[PATCH] of: support an enumerated-bus compatible value

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

From: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>

An "enumerated" bus is one that is not memory-mapped, hence hence
typically has #address-cells=1, and #size-cells=0. Such buses would be
used to group related non-memory-mapped nodes together, often just under
the top-level of the device tree. The ability to group nodes into a non-
memory-mapped subnode of the root is important, since if nodes exist to
describe multiple entities of the same type, the nodes will have the
same name, and hence require a unit address to differentiate them. It
doesn't make sense to assign bogus unit addresses from the CPU's own
address space for this purpose. An example:

	regulators {
		compatible = "enumerated-bus";
		#address-cells = <1>;
		#size-cells = <0>;

		regulator@0 {
			compatible = "regulator-fixed";
			reg = <0>;
		};

		regulator@1 {
			compatible = "regulator-fixed";
			reg = <1>;
		};
	};

Finally, because such buses are not memory-mapped, we avoid creating
any IO/memory resources for the device.

Signed-off-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
---
 drivers/of/platform.c     |   79 ++++++++++++++++++++++++++++++++++----------
 include/linux/of_device.h |    2 +-
 2 files changed, 62 insertions(+), 19 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 3132ea0..3ebefa9 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -25,6 +25,7 @@
 
 const struct of_device_id of_default_bus_match_table[] = {
 	{ .compatible = "simple-bus", },
+	{ .compatible = "enumerated-bus", },
 #ifdef CONFIG_ARM_AMBA
 	{ .compatible = "arm,amba-bus", },
 #endif /* CONFIG_ARM_AMBA */
@@ -67,16 +68,25 @@ EXPORT_SYMBOL(of_find_device_by_node);
 /**
  * of_device_make_bus_id - Use the device node data to assign a unique name
  * @dev: pointer to device structure that is linked to a device tree node
+ * @enumerated: Is the parent bus of the device an "enumerated" bus?
  *
  * This routine will first try using either the dcr-reg or the reg property
  * value to derive a unique name.  As a last resort it will use the node
  * name followed by a unique number.
+ *
+ * An "enumerated" bus is assumed to support #size-cells=0, and not be memory-
+ * mapped. This prevents of_translate_address() from being used on the
+ * device's reg property; performing address translation makes no logical
+ * sense, and fails if #size-cells=0. We use the first component of the reg
+ * property directly to form a unique name in this case; this value is only
+ * local to the bus, rather than typically globally unique.
  */
-void of_device_make_bus_id(struct device *dev)
+void of_device_make_bus_id(struct device *dev, bool enumerated)
 {
 	static atomic_t bus_no_reg_magic;
 	struct device_node *node = dev->of_node;
 	const u32 *reg;
+	const __be32 *addrp;
 	u64 addr;
 	int magic;
 
@@ -105,7 +115,15 @@ void of_device_make_bus_id(struct device *dev)
 	 */
 	reg = of_get_property(node, "reg", NULL);
 	if (reg) {
-		addr = of_translate_address(node, reg);
+		if (enumerated) {
+			addrp = of_get_address(node, 0, NULL, NULL);
+			if (addrp)
+				addr = of_read_number(addrp, 1);
+			else
+				addr = OF_BAD_ADDR;
+		} else {
+			addr = of_translate_address(node, reg);
+		}
 		if (addr != OF_BAD_ADDR) {
 			dev_set_name(dev, "%llx.%s",
 				     (unsigned long long)addr, node->name);
@@ -126,10 +144,12 @@ void of_device_make_bus_id(struct device *dev)
  * @np: device node to assign to device
  * @bus_id: Name to assign to the device.  May be null to use default name.
  * @parent: Parent device.
+ * @enumerated: Is the parent bus of the device an "enumerated" bus?
  */
-struct platform_device *of_device_alloc(struct device_node *np,
-				  const char *bus_id,
-				  struct device *parent)
+struct platform_device *__of_device_alloc(struct device_node *np,
+					  const char *bus_id,
+					  struct device *parent,
+					  bool enumerated)
 {
 	struct platform_device *dev;
 	int rc, i, num_reg = 0, num_irq;
@@ -140,8 +160,9 @@ struct platform_device *of_device_alloc(struct device_node *np,
 		return NULL;
 
 	/* count the io and irq resources */
-	while (of_address_to_resource(np, num_reg, &temp_res) == 0)
-		num_reg++;
+	if (!enumerated)
+		while (of_address_to_resource(np, num_reg, &temp_res) == 0)
+			num_reg++;
 	num_irq = of_irq_count(np);
 
