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:
>
> 1) call snd_ctl_led_request() when control LED layer should be
> automatically activated
> / it calls module_request("snd-ctl-led") on demand /
> 2) 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
> - https://lore.kernel.org/alsa-devel/28fffebd-1ce9-7480-0f2f-ed8369abddf1@xxxxxxxx/
> 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:
> - https://lore.kernel.org/alsa-devel/20210211111400.1131020-1-perex@xxxxxxxx/
> Original RFC:
> - https://lore.kernel.org/alsa-devel/20210207201157.869972-1-perex@xxxxxxxx/
>
> Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
>
> 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
