PCM controls that has already been discussed in thread associated to this patch: http://www.spinics.net/lists/alsa-devel/msg47611.html. I can rework my patch (suppress iec generic control, to simplify it) but this only treat DAI controls not BE and "dai less" codecs.
Hm. In configuration space (namespace) of alsa-lib, the 'hw:0,1' PCM node is a short representation of 'pcm.hw:0,1,0'; each member expresses:
- pcm: interface
- hw: plugin name
- 0: card number
- 1: device number
- 0: subdevice number
Next, when identifying a control element, 'struct snd_ctl_elem_id' is used in ALSA control core. Layout of the structure is in <sound/asound.h>:
struct snd_ctl_elem_id { unsigned int numid; snd_ctl_elem_iface_t iface; unsigned int device; unsigned int subdevice; unsigned char name[44]; unsigned int index; };
Under the above design, when using a proper combination of iface/card/device/subdevice, we can represent the relationship between a control element and a PCM node.
But in a case of control elements for IEC 60958 type, we need to read this patch, commit ea9b43addc4d ("ALSA: hda - Fix broken workaround for HDMI/SPDIF conflicts"). http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/?id=ea9b4...
In this commit for former Intel HDA driver, two issues were addressed:
- multiple codecs gives functionalities of digital interface such as HDMI.
- bug of mixer interface in alsa-lib
not aware about alsa-lib issue... Have you an URI that details the issue?
Due to the issues, 'index' field is used, instead of the design I described.
Although, the requirement for HDA codecs (verb parser) and your requirement is different. I think it better for you to follow the above design, then fix the bug of mixer interface in alsa-lib. At least, via the other ctl-related APIs such as ctl/hctl, the control element can be selected and processed in user land.
First, sorry i think my mail is not Cristal clear
Let clarify the my devs:
1) My original implementation is here : http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/sound/soc/s... this does not work due to index that is overwritten Notice that my issue is not limited to iec958 control, but controls in generals
2) In parallel, I proposed generic code to implement: IEC control + possibility to attach DAI ctrl to PCM device:http://mailman.alsa-project.org/pipermail/alsa-devel/2016-March/105502.html
Right now, I propose to focus on point 1) that integrates constraints for DAIs and forget the patch-set that includes IEC generic control (if you interested in this code, i can rework it in a second step)
STI DAI driver uses DAI control interface. Index is forced to 0 but as device is also set, no error on ctrl registration. Handle index based on HDA codec implementation means I need to bypass DAI ctrl helpers... Should be nice to have a more generic way, as several implementations can face the same issue.
Perhaps this could be handled in a generic way in control.c? Today if control is identical, snd_ctl_add returns an error. Instead an auto-incrementation mechanism could be implemented to increase index.
This is linked to the management of DAI PCM controls that has already been discussed in thread associated to this patch: http://www.spinics.net/lists/alsa-devel/msg47611.html. I can rework my patch (suppress iec generic control, to simplify it) but this only treat DAI controls not BE and "dai less" codecs.
I can't follow all of messages in the related threads, but:
[alsa-devel] [PATCH v3 1/4] ALSA: pcm: add IEC958 channel status control helper http://mailman.alsa-project.org/pipermail/alsa-devel/2016-March/105152.html
Takashi Iwai wrote:
Hmm, this doesn't always work. It will create the substream_count ctls starting from the pcm dev# as index. What if there are 2 PCM devices where both contain 4 substreams?
struct snd_ctl_elem_id.subdevice can represent the index of PCM substream because current PCM core expresses the substreams as the subdevices. http://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/tree/sound/core/...
[alsa-devel] [PATCH v3 1/4] ALSA: pcm: add IEC958 channel status control helper http://mailman.alsa-project.org/pipermail/alsa-devel/2016-March/105158.html
Takashi Iwai wrote:
This pretty much depends on the hardware design. If each substream is really individual, you'd need to give the control for each substream.
I'll assist his advice for your issue.
For IEC generic ctrl, hope that this point has be integrated in V4: http://mailman.alsa-project.org/pipermail/alsa-devel/2016-March/105505.html index is no more overwritten by snd_pcm_create_iec958_ctl and subdevice is added in function params
Thanks and Regards Arnaud