staging: greybus: audio: Add helper APIs for dynamic audio modules

Greybus Codec driver allows modules to be dynamically added and removed,
which further requires updating the DAPM configurations as well.

With current snd_soc architecture, dynamic audio modules is not yet
supported. This patch provides helper APIs to update DAPM configurations
in response to modules which are dynamically added or removed. The
source is primarily based on snd_dapm.c

Signed-off-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/35e1baaae10a3f2162e71be4c2f75a701584f0e6.1594290158.git.vaibhav.sr@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/greybus/Makefile

@@ -28,7 +28,7 @@ obj-$(CONFIG_GREYBUS_VIBRATOR)	+= gb-vibrator.o
 
 # Greybus Audio is a bunch of modules
 gb-audio-module-y	:= audio_module.o audio_topology.o
-gb-audio-codec-y	:= audio_codec.o
+gb-audio-codec-y	:= audio_codec.o audio_helper.o
 gb-audio-gb-y		:= audio_gb.o
 gb-audio-apbridgea-y	:= audio_apbridgea.o
 gb-audio-manager-y	:= audio_manager.o audio_manager_module.o

drivers/staging/greybus/audio_codec.c

@@ -14,6 +14,7 @@
 #include "audio_codec.h"
 #include "audio_apbridgea.h"
 #include "audio_manager.h"
+#include "audio_helper.h"
 
 static struct gbaudio_codec_info *gbcodec;
 
@@ -865,7 +866,7 @@ int gbaudio_register_module(struct gbaudio_module_info *module)
 
 	/* card already instantiated, create widgets here only */
 	if (comp->card->instantiated) {
-		snd_soc_dapm_link_component_dai_widgets(comp->card,
+		gbaudio_dapm_link_component_dai_widgets(comp->card,
 							&comp->dapm);
 #ifdef CONFIG_SND_JACK
 		/*
@@ -999,13 +1000,16 @@ void gbaudio_unregister_module(struct gbaudio_module_info *module)
 	if (module->controls) {
 		dev_dbg(comp->dev, "Removing %d controls\n",
 			module->num_controls);
-		snd_soc_remove_codec_controls(comp, module->controls,
-					      module->num_controls);
+		/* release control semaphore */
+		up_write(&card->controls_rwsem);
+		gbaudio_remove_component_controls(comp, module->controls,
+						  module->num_controls);
+		down_write(&card->controls_rwsem);
 	}
 	if (module->dapm_widgets) {
 		dev_dbg(comp->dev, "Removing %d widgets\n",
 			module->num_dapm_widgets);
-		snd_soc_dapm_free_controls(&comp->dapm, module->dapm_widgets,
+		gbaudio_dapm_free_controls(&comp->dapm, module->dapm_widgets,
 					   module->num_dapm_widgets);
 	}
 