 	/* Populate the resource table */
@@ -170,10 +191,23 @@ struct platform_device *of_device_alloc(struct device_node *np,
 	if (bus_id)
 		dev_set_name(&dev->dev, "%s", bus_id);
 	else
-		of_device_make_bus_id(&dev->dev);
+		of_device_make_bus_id(&dev->dev, enumerated);
 
 	return dev;
 }
+
+/**
+ * of_device_alloc - Allocate and initialize an of_device
+ * @np: device node to assign to device
+ * @bus_id: Name to assign to the device.  May be null to use default name.
+ * @parent: Parent device.
+ */
+struct platform_device *of_device_alloc(struct device_node *np,
+				  const char *bus_id,
+				  struct device *parent)
+{
+	return __of_device_alloc(np, bus_id, parent, false);
+}
 EXPORT_SYMBOL(of_device_alloc);
 
 /**
@@ -190,14 +224,15 @@ struct platform_device *of_platform_device_create_pdata(
 					struct device_node *np,
 					const char *bus_id,
 					void *platform_data,
-					struct device *parent)
+					struct device *parent,
+					bool enumerated)
 {
 	struct platform_device *dev;
 
 	if (!of_device_is_available(np))
 		return NULL;
 
-	dev = of_device_alloc(np, bus_id, parent);
+	dev = __of_device_alloc(np, bus_id, parent, enumerated);
 	if (!dev)
 		return NULL;
 
@@ -234,7 +269,7 @@ struct platform_device *of_platform_device_create(struct device_node *np,
 					    const char *bus_id,
 					    struct device *parent)
 {
-	return of_platform_device_create_pdata(np, bus_id, NULL, parent);
+	return of_platform_device_create_pdata(np, bus_id, NULL, parent, false);
 }
 EXPORT_SYMBOL(of_platform_device_create);
 
@@ -265,7 +300,7 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 	if (bus_id)
 		dev_set_name(&dev->dev, "%s", bus_id);
 	else
-		of_device_make_bus_id(&dev->dev);
+		of_device_make_bus_id(&dev->dev, false);
 
 	/* setup amba-specific device info */
 	dev->dma_mask = ~0;
@@ -342,7 +377,8 @@ static const struct of_dev_auxdata *of_dev_lookup(const struct of_dev_auxdata *l
 static int of_platform_bus_create(struct device_node *bus,
 				  const struct of_device_id *matches,
 				  const struct of_dev_auxdata *lookup,
-				  struct device *parent, bool strict)
+				  struct device *parent, bool strict,
+				  bool enumerated)
 {
 	const struct of_dev_auxdata *auxdata;
 	struct device_node *child;
@@ -369,13 +405,17 @@ static int of_platform_bus_create(struct device_node *bus,
 		return 0;
 	}
 
-	dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
+	dev = of_platform_device_create_pdata(bus, bus_id, platform_data,
+					      parent, enumerated);
 	if (!dev || !of_match_node(matches, bus))
 		return 0;
 
+	enumerated = of_device_is_compatible(bus, "enumerated-bus");
+
 	for_each_child_of_node(bus, child) {
 		pr_debug("   create child: %s\n", child->full_name);
-		rc = of_platform_bus_create(child, matches, lookup, &dev->dev, strict);
+		rc = of_platform_bus_create(child, matches, lookup, &dev->dev,
+					    strict, enumerated);
 		if (rc) {
 			of_node_put(child);
 			break;
@@ -409,11 +449,13 @@ int of_platform_bus_probe(struct device_node *root,
 
 	/* Do a self check of bus type, if there's a match, create children */
 	if (of_match_node(matches, root)) {
-		rc = of_platform_bus_create(root, matches, NULL, parent, false);
+		rc = of_platform_bus_create(root, matches, NULL, parent, false,
+					    false);
 	} else for_each_child_of_node(root, child) {
 		if (!of_match_node(matches, child))
 			continue;
-		rc = of_platform_bus_create(child, matches, NULL, parent, false);
+		rc = of_platform_bus_create(child, matches, NULL, parent, false,
+					    false);
 		if (rc)
 			break;
 	}
@@ -454,7 +496,8 @@ int of_platform_populate(struct device_node *root,
 		return -EINVAL;
 
 	for_each_child_of_node(root, child) {
-		rc = of_platform_bus_create(child, matches, lookup, parent, true);
+		rc = of_platform_bus_create(child, matches, lookup, parent,
+					    true, false);
 		if (rc)
 			break;
 	}
diff --git a/include/linux/of_device.h b/include/linux/of_device.h
index 901b743..630972e 100644
--- a/include/linux/of_device.h
+++ b/include/linux/of_device.h
@@ -12,7 +12,7 @@ struct device;
 
 extern const struct of_device_id *of_match_device(
 	const struct of_device_id *matches, const struct device *dev);
-extern void of_device_make_bus_id(struct device *dev);
+extern void of_device_make_bus_id(struct device *dev, bool enumerated);
 
 /**
  * of_driver_match_device - Tell if a driver's of_match_table matches a device.
-- 
1.7.0.4