Date:   Thu, 17 Nov 2016 00:48:29 +0100
From:   Peter Rosin <peda@...ntia.se>
To:     <linux-kernel@...r.kernel.org>
CC:     Peter Rosin <peda@...ntia.se>, Wolfram Sang <wsa@...-dreams.de>,
        "Rob Herring" <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Jonathan Cameron" <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        "Lars-Peter Clausen" <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        "Arnd Bergmann" <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-iio@...r.kernel.org>
Subject: [RFC PATCH 5/7] iio: multiplexer: new iio category and iio-mux driver

When a multiplexer changes how an iio device behaves (for example
by feeding different signals to an ADC), this driver can be used
create one virtual iio channel for each multiplexer state.

Depends on the generic multiplexer driver.
---
 drivers/iio/Kconfig               |   1 +
 drivers/iio/Makefile              |   1 +
 drivers/iio/multiplexer/Kconfig   |  17 +++
 drivers/iio/multiplexer/Makefile  |   6 +
 drivers/iio/multiplexer/iio-mux.c | 313 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 338 insertions(+)
 create mode 100644 drivers/iio/multiplexer/Kconfig
 create mode 100644 drivers/iio/multiplexer/Makefile
 create mode 100644 drivers/iio/multiplexer/iio-mux.c

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 6743b18194fb..dcb541d0d70e 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -82,6 +82,7 @@ source "drivers/iio/humidity/Kconfig"
 source "drivers/iio/imu/Kconfig"
 source "drivers/iio/light/Kconfig"
 source "drivers/iio/magnetometer/Kconfig"
+source "drivers/iio/multiplexer/Kconfig"
 source "drivers/iio/orientation/Kconfig"
 if IIO_TRIGGER
    source "drivers/iio/trigger/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 87e4c4369e2f..f9879c29cf6f 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -27,6 +27,7 @@ obj-y += humidity/
 obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/
+obj-y += multiplexer/
 obj-y += orientation/
 obj-y += potentiometer/
 obj-y += pressure/
diff --git a/drivers/iio/multiplexer/Kconfig b/drivers/iio/multiplexer/Kconfig
new file mode 100644
index 000000000000..31cbe4509366
--- /dev/null
+++ b/drivers/iio/multiplexer/Kconfig
@@ -0,0 +1,17 @@
+#
+# Multiplexer drivers
+#
+# When adding new entries keep the list in alphabetical order
+
+menu "Multiplexers"
+
+config IIO_MUX
+	tristate "IIO multiplexer driver"
+	depends on OF && MUX_GPIO
+	help
+	  Say yes here to build support for the IIO multiplexer.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called iio-mux.
+
+endmenu
diff --git a/drivers/iio/multiplexer/Makefile b/drivers/iio/multiplexer/Makefile
new file mode 100644
index 000000000000..68be3c4abd07
--- /dev/null
+++ b/drivers/iio/multiplexer/Makefile
@@ -0,0 +1,6 @@
+#
+# Makefile for industrial I/O multiplexer drivers
+#
+
+# When adding new entries keep the list in alphabetical order
+obj-$(CONFIG_IIO_MUX) += iio-mux.o
diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
new file mode 100644
index 000000000000..6f6644fb9342
--- /dev/null
+++ b/drivers/iio/multiplexer/iio-mux.c
@@ -0,0 +1,313 @@
+/*
+ * IIO multiplexer driver
+ *
+ * Copyright (C) 2016 Axentia Technologies AB
+ *
+ * Author: Peter Rosin <peda@...ntia.se>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/err.h>
+#include <linux/iio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/mux.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct mux_child {
+	u32 reg;
+
+	const char **ext_info;
+	int num_ext_info;
+};
+
+struct mux {
+	u32 cache;
+	struct mux_control *control;
+	struct iio_channel *parent;
+	struct iio_dev *indio_dev;
+	struct iio_chan_spec *c;
+	struct mux_child *child;
+};
+
+static int iio_mux_select(struct mux *mux, int idx)
+{
+	struct mux_child *child = &mux->child[idx];
+	int ret;
+	int i;
+
+	ret = mux_control_select(mux->control, child->reg);
+	if (ret < 0)
+		return ret;
+
+	if (mux->cache == child->reg)
+		return 0;
+
+	for (i = 0; i < child->num_ext_info - 1; i += 2) {
+		const char *value = child->ext_info[i + 1];
+
+		ret = iio_write_channel_ext_info(mux->parent,
+						 child->ext_info[i],
+						 value, strlen(value));
+		if (ret < 0) {
+			mux_control_deselect(mux->control);
+			return ret;
+		}
+	}
+	mux->cache = child->reg;
+
+	return 0;
+}
+
+static void iio_mux_deselect(struct mux *mux)
+{
+	mux_control_deselect(mux->control);
+}
+
+static int mux_read_raw(struct iio_dev *indio_dev,
+			struct iio_chan_spec const *chan,
+			int *val, int *val2, long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_read_channel_raw(mux->parent, val);
+		break;
+
+	case IIO_CHAN_INFO_SCALE:
+		ret = iio_read_channel_scale(mux->parent, val, val2);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static int mux_read_avail(struct iio_dev *indio_dev,