drivers/staging/greybus/audio_helper.c

@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Greybus Audio Sound SoC helper APIs
+ */
+
+#include <linux/debugfs.h>
+#include <sound/core.h>
+#include <sound/soc.h>
+#include <sound/soc-dapm.h>
+
+#define gbaudio_dapm_for_each_direction(dir) \
+	for ((dir) = SND_SOC_DAPM_DIR_IN; (dir) <= SND_SOC_DAPM_DIR_OUT; \
+		(dir)++)
+
+static void gbaudio_dapm_link_dai_widget(struct snd_soc_dapm_widget *dai_w,
+					 struct snd_soc_card *card)
+{
+	struct snd_soc_dapm_widget *w;
+	struct snd_soc_dapm_widget *src, *sink;
+	struct snd_soc_dai *dai = dai_w->priv;
+
+	/* ...find all widgets with the same stream and link them */
+	list_for_each_entry(w, &card->widgets, list) {
+		if (w->dapm != dai_w->dapm)
+			continue;
+
+		switch (w->id) {
+		case snd_soc_dapm_dai_in:
+		case snd_soc_dapm_dai_out:
+			continue;
+		default:
+			break;
+		}
+
+		if (!w->sname || !strstr(w->sname, dai_w->sname))
+			continue;
+
+		/*
+		 * check if widget is already linked,
+		 * if (w->linked)
+		 *	return;
+		 */
+
+		if (dai_w->id == snd_soc_dapm_dai_in) {
+			src = dai_w;
+			sink = w;
+		} else {
+			src = w;
+			sink = dai_w;
+		}
+		dev_dbg(dai->dev, "%s -> %s\n", src->name, sink->name);
+		/* Add the DAPM path and set widget's linked status
+		 * snd_soc_dapm_add_path(w->dapm, src, sink, NULL, NULL);
+		 * w->linked = 1;
+		 */
+	}
+}
+
+int gbaudio_dapm_link_component_dai_widgets(struct snd_soc_card *card,
+					    struct snd_soc_dapm_context *dapm)
+{
+	struct snd_soc_dapm_widget *dai_w;
+
+	/* For each DAI widget... */
+	list_for_each_entry(dai_w, &card->widgets, list) {
+		if (dai_w->dapm != dapm)
+			continue;
+		switch (dai_w->id) {
+		case snd_soc_dapm_dai_in:
+		case snd_soc_dapm_dai_out:
+			break;
+		default:
+			continue;
+		}
+		gbaudio_dapm_link_dai_widget(dai_w, card);
+	}
+
+	return 0;
+}
+
+static void gbaudio_dapm_free_path(struct snd_soc_dapm_path *path)
+{
+	list_del(&path->list_node[SND_SOC_DAPM_DIR_IN]);
+	list_del(&path->list_node[SND_SOC_DAPM_DIR_OUT]);
+	list_del(&path->list_kcontrol);
+	list_del(&path->list);
+	kfree(path);
+}
+
+static void gbaudio_dapm_free_widget(struct snd_soc_dapm_widget *w)
+{
+	struct snd_soc_dapm_path *p, *next_p;
+	enum snd_soc_dapm_direction dir;
+
+	list_del(&w->list);
+	/*
+	 * remove source and sink paths associated to this widget.
+	 * While removing the path, remove reference to it from both
+	 * source and sink widgets so that path is removed only once.
+	 */
+	gbaudio_dapm_for_each_direction(dir) {
+		snd_soc_dapm_widget_for_each_path_safe(w, dir, p, next_p)
+			gbaudio_dapm_free_path(p);
+	}
+
+	kfree(w->kcontrols);
+	kfree_const(w->name);
+	kfree_const(w->sname);
+	kfree(w);
+}
+
+int gbaudio_dapm_free_controls(struct snd_soc_dapm_context *dapm,
+			       const struct snd_soc_dapm_widget *widget,
+			       int num)
+{
+	int i;
+	struct snd_soc_dapm_widget *w, *next_w;
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *parent = dapm->debugfs_dapm;
+	struct dentry *debugfs_w = NULL;
+#endif
+
+	mutex_lock(&dapm->card->dapm_mutex);
+	for (i = 0; i < num; i++) {
+		/* below logic can be optimized to identify widget pointer */
+		list_for_each_entry_safe(w, next_w, &dapm->card->widgets,
+					 list) {
+			if (w->dapm != dapm)
+				continue;
+			if (!strcmp(w->name, widget->name))
+				break;
+			w = NULL;
+		}
+		if (!w) {
+			dev_err(dapm->dev, "%s: widget not found\n",
+				widget->name);
+			return -EINVAL;
+		}
+		widget++;
+#ifdef CONFIG_DEBUG_FS
+		if (!parent)
+			debugfs_w = debugfs_lookup(w->name, parent);
+		debugfs_remove(debugfs_w);
+		debugfs_w = NULL;
+#endif
+		gbaudio_dapm_free_widget(w);
+	}
+	mutex_unlock(&dapm->card->dapm_mutex);
+	return 0;
+}
+
+static int gbaudio_remove_controls(struct snd_card *card, struct device *dev,
+				   const struct snd_kcontrol_new *controls,
+				   int num_controls, const char *prefix)
+{
+	int i, err;
+
+	for (i = 0; i < num_controls; i++) {
+		const struct snd_kcontrol_new *control = &controls[i];
+		struct snd_ctl_elem_id id;
+		struct snd_kcontrol *kctl;
+
+		if (prefix)
+			snprintf(id.name, sizeof(id.name), "%s %s", prefix,
+				 control->name);
+		else
+			strlcpy(id.name, control->name, sizeof(id.name));
+		id.numid = 0;
+		id.iface = control->iface;
+		id.device = control->device;
+		id.subdevice = control->subdevice;
+		id.index = control->index;
+		kctl = snd_ctl_find_id(card, &id);
+		if (!kctl) {
+			dev_err(dev, "%d: Failed to find %s\n", err,
+				control->name);
+			continue;
+		}
+		err = snd_ctl_remove(card, kctl);
+		if (err < 0) {
+			dev_err(dev, "%d: Failed to remove %s\n", err,
+				control->name);
+			continue;
+		}
+	}
+	return 0;
+}
+
+int gbaudio_remove_component_controls(struct snd_soc_component *component,
+				      const struct snd_kcontrol_new *controls,
+				      unsigned int num_controls)
+{
+	struct snd_card *card = component->card->snd_card;
+
+	return gbaudio_remove_controls(card, component->dev, controls,
+				       num_controls, component->name_prefix);
+}

drivers/staging/greybus/audio_helper.h

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Greybus Audio Sound SoC helper APIs
+ */
+
+#ifndef __LINUX_GBAUDIO_HELPER_H
+#define __LINUX_GBAUDIO_HELPER_H
+
+int gbaudio_dapm_link_component_dai_widgets(struct snd_soc_card *card,
+					    struct snd_soc_dapm_context *dapm);
+int gbaudio_dapm_free_controls(struct snd_soc_dapm_context *dapm,
+			       const struct snd_soc_dapm_widget *widget,
+			       int num);
+int gbaudio_remove_component_controls(struct snd_soc_component *component,
+				      const struct snd_kcontrol_new *controls,
+				      unsigned int num_controls);
+#endif