[v3,11/12] ASoC: codecs: Add support for the generic IIO auxiliary devices

diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index 44806bfe8ee5..92b7c417f1b2 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -53,6 +53,7 @@  config SND_SOC_ALL_CODECS
 	imply SND_SOC_AK5558
 	imply SND_SOC_ALC5623
 	imply SND_SOC_ALC5632
+	imply SND_SOC_AUDIO_IIO_AUX
 	imply SND_SOC_AW8738
 	imply SND_SOC_AW88395
 	imply SND_SOC_BT_SCO
@@ -608,6 +609,17 @@  config SND_SOC_ALC5632
 	tristate
 	depends on I2C
 
+config SND_SOC_AUDIO_IIO_AUX
+	tristate "Audio IIO Auxiliary device"
+	depends on IIO
+	help
+	  Enable support for Industrial I/O devices as audio auxiliary devices.
+	  This allows to have an IIO device present in the audio path and
+	  controlled using mixer controls.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called snd-soc-audio-iio-aux.
+
 config SND_SOC_AW8738
 	tristate "Awinic AW8738 Audio Amplifier"
 	select GPIOLIB
diff --git a/sound/soc/codecs/Makefile b/sound/soc/codecs/Makefile
index 2c45c2f97e4e..f2828d3616c5 100644
--- a/sound/soc/codecs/Makefile
+++ b/sound/soc/codecs/Makefile
@@ -45,6 +45,7 @@  snd-soc-ak4671-objs := ak4671.o
 snd-soc-ak5386-objs := ak5386.o
 snd-soc-ak5558-objs := ak5558.o
 snd-soc-arizona-objs := arizona.o arizona-jack.o
+snd-soc-audio-iio-aux-objs := audio-iio-aux.o
 snd-soc-aw8738-objs := aw8738.o
 snd-soc-aw88395-lib-objs := aw88395/aw88395_lib.o
 snd-soc-aw88395-objs := aw88395/aw88395.o \
@@ -421,6 +422,7 @@  obj-$(CONFIG_SND_SOC_AK5558)	+= snd-soc-ak5558.o
 obj-$(CONFIG_SND_SOC_ALC5623)    += snd-soc-alc5623.o
 obj-$(CONFIG_SND_SOC_ALC5632)	+= snd-soc-alc5632.o
 obj-$(CONFIG_SND_SOC_ARIZONA)	+= snd-soc-arizona.o
+obj-$(CONFIG_SND_SOC_AUDIO_IIO_AUX)	+= snd-soc-audio-iio-aux.o
 obj-$(CONFIG_SND_SOC_AW8738)	+= snd-soc-aw8738.o
 obj-$(CONFIG_SND_SOC_AW88395_LIB) += snd-soc-aw88395-lib.o
 obj-$(CONFIG_SND_SOC_AW88395)	+=snd-soc-aw88395.o
diff --git a/sound/soc/codecs/audio-iio-aux.c b/sound/soc/codecs/audio-iio-aux.c
new file mode 100644
index 000000000000..94fc8b6767d0
--- /dev/null
+++ b/sound/soc/codecs/audio-iio-aux.c
@@ -0,0 +1,334 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// ALSA SoC glue to use IIO devices as audio components
+//
+// Copyright 2023 CS GROUP France
+//
+// Author: Herve Codina <herve.codina@bootlin.com>
+
+#include <linux/iio/consumer.h>
+#include <linux/minmax.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <sound/soc.h>
+#include <linux/string_helpers.h>
+#include <sound/tlv.h>
+
+struct audio_iio_aux_chan {
+	struct iio_channel *iio_chan;
+	const char *name;
+	int max;
+	int min;
+	bool is_invert_range;
+};
+
+struct audio_iio_aux {
+	struct device *dev;
+	struct audio_iio_aux_chan *chans;
+	unsigned int num_chans;
+};
+
+static int audio_iio_aux_info_volsw(struct snd_kcontrol *kcontrol,
+				    struct snd_ctl_elem_info *uinfo)
+{
+	struct audio_iio_aux_chan *chan = (struct audio_iio_aux_chan *)kcontrol->private_value;
+
+	uinfo->count = 1;
+	uinfo->value.integer.min = 0;
+	uinfo->value.integer.max = chan->max - chan->min;
+	uinfo->type = (uinfo->value.integer.max == 1) ?
