pipewire/spa/plugins/alsa/acp/ext-volume.c

/* External Volume Control */
/* SPDX-FileCopyrightText: Copyright © 2026 Arun Raghavan */
/* SPDX-License-Identifier: MIT */

#include <spa/support/varlink.h>
#include <spa/utils/cleanup.h>
#include <spa/utils/json.h>
#include <spa/utils/json-builder.h>
#include <spa/utils/result.h>

#include "alsa-mixer.h"
#include "channelmap.h"
#include "volume.h"
#include "ext-volume.h"

#define VOLUME_CONTROL_BASE "org.pipewire.ExternalVolume."
#define METHOD_GET_CAPABILITIES VOLUME_CONTROL_BASE "GetCapabilities"
#define METHOD_READ_VOLUME VOLUME_CONTROL_BASE "ReadVolume"
#define METHOD_WRITE_VOLUME_ABSOLUTE VOLUME_CONTROL_BASE "WriteVolumeAbsolute"
#define METHOD_WRITE_VOLUME_RELATIVE VOLUME_CONTROL_BASE "WriteVolumeRelative"
#define METHOD_READ_MUTE VOLUME_CONTROL_BASE "ReadMute"
#define METHOD_WRITE_MUTE_VALUE VOLUME_CONTROL_BASE "WriteMuteValue"
#define METHOD_WRITE_MUTE_TOGGLE VOLUME_CONTROL_BASE "WriteMuteToggle"

static void client_disconnect(void *userdata)
{
	/* TODO: reconnect? bail? */
}

static void client_destroy(void *userdata)
{
	pa_log_debug("varlink client destroyed\n");
}

static struct spa_varlink_client_events client_events = {
	.disconnect = client_disconnect,
	.destroy = client_destroy,
};

static void check_reply(void *data, const char *params, const char *error,
		size_t len, bool continues)
{
	const char *method = (const char *) data;

	if (error != NULL)
		pa_log_error("Error calling %s: %s", method, error);
}

int
spa_acp_ext_volume_init(struct spa_acp_ext_volume *ext_volume, struct spa_varlink *varlink,
		const char *path, const char *device, const char *route)
{
	struct spa_json_builder params_json;
	struct spa_json reply_json;
	spa_autofree char *params = NULL;
	spa_autofree char *reply = NULL;
	char key[64];
	const char *str;
	size_t len;
	int res;

	pa_log_info("Connecting to external volume control at '%s'", path);

	ext_volume->client = spa_varlink_connect(varlink, path);

	if (!ext_volume->client) {
		pa_log_error("Could not connect to volume control service at: %s", path);
		return -EINVAL;
	}

	spa_varlink_client_add_listener(ext_volume->client, &ext_volume->listener, &client_events, ext_volume);

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_pop(&params_json, "}");

	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call_sync(ext_volume->client, METHOD_GET_CAPABILITIES, params, &reply);

	if (res < 0) {
		pa_log_error("Failed to query volume control capabilities: %s", spa_strerror(res));
		return res;
	}

	spa_json_begin_object(&reply_json, reply, res);

	while ((res = spa_json_object_next(&reply_json, key, sizeof(key), &str)) > 0) {
		struct spa_json sub;
		char key2[64];
		const char *val;
		int len;
		bool value;

		if (spa_streq(key, "error")) {
			pa_log_error("Error reading volume control capabilities: %s", str);
			res = -EINVAL;
			goto done;
		}

		if (!spa_streq(key, "parameters"))
			continue;

		len = spa_json_container_len(&reply_json, str, res);
		spa_json_begin_object(&sub, str, len);

