On Wed, 17 Mar 2021 18:29:39 +0100, Jaroslav Kysela wrote:
This patchset tries to resolve the diversity in the audio LED control among the ALSA drivers. A new control layer registration is introduced which allows to run additional operations on top of the elementary ALSA sound controls.
A new control access group (three bits in the access flags) was introduced to carry the LED group information for the sound controls. The low-level sound drivers can just mark those controls using this access group. This information is not exported to the user space, but user space can manage the LED sound control associations through sysfs (last patch) per Mark's request. It makes things fully configurable in the kernel and user space (UCM).
The actual state ('route') evaluation is really easy (the minimal value check for all channels / controls / cards). If there's more complicated logic for a given hardware, the card driver may eventually export a new read-only sound control for the LED group and do the logic itself.
The new LED trigger control code is completely separated and possibly optional (there's no symbol dependency). The full code separation allows eventually to move this LED trigger control to the user space in future. Actually it replaces the already present functionality in the kernel space (HDA drivers) and allows a quick adoption for the recent hardware (ASoC codecs including SoundWire).
# lsmod | grep snd_ctl_led snd_ctl_led 24576 0
The sound driver implementation is really easy:
- call snd_ctl_led_request() when control LED layer should be automatically activated / it calls module_request("snd-ctl-led") on demand /
- mark all related kcontrols with SNDRV_CTL_ELEM_ACCESS_SPK_LED or SNDRV_CTL_ELEM_ACCESS_MIC_LED
v4 changes:
- the LED access flags are private to kernel now (no user space API change)
- fixes (kctl management, sysfs cleanup)
- add the sysfs LED marking kcontrol management
v3 changes:
- reorder the controls_rwsem use to fix the remaining mutex issue card->controls_rwsem <-> snd_ctl_layer_rwsem
v2 changes:
- fix the locking - remove the controls_rwsem read lock in the element get (the consistency is already protected with the global snd_ctl_led_mutex and possible partial value writes are catched with the next value change notification callback)
- rename state to brightness and show the brightness unsigned integer value instead the text on/off string (sync with the LED core routines)
- remove snd_ctl_led_hello() function (CI warning)
- make snd_ctl_led_get_by_access() function static (CI warning)
- move snd_ctl_layer_rwsem lock before the registraction callback call in snd_ctl_register_layer() - optimization
v1:
Original RFC:
Cc: Hans de Goede hdegoede@redhat.com
Jaroslav Kysela (6): ALSA: control - introduce snd_ctl_notify_one() helper ALSA: control - add layer registration routines ALSA: control - add generic LED trigger module as the new control layer ALSA: HDA - remove the custom implementation for the audio LED trigger ALSA: control - add sysfs support to the LED trigger module ALSA: led control - add sysfs kcontrol LED marking layer
As we seem agreeing with this approach, I merged this patch set as is now for 5.13. For the further development, let's put changes over there.
An immutable branch was created on top of the clean 5.12-rc5, and tagged as mute-led-rework, too.
Mark, please pull from there if you need to patch further ASoC changes that are relevant with the feature.
Thanks!
Takashi