+			SNDRV_CTL_ELEM_TYPE_BOOLEAN : SNDRV_CTL_ELEM_TYPE_INTEGER;
+	return 0;
+}
+
+static int audio_iio_aux_get_volsw(struct snd_kcontrol *kcontrol,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct audio_iio_aux_chan *chan = (struct audio_iio_aux_chan *)kcontrol->private_value;
+	int max = chan->max;
+	int min = chan->min;
+	bool invert_range = chan->is_invert_range;
+	int ret;
+	int val;
+
+	ret = iio_read_channel_raw(chan->iio_chan, &val);
+	if (ret < 0)
+		return ret;
+
+	ucontrol->value.integer.value[0] = val - min;
+	if (invert_range)
+		ucontrol->value.integer.value[0] = max - ucontrol->value.integer.value[0];
+
+	return 0;
+}
+
+static int audio_iio_aux_put_volsw(struct snd_kcontrol *kcontrol,
+				   struct snd_ctl_elem_value *ucontrol)
+{
+	struct audio_iio_aux_chan *chan = (struct audio_iio_aux_chan *)kcontrol->private_value;
+	int max = chan->max;
+	int min = chan->min;
+	bool invert_range = chan->is_invert_range;
+	int val;
+	int ret;
+	int tmp;
+
+	val = ucontrol->value.integer.value[0];
+	if (val < 0)
+		return -EINVAL;
+	if (val > max - min)
+		return -EINVAL;
+
+	val = val + min;
+	if (invert_range)
+		val = max - val;
+
+	ret = iio_read_channel_raw(chan->iio_chan, &tmp);
+	if (ret < 0)
+		return ret;
+
+	if (tmp == val)
+		return 0;
+
+	ret = iio_write_channel_raw(chan->iio_chan, val);
+	if (ret)
+		return ret;
+
+	return 1; /* The value changed */
+}
+
+static int audio_iio_aux_add_controls(struct snd_soc_component *component,
+				      struct audio_iio_aux_chan *chan)
+{
+	struct snd_kcontrol_new control = {0};
+
+	control.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
+	control.name = chan->name;
+	control.info = audio_iio_aux_info_volsw;
+	control.get = audio_iio_aux_get_volsw;
+	control.put = audio_iio_aux_put_volsw;
+	control.private_value = (unsigned long)chan;
+
+	return snd_soc_add_component_controls(component, &control, 1);
+}
+
+/*
+ * These data could be on stack but they are pretty big.
+ * As ASoC internally copy them and protect them against concurrent accesses
+ * (snd_soc_bind_card() protects using client_mutex), keep them in the global
+ * data area.
+ */
+static struct snd_soc_dapm_widget widgets[3];
+static struct snd_soc_dapm_route routes[2];
+
+/* Be sure sizes are correct (need 3 widgets and 2 routes) */
+static_assert(ARRAY_SIZE(widgets) >= 3, "3 widgets are needed");
+static_assert(ARRAY_SIZE(routes) >= 2, "2 routes are needed");
+
+static int audio_iio_aux_add_dapms(struct snd_soc_component *component,
+				   struct audio_iio_aux_chan *chan)
+{
+	struct snd_soc_dapm_context *dapm = snd_soc_component_get_dapm(component);
+	char *input_name = NULL;
+	char *output_name = NULL;
+	char *pga_name = NULL;
+	int ret;
+
+	input_name = kasprintf(GFP_KERNEL, "%s IN", chan->name);
+	if (!input_name) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	output_name = kasprintf(GFP_KERNEL, "%s OUT", chan->name);
+	if (!output_name) {
+		ret = -ENOMEM;
+		goto out_free_input_name;
+	}
+	pga_name = kasprintf(GFP_KERNEL, "%s PGA", chan->name);
+	if (!pga_name) {
+		ret = -ENOMEM;
+		goto out_free_output_name;
+	}
+
+	widgets[0] = SND_SOC_DAPM_INPUT(input_name);
+	widgets[1] = SND_SOC_DAPM_OUTPUT(output_name);
+	widgets[2] = SND_SOC_DAPM_PGA(pga_name, SND_SOC_NOPM, 0, 0, NULL, 0);
+	ret = snd_soc_dapm_new_controls(dapm, widgets, 3);
+	if (ret)
+		goto out_free_pga_name;
+
+	routes[0].sink = pga_name;
+	routes[0].control = NULL;
+	routes[0].source = input_name;
+	routes[1].sink = output_name;
+	routes[1].control = NULL;
+	routes[1].source = pga_name;
+	ret = snd_soc_dapm_add_routes(dapm, routes, 2);
+
+	/* Allocated names are no more needed (duplicated in ASoC internals) */
+
+out_free_pga_name:
+	kfree(pga_name);
+out_free_output_name:
+	kfree(output_name);
+out_free_input_name:
+	kfree(input_name);
+out:
+	return ret;
+}
+
+static int audio_iio_aux_component_probe(struct snd_soc_component *component)
+{
+	struct audio_iio_aux *iio_aux = snd_soc_component_get_drvdata(component);
+	struct audio_iio_aux_chan *chan;
+	int ret;
+	int i;
+
+	for (i = 0; i < iio_aux->num_chans; i++) {
+		chan = iio_aux->chans + i;
+
+		ret = iio_read_max_channel_raw(chan->iio_chan, &chan->max);