		while ((len = spa_json_object_next(&sub, key2, sizeof(key2), &val)) > 0) {
			if (spa_streq(key2, "readVolume") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_READ_VOLUME;
			if (spa_streq(key2, "writeVolumeAbsolute") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_WRITE_VOLUME_VALUE;
			if (spa_streq(key2, "writeVolumeRelative") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_WRITE_VOLUME_UPDOWN;
			if (spa_streq(key2, "readMute") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_READ_MUTE;
			if (spa_streq(key2, "writeMuteValue") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_WRITE_MUTE_VALUE;
			if (spa_streq(key2, "writeMuteToggle") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_WRITE_MUTE_TOGGLE;
			if (spa_streq(key2, "readBalance") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_READ_BALANCE;
			if (spa_streq(key2, "writeBalance") && spa_json_parse_bool(val, len, &value) && value)
				ext_volume->flags |= SPA_AUDIO_VOLUME_CONTROL_WRITE_BALANCE;
		}

		break;
	}

	res = 0;
done:
	return res;
}

void
spa_acp_ext_volume_destroy(struct spa_acp_ext_volume *ext_volume)
{
	if (ext_volume->client) {
		spa_varlink_client_destroy(ext_volume->client);
		ext_volume->client = NULL;
	}
}

int
spa_acp_ext_volume_read_volume(struct spa_acp_ext_volume *ext_volume,
		const char *device, const char *route, pa_cvolume *cvol)
{
	struct spa_json_builder params_json;
	struct spa_json reply_json;
	spa_autofree char *params = NULL;
	spa_autofree char *reply = NULL;
	char key[64];
	const char *str;
	size_t len;
	int res;

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_object_string(&params_json, "route", route ? route : "");
	spa_json_builder_pop(&params_json, "}");

	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call_sync(ext_volume->client, METHOD_READ_VOLUME, params, &reply);

	if (res < 0) {
		pa_log_error("Failed to query volume : %s", spa_strerror(res));
		return res;
	}

	spa_json_begin_object(&reply_json, reply, res);

	while ((res = spa_json_object_next(&reply_json, key, sizeof(key), &str)) > 0) {
		struct spa_json sub = {0,}, volume_json;
		float v = 0;

		if (spa_streq(key, "error")) {
			pa_log_error("Error reading volume: %s", str);
			res = -EINVAL;
			goto done;
		}

		if (!spa_streq(key, "parameters"))
			continue;

		if (spa_json_enter_object(&reply_json, &sub) < 0) {
			pa_log_error("Could not read volume parameters");
			res = -EINVAL;
			goto done;
		}

		res = spa_json_object_find(&sub, "volume", &str);

		if (res < 0) {
			pa_log_error("Could not read volume");
			res = -EINVAL;
			goto done;
		}

		spa_json_enter_array(&sub, &volume_json);

		cvol->channels = 0;
		while (spa_json_get_float(&volume_json, &v) && cvol->channels < PA_CHANNELS_MAX) {
			cvol->values[cvol->channels++] = lrint(v * PA_VOLUME_NORM);
		}

		break;
	}

	res = 0;
done:
	return res;
}

int
spa_acp_ext_volume_write_volume_absolute(struct spa_acp_ext_volume *ext_volume,
		const char *device, const char *route, pa_cvolume *cvol)
{
	struct spa_json_builder params_json;
	spa_autofree char *params = NULL;
	size_t len;
	int i, res;

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_object_string(&params_json, "route", route ? route : "");

	spa_json_builder_object_push(&params_json, "volume", "[");

	/* FIXME: scale to the range from capabilities */
	if (ext_volume->flags & SPA_AUDIO_VOLUME_CONTROL_WRITE_BALANCE) {
		/* Write all channels */
		for (i = 0; i < (int)cvol->channels; i++)
			spa_json_builder_array_double(&params_json,
					(double) cvol->values[i] / PA_VOLUME_NORM);
	} else {
		/* Single volume */
		spa_json_builder_array_double(&params_json,
				(double) pa_cvolume_max(cvol) / PA_VOLUME_NORM);
	}

	spa_json_builder_pop(&params_json, "]");
	spa_json_builder_pop(&params_json, "}");
	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call(ext_volume->client, METHOD_WRITE_VOLUME_ABSOLUTE,
			params, false, false, check_reply, METHOD_WRITE_VOLUME_ABSOLUTE);

	if (res < 0) {
		pa_log_error("Failed to write volume: %s", spa_strerror(res));
		return res;
	}

	return res;
}

int
spa_acp_ext_volume_write_volume_relative(struct spa_acp_ext_volume *ext_volume,
		const char *device, const char *route, float step)
{
	struct spa_json_builder params_json;
	spa_autofree char *params = NULL;
	size_t len;
	int res;

