[4/4] ASoC: codecs: Add support for the generic IIO auxiliary devices

diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index 4f78da914fc7..ee87e0125bfd 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -211,6 +211,7 @@  config SND_SOC_ALL_CODECS
 	imply SND_SOC_SGTL5000
 	imply SND_SOC_SI476X
 	imply SND_SOC_SIMPLE_AMPLIFIER
+	imply SND_SOC_SIMPLE_IIO_AUX
 	imply SND_SOC_SIMPLE_MUX
 	imply SND_SOC_SMA1303
 	imply SND_SOC_SPDIF
@@ -1555,6 +1556,17 @@  config SND_SOC_SIGMADSP_REGMAP
 config SND_SOC_SIMPLE_AMPLIFIER
 	tristate "Simple Audio Amplifier"
 
+config SND_SOC_SIMPLE_IIO_AUX
+	tristate "Simple 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-simple-iio-aux.
+
 config SND_SOC_SIMPLE_MUX
 	tristate "Simple Audio Mux"
 	depends on GPIOLIB
diff --git a/sound/soc/codecs/Makefile b/sound/soc/codecs/Makefile
index 11bd66d46f7b..f2b1ee22b57c 100644
--- a/sound/soc/codecs/Makefile
+++ b/sound/soc/codecs/Makefile
@@ -359,6 +359,7 @@  snd-soc-zl38060-objs := zl38060.o
 snd-soc-max9877-objs := max9877.o
 snd-soc-max98504-objs := max98504.o
 snd-soc-simple-amplifier-objs := simple-amplifier.o
+snd-soc-simple-iio-aux-objs := simple-iio-aux.o
 snd-soc-tpa6130a2-objs := tpa6130a2.o
 snd-soc-tas2552-objs := tas2552.o
 snd-soc-tas2562-objs := tas2562.o
@@ -729,6 +730,7 @@  obj-$(CONFIG_SND_SOC_ZL38060)	+= snd-soc-zl38060.o
 obj-$(CONFIG_SND_SOC_MAX9877)	+= snd-soc-max9877.o
 obj-$(CONFIG_SND_SOC_MAX98504)	+= snd-soc-max98504.o
 obj-$(CONFIG_SND_SOC_SIMPLE_AMPLIFIER)	+= snd-soc-simple-amplifier.o
+obj-$(CONFIG_SND_SOC_SIMPLE_IIO_AUX)	+= snd-soc-simple-iio-aux.o
 obj-$(CONFIG_SND_SOC_TPA6130A2)	+= snd-soc-tpa6130a2.o
 obj-$(CONFIG_SND_SOC_LPASS_MACRO_COMMON)	+= snd-soc-lpass-macro-common.o
 obj-$(CONFIG_SND_SOC_LPASS_WSA_MACRO)	+= snd-soc-lpass-wsa-macro.o
diff --git a/sound/soc/codecs/simple-iio-aux.c b/sound/soc/codecs/simple-iio-aux.c
new file mode 100644
index 000000000000..77f7fb11e416
--- /dev/null
+++ b/sound/soc/codecs/simple-iio-aux.c
@@ -0,0 +1,307 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// simple-iio-aux.c  --  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/module.h>
+#include <linux/slab.h>
+#include <sound/soc.h>
+#include <sound/tlv.h>
+
+struct simple_iio_aux_chan {
+	struct iio_channel *iio_chan;
+	const char *name;
+	bool is_inverted;
+	int max;
+	int min;
+};
+
+struct simple_iio_aux {
+	struct device *dev;
+	struct simple_iio_aux_chan *chans;
+	unsigned int num_chans;
+};
+
+static int simple_iio_aux_info_volsw(struct snd_kcontrol *kcontrol,
+				     struct snd_ctl_elem_info *uinfo)
+{
+	struct simple_iio_aux_chan *chan =
+		(struct simple_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 simple_iio_aux_get_volsw(struct snd_kcontrol *kcontrol,
+				    struct snd_ctl_elem_value *ucontrol)
+{
+	struct simple_iio_aux_chan *chan = (struct simple_iio_aux_chan *)kcontrol->private_value;
+	int max = chan->max;
+	int min = chan->min;
+	unsigned int mask = (1 << fls(max)) - 1;
+	unsigned int invert = chan->is_inverted;
+	int ret;
+	int val;
+
+	ret = iio_read_channel_raw(chan->iio_chan, &val);
+	if (ret < 0)
+		return ret;
+
+	ucontrol->value.integer.value[0] = (val & mask) - min;
+	if (invert)
+		ucontrol->value.integer.value[0] = max - ucontrol->value.integer.value[0];
+
+	return 0;
+}
+
+static int simple_iio_aux_put_volsw(struct snd_kcontrol *kcontrol,
+				    struct snd_ctl_elem_value *ucontrol)
+{
+	struct simple_iio_aux_chan *chan = (struct simple_iio_aux_chan *)kcontrol->private_value;
+	int max = chan->max;
+	int min = chan->min;
+	unsigned int mask = (1 << fls(max)) - 1;
+	unsigned int invert = chan->is_inverted;
+	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) & mask;
+	if (invert)
+		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 simple_iio_aux_add_controls(struct snd_soc_component *component,
+				       struct simple_iio_aux_chan *chan)
+{
+	struct snd_kcontrol_new control = {0};
+
+	control.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
+	control.name = chan->name;
+	control.info = simple_iio_aux_info_volsw;
+	control.get = simple_iio_aux_get_volsw;
