Merge tag 'mute-led-rework' of https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound into asoc-5.13

ALSA: control - add generic LED API

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).

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

Link: https://lore.kernel.org/r/20210317172945.842280-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 20 insertions, 9 deletions

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 37179a8b1ceb..fa3719ef80e4 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -938,6 +938,9 @@ int software_node_register(const struct software_node *node)
 	if (software_node_to_swnode(node))
 		return -EEXIST;
 
+	if (node->parent && !parent)
+		return -EINVAL;
+
 	return PTR_ERR_OR_ZERO(swnode_register(node, parent, 0));
 }
 EXPORT_SYMBOL_GPL(software_node_register);
@@ -1002,25 +1005,33 @@ EXPORT_SYMBOL_GPL(fwnode_remove_software_node);
 /**
  * device_add_software_node - Assign software node to a device
  * @dev: The device the software node is meant for.
- * @swnode: The software node.
+ * @node: The software node.
  *
- * This function will register @swnode and make it the secondary firmware node
- * pointer of @dev. If @dev has no primary node, then @swnode will become the primary
- * node.
+ * This function will make @node the secondary firmware node pointer of @dev. If
+ * @dev has no primary node, then @node will become the primary node. The
+ * function will register @node automatically if it wasn't already registered.
  */
-int device_add_software_node(struct device *dev, const struct software_node *swnode)
+int device_add_software_node(struct device *dev, const struct software_node *node)
 {
+	struct swnode *swnode;
 	int ret;
 
 	/* Only one software node per device. */
 	if (dev_to_swnode(dev))
 		return -EBUSY;
 
-	ret = software_node_register(swnode);
-	if (ret)
-		return ret;
+	swnode = software_node_to_swnode(node);
+	if (swnode) {
+		kobject_get(&swnode->kobj);
+	} else {
+		ret = software_node_register(node);
+		if (ret)
+			return ret;
+
+		swnode = software_node_to_swnode(node);
+	}
 
-	set_secondary_fwnode(dev, software_node_fwnode(swnode));
+	set_secondary_fwnode(dev, &swnode->fwnode);
 
 	return 0;
 }