[PATCH v2 4/4] iio: Add OF support

[Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>]

Provide bindings and parse OF data during initialization.

Signed-off-by: Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>
---
- Documentation update per feedback
- Dropped io-channel-output-names from the bindings document. The property is
  not used in the code, and it is not entirely clear what it would be used for.
  If there is a need for it, we can add it back in later on.
- Don't export OF specific API calls
- For OF support, no longer depend on iio_map
- Add #ifdef CONFIG_OF where appropriate, and ensure that the code still builds
  if it is not selected.
- Change iio_channel_get to take device pointer as argument instead of device
  name. Retain old API as of_iio_channel_get_sys.
- iio_channel_get now works for both OF and non-OF configurations.

 .../devicetree/bindings/iio/iio-bindings.txt       |   76 ++++++++
 drivers/iio/inkern.c                               |  186 ++++++++++++++++++++
 2 files changed, 262 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/iio-bindings.txt

diff --git a/Documentation/devicetree/bindings/iio/iio-bindings.txt b/Documentation/devicetree/bindings/iio/iio-bindings.txt
new file mode 100644
index 0000000..58df5f6
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/iio-bindings.txt
@@ -0,0 +1,76 @@
+This binding is a work-in-progress. It is derived from clock bindings,
+and based on suggestions from Lars-Peter Clausen [1].
+
+Sources of IIO channels can be represented by any node in the device
+tree.  Those nodes are designated as IIO providers.  IIO consumer
+nodes use a phandle and IIO specifier pair to connect IIO provider
+outputs to IIO inputs.  Similar to the gpio specifiers, an IIO
+specifier is an array of one or more cells identifying the IIO
+output on a device.  The length of an IIO specifier is defined by the
+value of a #io-channel-cells property in the clock provider node.
+
+[1] http://marc.info/?l=linux-iio&m=135902119507483&w=2
+
+==IIO providers==
+
+Required properties:
+#io-channel-cells: Number of cells in an IIO specifier; Typically 0 for nodes
+		   with a single IIO output and 1 for nodes with multiple
+		   IIO outputs.
+
+For example:
+
+    adc: adc@35 {
+	compatible = "maxim,max1139";
+	reg = <0x35>;
+        #io-channel-cells = <1>;
+    };
+
+==IIO consumers==
+
+Required properties:
+io-channels:	List of phandle and IIO specifier pairs, one pair
+		for each IIO input to the device.  Note: if the
+		IIO provider specifies '0' for #clock-cells, then
+		only the phandle portion of the pair will appear.
+
+Optional properties:
+io-channel-names:
+		List of IIO input name strings sorted in the same
+		order as the io-channels property.  Consumers drivers
+		will use io-channel-names to match IIO input names
+		with IIO specifiers.
+io-channel-ranges:
+		Empty property indicating that child nodes can inherit named
+		IIO channels from this node. Useful for bus nodes to provide
+		and IIO channel to their children.
+
+For example:
+
+    device {
+        io-channels = <&adc 1>, <&ref 0>;
+        io-channel-names = "vcc", "vdd";
+    };
+
+This represents a device with two IIO inputs, named "vcc" and "vdd".
+The vcc channel is connected to output 1 of the &adc device, and the
+vdd channel is connected to output 0 of the &ref device.
+
+==Example==
+
+	adc: max1139@35 {
+		compatible = "maxim,max1139";
+		reg = <0x35>;
+		#io-channel-cells = <1>;
+	};
+
+	...
+
+	iio_hwmon {
+		compatible = "iio-hwmon";
+		io-channels = <&adc 0>, <&adc 1>, <&adc 2>,
+			<&adc 3>, <&adc 4>, <&adc 5>,
+			<&adc 6>, <&adc 7>, <&adc 8>,
+			<&adc 9>, <&adc 10>, <&adc 11>;
+		io-channel-names = "vcc", "vdd", "vref", "1.2V";
+	};
diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
index b289915..d48f2a8 100644
--- a/drivers/iio/inkern.c
+++ b/drivers/iio/inkern.c
@@ -10,6 +10,7 @@
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 
 #include <linux/iio/iio.h>
 #include "iio_core.h"
@@ -92,6 +93,179 @@ static const struct iio_chan_spec
 	return chan;
 }
 