+	control.put = simple_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] = {0};
+static struct snd_soc_dapm_route routes[2] = {0};
+
+static int simple_iio_aux_add_dapms(struct snd_soc_component *component,
+				    struct simple_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 end;
+	}
+	output_name = kasprintf(GFP_KERNEL, "%s OUT", chan->name);
+	if (!output_name) {
+		ret = -ENOMEM;
+		goto end;
+	}
+	pga_name = kasprintf(GFP_KERNEL, "%s PGA", chan->name);
+	if (!pga_name) {
+		ret = -ENOMEM;
+		goto end;
+	}
+
+	BUILD_BUG_ON(ARRAY_SIZE(widgets) < 3);
+	widgets[0] = SND_SOC_DAPM_WIDGET(SND_SOC_DAPM_INPUT(input_name));
+	widgets[1] = SND_SOC_DAPM_WIDGET(SND_SOC_DAPM_OUTPUT(output_name));
+	widgets[2] = SND_SOC_DAPM_WIDGET(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 end;
+
+	BUILD_BUG_ON(ARRAY_SIZE(routes) < 2);
+	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);
+
+end:
+	/* Allocated names are no more needed (duplicated in ASoC internals) */
+	kfree(pga_name);
+	kfree(output_name);
+	kfree(input_name);
+
+	return ret;
+}
+
+static int simple_iio_aux_component_probe(struct snd_soc_component *component)
+{
+	struct simple_iio_aux *iio_aux = snd_soc_component_get_drvdata(component);
+	struct simple_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) {
+			dev_err(component->dev, "chan[%d] %s: Cannot get max raw value (%d)\n",
+				i, chan->name, ret);
+			return ret;
+		}
+
+		ret = iio_read_min_channel_raw(chan->iio_chan, &chan->min);
+		if (ret) {
+			dev_err(component->dev, "chan[%d] %s: Cannot get min raw value (%d)\n",
+				i, chan->name, ret);
+			return ret;
+		}
+
+		/* Set initial value */
+		ret = iio_write_channel_raw(chan->iio_chan,
+					    chan->is_inverted ? chan->max : chan->min);
+		if (ret) {
+			dev_err(component->dev, "chan[%d] %s: Cannot set initial value (%d)\n",
+				i, chan->name, ret);
+			return ret;
+		}
+
+		ret = simple_iio_aux_add_controls(component, chan);
+		if (ret)
+			return ret;
+
+		ret = simple_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,
+			chan->is_inverted ? "on" : "off");
+	}
+
+	return 0;
+}
+
+static const struct snd_soc_component_driver simple_iio_aux_component_driver = {
+	.probe = simple_iio_aux_component_probe,
+};
+
+static int simple_iio_aux_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct simple_iio_aux_chan *iio_aux_chan;
+	struct simple_iio_aux *iio_aux;
+	int count;
+	u32 tmp;
+	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 = of_property_count_strings(np, "io-channel-names");
+	if (count < 0) {
+		dev_err(iio_aux->dev, "%pOF: failed to read io-channel-names\n", np);
+		return count;
+	}
+
+	iio_aux->chans = devm_kmalloc_array(&pdev->dev, count,
+					    sizeof(*iio_aux->chans), GFP_KERNEL);
+	if (!iio_aux->chans)
+		return -ENOMEM;
+	iio_aux->num_chans = count;
+
+	for (i = 0; i < iio_aux->num_chans; i++) {
+		iio_aux_chan = iio_aux->chans + i;
+
+		ret = of_property_read_string_index(np, "io-channel-names", i,
+						    &iio_aux_chan->name);
+		if (ret < 0) {
+			dev_err(iio_aux->dev, "%pOF: failed to read io-channel-names[%d]\n", np, i);
+			return ret;
+		}
+
+		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);
+			return dev_err_probe(iio_aux->dev, ret,
+					     "get IIO channel '%s' failed (%d)\n",
+					     iio_aux_chan->name, ret);
+		}
+
+		tmp = 0;
+		of_property_read_u32_index(np, "invert", i, &tmp);
+		iio_aux_chan->is_inverted = !!tmp;
+	}
+
+	platform_set_drvdata(pdev, iio_aux);
+
+	return devm_snd_soc_register_component(iio_aux->dev,
+					       &simple_iio_aux_component_driver,
+					       NULL, 0);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id simple_iio_aux_ids[] = {
+	{ .compatible = "simple-iio-aux", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, simple_iio_aux_ids);
+#endif
+
+static struct platform_driver simple_iio_aux_driver = {
+	.driver = {
+		.name = "simple-iio-aux",
+		.of_match_table = of_match_ptr(simple_iio_aux_ids),
+	},
+	.probe = simple_iio_aux_probe,
+};
+
+module_platform_driver(simple_iio_aux_driver);
+
+MODULE_AUTHOR("Herve Codina <herve.codina@bootlin.com>");
+MODULE_DESCRIPTION("IIO ALSA SoC aux driver");
+MODULE_LICENSE("GPL");