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_object_string(&params_json, "route", route ? route : "");
	spa_json_builder_object_double(&params_json, "step", step);
	spa_json_builder_pop(&params_json, "}");

	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call(ext_volume->client, METHOD_WRITE_VOLUME_RELATIVE,
			params, false, false, check_reply, METHOD_WRITE_VOLUME_RELATIVE);

	if (res < 0) {
		pa_log_error("Failed to write volume: %s", spa_strerror(res));
		return res;
	}

	return res;
}

int
spa_acp_ext_volume_read_mute(struct spa_acp_ext_volume *ext_volume,
		const char *device, const char *route, bool *mute)
{
	struct spa_json_builder params_json;
	struct spa_json reply_json;
	spa_autofree char *params = NULL;
	spa_autofree char *reply = NULL;
	char key[64];
	const char *str;
	size_t len;
	int res;

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_object_string(&params_json, "route", route ? route : "");
	spa_json_builder_pop(&params_json, "}");

	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call_sync(ext_volume->client, METHOD_READ_MUTE, params, &reply);

	if (res < 0) {
		pa_log_error("Failed to query mute state: %s", spa_strerror(res));
		return res;
	}

	spa_json_begin_object(&reply_json, reply, res);

	while ((res = spa_json_object_next(&reply_json, key, sizeof(key), &str)) > 0) {
		struct spa_json sub = { 0, };

		if (spa_streq(key, "error")) {
			pa_log_error("Error reading mute state: %s", str);
			res = -EINVAL;
			goto done;
		}

		if (!spa_streq(key, "parameters"))
			continue;

		if (spa_json_enter_object(&reply_json, &sub) < 0) {
			pa_log_error("Could not read mute parameters");
			res = -EINVAL;
			goto done;
		}

		res = spa_json_object_find(&sub, "mute", &str);

		if (res < 0 || spa_json_get_bool(&reply_json, mute) < 0) {
			pa_log_error("Could not read mute");
			res = -EINVAL;
			goto done;
		}

		break;
	}

	res = 0;
done:
	return res;
}

int
spa_acp_ext_volume_write_mute_value(struct spa_acp_ext_volume *ext_volume,
		const char *device, const char *route, bool mute)
{
	struct spa_json_builder params_json;
	spa_autofree char *params = NULL;
	size_t len;
	int res;

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_object_string(&params_json, "route", route ? route : "");
	spa_json_builder_object_bool(&params_json, "mute", mute);
	spa_json_builder_pop(&params_json, "}");

	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call(ext_volume->client, METHOD_WRITE_MUTE_VALUE,
			params, false, false, check_reply, METHOD_WRITE_MUTE_VALUE);

	if (res < 0) {
		pa_log_error("Failed to write mute state: %s", spa_strerror(res));
		return res;
	}

	return res;
}

int
spa_acp_ext_volume_write_mute_toggle(struct spa_acp_ext_volume *ext_volume,
		const char *device, const char *route)
{
	struct spa_json_builder params_json;
	spa_autofree char *params = NULL;
	size_t len;
	int res;

	spa_json_builder_memstream(&params_json, &params, &len, 0);

	spa_json_builder_object_push(&params_json, NULL, "{");
	spa_json_builder_object_string(&params_json, "device", device ? device : "");
	spa_json_builder_object_string(&params_json, "route", route ? route : "");
	spa_json_builder_pop(&params_json, "}");

	spa_json_builder_close(&params_json);

	res = spa_varlink_client_call(ext_volume->client, METHOD_WRITE_MUTE_TOGGLE,
			params, false, false, check_reply, METHOD_WRITE_MUTE_TOGGLE);

	if (res < 0) {
		pa_log_error("Failed to write mute toggle: %s", spa_strerror(res));
		return res;
	}

	return 0;
}