+			  struct iio_chan_spec const *chan,
+			  const int **vals, int *type, int *length,
+			  long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*type = IIO_VAL_INT;
+		ret = iio_read_avail_channel_raw(mux->parent, vals, length);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static int mux_write_raw(struct iio_dev *indio_dev,
+			 struct iio_chan_spec const *chan,
+			 int val, int val2, long mask)
+{
+	struct mux *mux = iio_priv(indio_dev);
+	int idx = chan - mux->c;
+	int ret;
+
+	ret = iio_mux_select(mux, idx);
+	if (ret < 0)
+		return ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = iio_write_channel_raw(mux->parent, val);
+		break;
+
+	default:
+		ret = -EINVAL;
+	}
+
+	iio_mux_deselect(mux);
+
+	return ret;
+}
+
+static const struct iio_info mux_info = {
+	.read_raw = mux_read_raw,
+	.read_avail = mux_read_avail,
+	.write_raw = mux_write_raw,
+	.driver_module = THIS_MODULE,
+};
+
+static int mux_configure_channel(struct device *dev, struct mux *mux,
+				 struct device_node *child_np, int idx)
+{
+	struct mux_child *child = &mux->child[idx];
+	struct iio_chan_spec *c = &mux->c[idx];
+	const struct iio_chan_spec *pc = mux->parent->channel;
+	int i;
+	int ret;
+
+	c->indexed = 1;
+	c->channel = idx;
+	c->output = pc->output;
+	c->datasheet_name = child_np->name;
+
+	ret = iio_get_channel_type(mux->parent, &c->type);
+	if (ret < 0) {
+		dev_err(dev, "failed to get parent channel type\n");
+		return ret;
+	}
+
+	if (iio_channel_has_info(pc, IIO_CHAN_INFO_RAW))
+		c->info_mask_separate |= BIT(IIO_CHAN_INFO_RAW);
+	if (iio_channel_has_info(pc, IIO_CHAN_INFO_SCALE))
+		c->info_mask_separate |= BIT(IIO_CHAN_INFO_SCALE);
+
+	if (iio_channel_has_available(pc, IIO_CHAN_INFO_RAW))
+		c->info_mask_separate_available |= BIT(IIO_CHAN_INFO_RAW);
+
+	ret = of_property_read_u32(child_np, "reg", &child->reg);
+	if (ret < 0) {
+		dev_err(dev, "no reg property for node '%s'\n", child_np->name);
+		return ret;
+	}
+
+	for (i = 0; i < idx; ++i) {
+		if (mux->child[i].reg == child->reg) {
+			dev_err(dev, "double use of reg %d\n", child->reg);
+			return -EINVAL;
+		}
+	}
+
+	ret = of_property_read_string_array(child_np, "iio-ext-info", NULL, 0);
+	if (ret <= 0)
+		return 0;
+
+	child->ext_info = devm_kzalloc(dev, sizeof(*child->ext_info) * ret,
+				       GFP_KERNEL);
+	if (!child->ext_info)
+		return -ENOMEM;
+
+	child->num_ext_info = ret;
+	ret = of_property_read_string_array(child_np, "iio-ext-info",
+					    child->ext_info,
+					    child->num_ext_info);
+	if (ret != child->num_ext_info)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int mux_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *child_np;
+	struct iio_dev *indio_dev;
+	struct mux *mux;
+	int children;
+	int sizeof_priv;
+	int idx;
+	int ret;
+
+	if (!np)
+		return -ENODEV;
+
+	children = of_get_child_count(np);
+	if (children <= 0) {
+		dev_err(dev, "not even a single child\n");
+		return -EINVAL;
+	}
+
+	sizeof_priv = sizeof(*mux);
+	sizeof_priv += sizeof(*mux->child) * children;
+	sizeof_priv += sizeof(*mux->c) * children;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof_priv);
+	if (!indio_dev)
+		return -ENOMEM;
+
+	mux = iio_priv(indio_dev);
+	mux->child = (struct mux_child *)(mux + 1);
+	mux->c = (struct iio_chan_spec *)(mux->child + children);
+
+	platform_set_drvdata(pdev, indio_dev);
+
+	mux->parent = devm_iio_channel_get(dev, "parent");
+	if (IS_ERR(mux->parent)) {
+		if (PTR_ERR(mux->parent) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get parent channel\n");
+		return PTR_ERR(mux->parent);
+	}
+
+	indio_dev->name = dev_name(dev);
+	indio_dev->dev.parent = dev;
+	indio_dev->info = &mux_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = mux->c;
+	indio_dev->num_channels = children;
+
+	idx = 0;
+	for_each_child_of_node(np, child_np) {
+		ret = mux_configure_channel(dev, mux, child_np, idx);
+		if (ret < 0)
+			return ret;
+		idx++;
+	}
+
+	mux->control = devm_mux_control_get(dev, "mux");
+	if (IS_ERR(mux->control)) {
+		if (PTR_ERR(mux->control) != -EPROBE_DEFER)
+			dev_err(dev, "failed to get control-mux\n");
+		return PTR_ERR(mux->control);
+	}
+
+	ret = devm_iio_device_register(dev, indio_dev);
+	if (ret) {
+		dev_err(dev, "failed to register iio device\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mux_match[] = {
+	{ .compatible = "iio-mux" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mux_match);
+
+static struct platform_driver mux_driver = {
+	.probe = mux_probe,
+	.driver = {
+		.name = "iio-mux",
+		.of_match_table = mux_match,
+	},
+};
+module_platform_driver(mux_driver);
+
+MODULE_DESCRIPTION("IIO multiplexer driver");
+MODULE_AUTHOR("Peter Rosin <peda@...ntia.se>");
+MODULE_LICENSE("GPL v2");
-- 
2.1.4

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