+		if (ret)
+			return dev_err_probe(component->dev, ret,
+					     "chan[%d] %s: Cannot get max raw value\n",
+					     i, chan->name);
+
+		ret = iio_read_min_channel_raw(chan->iio_chan, &chan->min);
+		if (ret)
+			return dev_err_probe(component->dev, ret,
+					     "chan[%d] %s: Cannot get min raw value\n",
+					     i, chan->name);
+
+		if (chan->min > chan->max) {
+			dev_dbg(component->dev, "chan[%d] %s: Swap min and max\n",
+				i, chan->name);
+			swap(chan->min, chan->max);
+		}
+
+		/* Set initial value */
+		ret = iio_write_channel_raw(chan->iio_chan,
+					    chan->is_invert_range ? chan->max : chan->min);
+		if (ret)
+			return dev_err_probe(component->dev, ret,
+					     "chan[%d] %s: Cannot set initial value\n",
+					     i, chan->name);
+
+		ret = audio_iio_aux_add_controls(component, chan);
+		if (ret)
+			return ret;
+
+		ret = audio_iio_aux_add_dapms(component, chan);
+		if (ret)
+			return ret;
+
+		dev_dbg(component->dev, "chan[%d]: Added %s (min=%d, max=%d, invert=%s)\n",
+			i, chan->name, chan->min, chan->max,
+			str_on_off(chan->is_invert_range));
+	}
+
+	return 0;
+}
+
+static const struct snd_soc_component_driver audio_iio_aux_component_driver = {
+	.probe = audio_iio_aux_component_probe,
+};
+
+static int audio_iio_aux_probe(struct platform_device *pdev)
+{
+	struct audio_iio_aux_chan *iio_aux_chan;
+	struct audio_iio_aux *iio_aux;
+	const char **names;
+	u32 *invert_ranges;
+	int count;
+	int ret;
+	int i;
+
+	iio_aux = devm_kzalloc(&pdev->dev, sizeof(*iio_aux), GFP_KERNEL);
+	if (!iio_aux)
+		return -ENOMEM;
+
+	iio_aux->dev = &pdev->dev;
+
+	count = device_property_string_array_count(iio_aux->dev, "io-channel-names");
+	if (count < 0)
+		return dev_err_probe(iio_aux->dev, count, "failed to count io-channel-names\n");
+
+	iio_aux->num_chans = count;
+
+	iio_aux->chans = devm_kmalloc_array(iio_aux->dev, iio_aux->num_chans,
+					    sizeof(*iio_aux->chans), GFP_KERNEL);
+	if (!iio_aux->chans)
+		return -ENOMEM;
+
+	names = kcalloc(iio_aux->num_chans, sizeof(*names), GFP_KERNEL);
+	if (!names)
+		return -ENOMEM;
+
+	invert_ranges = kcalloc(iio_aux->num_chans, sizeof(*invert_ranges), GFP_KERNEL);
+	if (!invert_ranges) {
+		ret = -ENOMEM;
+		goto out_free_names;
+	}
+
+	ret = device_property_read_string_array(iio_aux->dev, "io-channel-names",
+						names, iio_aux->num_chans);
+	if (ret < 0) {
+		dev_err_probe(iio_aux->dev, ret, "failed to read io-channel-names\n");
+		goto out_free_invert_ranges;
+	}
+
+	/*
+	 * snd-control-invert-range is optional and can contain fewer items
+	 * than the number of channel. Unset values default to 0.
+	 */
+	count = device_property_count_u32(iio_aux->dev, "snd-control-invert-range");
+	if (count > 0) {
+		count = min_t(unsigned int, count, iio_aux->num_chans);
+		device_property_read_u32_array(iio_aux->dev, "snd-control-invert-range",
+					       invert_ranges, count);
+	}
+
+	for (i = 0; i < iio_aux->num_chans; i++) {
+		iio_aux_chan = iio_aux->chans + i;
+		iio_aux_chan->name = names[i];
+		iio_aux_chan->is_invert_range = invert_ranges[i];
+
+		iio_aux_chan->iio_chan = devm_iio_channel_get(iio_aux->dev, iio_aux_chan->name);
+		if (IS_ERR(iio_aux_chan->iio_chan)) {
+			ret = PTR_ERR(iio_aux_chan->iio_chan);
+			dev_err_probe(iio_aux->dev, ret, "get IIO channel '%s' failed\n",
+				      iio_aux_chan->name);
+			goto out_free_invert_ranges;
+		}
+	}
+
+	platform_set_drvdata(pdev, iio_aux);
+
+	ret = devm_snd_soc_register_component(iio_aux->dev, &audio_iio_aux_component_driver,
+					      NULL, 0);
+out_free_invert_ranges:
+	kfree(invert_ranges);
+out_free_names:
+	kfree(names);
+	return ret;
+}
+
+static const struct of_device_id audio_iio_aux_ids[] = {
+	{ .compatible = "audio-iio-aux" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, audio_iio_aux_ids);
+
+static struct platform_driver audio_iio_aux_driver = {
+	.driver = {
+		.name = "audio-iio-aux",
+		.of_match_table = audio_iio_aux_ids,
+	},
+	.probe = audio_iio_aux_probe,
+};
+module_platform_driver(audio_iio_aux_driver);
+
+MODULE_AUTHOR("Herve Codina <herve.codina@bootlin.com>");
+MODULE_DESCRIPTION("IIO ALSA SoC aux driver");
+MODULE_LICENSE("GPL");