+#ifdef CONFIG_OF
+
+static int iio_dev_node_match(struct device *dev, void *data)
+{
+	return !strcmp(dev->type->name, "iio_device") && dev->of_node == data;
+}
+
+static struct iio_channel *of_iio_channel_get(struct device_node *np, int index)
+{
+	struct iio_channel *channel;
+	struct device *idev;
+	struct iio_dev *indio_dev;
+	int err;
+	struct of_phandle_args iiospec;
+
+	if (index < 0)
+		return ERR_PTR(-EINVAL);
+
+	err = of_parse_phandle_with_args(np, "io-channels",
+					 "#io-channel-cells",
+					 index, &iiospec);
+	if (err)
+		return ERR_PTR(err);
+
+	idev = bus_find_device(&iio_bus_type, NULL, iiospec.np,
+			       iio_dev_node_match);
+	of_node_put(iiospec.np);
+	if (idev == NULL)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	indio_dev = dev_to_iio_dev(idev);
+
+	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
+	if (channel == NULL) {
+		err = -ENOMEM;
+		goto err_no_mem;
+	}
+
+	channel->indio_dev = indio_dev;
+	index = iiospec.args_count ? iiospec.args[0] : 0;
+	if (index >= indio_dev->num_channels) {
+		err = -EINVAL;
+		goto err_no_channel;
+	}
+	channel->channel = &indio_dev->channels[index];
+
+	return channel;
+
+err_no_channel:
+	kfree(channel);
+err_no_mem:
+	iio_device_put(indio_dev);
+	return ERR_PTR(err);
+}
+
+static struct iio_channel *of_iio_channel_get_by_name(struct device_node *np,
+						      const char *name)
+{
+	struct iio_channel *chan = ERR_PTR(-ENOENT);
+
+	/* Walk up the tree of devices looking for a matching iio channel */
+	while (np) {
+		int index = 0;
+
+		/*
+		 * For named iio channels, first look up the name in the
+		 * "io-channel-names" property.  If it cannot be found, the
+		 * index will be an error code, and of_iio_channel_get()
+		 * will fail.
+		 */
+		if (name)
+			index = of_property_match_string(np, "io-channel-names",
+							 name);
+		chan = of_iio_channel_get(np, index);
+		if (!IS_ERR(chan))
+			break;
+		else if (name && index >= 0) {
+			pr_err("ERROR: could not get IIO channel %s:%s(%i)\n",
+				np->full_name, name ? name : "", index);
+			return chan;
+		}
+
+		/*
+		 * No matching IIO channel found on this node.
+		 * If the parent node has a "io-channel-ranges" property,
+		 * then we can try one of its channels.
+		 */
+		np = np->parent;
+		if (np && !of_get_property(np, "io-channel-ranges", NULL))
+			break;
+	}
+	return chan;
+}
+
+static struct iio_channel *of_iio_channel_get_all(struct device *dev)
+{
+	struct iio_channel *chans;
+	int i, mapind, nummaps = 0;
+	int ret;
+
+	do {
+		ret = of_parse_phandle_with_args(dev->of_node,
+						 "io-channels",
+						 "#io-channel-cells",
+						 nummaps, NULL);
+		if (ret < 0)
+			break;
+	} while (++nummaps);
+
+	if (nummaps == 0)	/* no error, return NULL to search map table */
+		return NULL;
+
+	/* NULL terminated array to save passing size */
+	chans = kzalloc(sizeof(*chans)*(nummaps + 1), GFP_KERNEL);
+	if (chans == NULL) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	/* Search for OF matches */
+	for (mapind = 0; mapind < nummaps; mapind++) {
+		struct device *idev;
+		struct iio_dev *indio_dev;
+		int channel;
+		struct of_phandle_args iiospec;
+
+		ret = of_parse_phandle_with_args(dev->of_node,
+						 "io-channels",
+						 "#io-channel-cells",
+						 mapind, &iiospec);
+		if (ret)
+			goto error_free_chans;
+
+		idev = bus_find_device(&iio_bus_type, NULL, iiospec.np,
+				       iio_dev_node_match);
+		of_node_put(iiospec.np);
+		if (idev == NULL) {
+			ret = -EPROBE_DEFER;
+			goto error_free_chans;
+		}
+		indio_dev = dev_to_iio_dev(idev);
+		channel = iiospec.args_count ? iiospec.args[0] : 0;
+		if (channel >= indio_dev->num_channels) {
+			ret = -EINVAL;
+			goto error_free_chans;
+		}
+		chans[mapind].indio_dev = indio_dev;
+		chans[mapind].channel = &indio_dev->channels[channel];
+	}
+	return chans;
+
+error_free_chans:
+	for (i = 0; i < mapind; i++)
+		iio_device_put(chans[i].indio_dev);
+	kfree(chans);
+error:
+	return ERR_PTR(ret);
+}
+
+#else /* CONFIG_OF */
+
+static inline struct iio_channel *
+of_iio_channel_get_by_name(struct device_node *np, const char *name)
+{
+	return ERR_PTR(-ENOENT);
+}
+
+static inline struct iio_channel *of_iio_channel_get_all(struct device *dev)
+{
+	return NULL;
+}
+
+#endif /* CONFIG_OF */
 
 static struct iio_channel *iio_channel_get_sys(const char *name,
 					       const char *channel_name)
@@ -150,7 +324,14 @@ struct iio_channel *iio_channel_get(struct device *dev,
 				    const char *channel_name)
 {
 	const char *name = dev ? dev_name(dev) : NULL;
+	struct iio_channel *channel;
 
+	if (dev) {
+		channel = of_iio_channel_get_by_name(dev->of_node,
+						     channel_name);
+		if (!IS_ERR(channel))
+			return channel;
+	}
 	return iio_channel_get_sys(name, channel_name);
 }
 EXPORT_SYMBOL_GPL(iio_channel_get);
@@ -173,6 +354,11 @@ struct iio_channel *iio_channel_get_all(struct device *dev)
 
 	if (dev == NULL)
 		return ERR_PTR(-EINVAL);
+
+	chans = of_iio_channel_get_all(dev);
+	if (chans)
+		return chans;
+
 	name = dev_name(dev);
 
 	mutex_lock(&iio_map_list_lock);
-- 
1.7.9.7