Driver core: Unified device properties interface for platform firmware

Add a uniform interface by which device drivers can request device
properties from the platform firmware by providing a property name
and the corresponding data type.  The purpose of it is to help to
write portable code that won't depend on any particular platform
firmware interface.

The following general helper functions are added:

device_property_present()
device_property_read_u8()
device_property_read_u16()
device_property_read_u32()
device_property_read_u64()
device_property_read_string()
device_property_read_u8_array()
device_property_read_u16_array()
device_property_read_u32_array()
device_property_read_u64_array()
device_property_read_string_array()

The first one allows the caller to check if the given property is
present.  The next 5 of them allow single-valued properties of
various types to be retrieved in a uniform way.  The remaining 5 are
for reading properties with multiple values (arrays of either numbers
or strings).

The interface covers both ACPI and Device Trees.

This change set includes material from Mika Westerberg and Aaron Lu.

Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 186 insertions, 1 deletions

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 6922cd6850a2..53c3fe1aeb29 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -4,7 +4,7 @@ obj-y			:= component.o core.o bus.o dd.o syscore.o \
 			   driver.o class.o platform.o \
 			   cpu.o firmware.o init.o map.o devres.o \
 			   attribute_container.o transport_class.o \
-			   topology.o container.o
+			   topology.o container.o property.o
 obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
 obj-$(CONFIG_DMA_CMA) += dma-contiguous.o
 obj-y			+= power/
diff --git a/drivers/base/property.c b/drivers/base/property.c
new file mode 100644
index 000000000000..6a94ef6e83c9
--- /dev/null
+++ b/drivers/base/property.c
@@ -0,0 +1,185 @@
+/*
+ * property.c - Unified device property interface.
+ *
+ * Copyright (C) 2014, Intel Corporation
+ * Authors: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+ *          Mika Westerberg <mika.westerberg@linux.intel.com>
+ *
+ * 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/property.h>
+#include <linux/export.h>
+#include <linux/acpi.h>
+#include <linux/of.h>
+
+/**
+ * device_property_present - check if a property of a device is present
+ * @dev: Device whose property is being checked
+ * @propname: Name of the property
+ *
+ * Check if property @propname is present in the device firmware description.
+ */
+bool device_property_present(struct device *dev, const char *propname)
+{
+	if (IS_ENABLED(CONFIG_OF) && dev->of_node)
+		return of_property_read_bool(dev->of_node, propname);
+
+	return !acpi_dev_prop_get(ACPI_COMPANION(dev), propname, NULL);
+}
+EXPORT_SYMBOL_GPL(device_property_present);
+
+#define OF_DEV_PROP_READ_ARRAY(node, propname, type, val, nval) \
+	(val) ? of_property_read_##type##_array((node), (propname), (val), (nval)) \
+	      : of_property_count_elems_of_size((node), (propname), sizeof(type))
+
+#define DEV_PROP_READ_ARRAY(_dev_, _propname_, _type_, _proptype_, _val_, _nval_) \
+	IS_ENABLED(CONFIG_OF) && _dev_->of_node ? \
+		(OF_DEV_PROP_READ_ARRAY(_dev_->of_node, _propname_, _type_, \
+					_val_, _nval_)) : \
+		acpi_dev_prop_read(ACPI_COMPANION(_dev_), _propname_, \
+				   _proptype_, _val_, _nval_)
+
+/**
+ * device_property_read_u8_array - return a u8 array property of a device
+ * @dev: Device to get the property of
+ * @propname: Name of the property
+ * @val: The values are stored here
+ * @nval: Size of the @val array
+ *
+ * Function reads an array of u8 properties with @propname from the device
+ * firmware description and stores them to @val if found.
+ *
+ * Return: %0 if the property was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO if the property is not an array of numbers,
+ *	   %-EOVERFLOW if the size of the property is not as expected.
+ */
+int device_property_read_u8_array(struct device *dev, const char *propname,
+				  u8 *val, size_t nval)
+{
+	return DEV_PROP_READ_ARRAY(dev, propname, u8, DEV_PROP_U8, val, nval);
+}
+EXPORT_SYMBOL_GPL(device_property_read_u8_array);
+
+/**
+ * device_property_read_u16_array - return a u16 array property of a device
+ * @dev: Device to get the property of
+ * @propname: Name of the property
+ * @val: The values are stored here
+ * @nval: Size of the @val array
+ *
+ * Function reads an array of u16 properties with @propname from the device
+ * firmware description and stores them to @val if found.
+ *
+ * Return: %0 if the property was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO if the property is not an array of numbers,
+ *	   %-EOVERFLOW if the size of the property is not as expected.
+ */
+int device_property_read_u16_array(struct device *dev, const char *propname,
+				   u16 *val, size_t nval)
+{
+	return DEV_PROP_READ_ARRAY(dev, propname, u16, DEV_PROP_U16, val, nval);
+}
+EXPORT_SYMBOL_GPL(device_property_read_u16_array);
+
+/**
+ * device_property_read_u32_array - return a u32 array property of a device
+ * @dev: Device to get the property of
+ * @propname: Name of the property
+ * @val: The values are stored here
+ * @nval: Size of the @val array
+ *
+ * Function reads an array of u32 properties with @propname from the device
+ * firmware description and stores them to @val if found.
+ *
+ * Return: %0 if the property was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO if the property is not an array of numbers,
+ *	   %-EOVERFLOW if the size of the property is not as expected.
+ */
+int device_property_read_u32_array(struct device *dev, const char *propname,
+				   u32 *val, size_t nval)
+{
+	return DEV_PROP_READ_ARRAY(dev, propname, u32, DEV_PROP_U32, val, nval);
+}
+EXPORT_SYMBOL_GPL(device_property_read_u32_array);
+
+/**
+ * device_property_read_u64_array - return a u64 array property of a device
+ * @dev: Device to get the property of
+ * @propname: Name of the property
+ * @val: The values are stored here
+ * @nval: Size of the @val array
+ *
+ * Function reads an array of u64 properties with @propname from the device
+ * firmware description and stores them to @val if found.
+ *
+ * Return: %0 if the property was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO if the property is not an array of numbers,
+ *	   %-EOVERFLOW if the size of the property is not as expected.
+ */
+int device_property_read_u64_array(struct device *dev, const char *propname,
+				   u64 *val, size_t nval)
+{
+	return DEV_PROP_READ_ARRAY(dev, propname, u64, DEV_PROP_U64, val, nval);
+}
+EXPORT_SYMBOL_GPL(device_property_read_u64_array);
+
+/**
+ * device_property_read_string_array - return a string array property of device
+ * @dev: Device to get the property of
+ * @propname: Name of the property
+ * @val: The values are stored here
+ * @nval: Size of the @val array
+ *
+ * Function reads an array of string properties with @propname from the device
+ * firmware description and stores them to @val if found.
+ *
+ * Return: %0 if the property was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO or %-EILSEQ if the property is not an array of strings,
+ *	   %-EOVERFLOW if the size of the property is not as expected.
+ */
+int device_property_read_string_array(struct device *dev, const char *propname,
+				      const char **val, size_t nval)
+{
+	return IS_ENABLED(CONFIG_OF) && dev->of_node ?
+		of_property_read_string_array(dev->of_node, propname, val, nval) :
+		acpi_dev_prop_read(ACPI_COMPANION(dev), propname,
+				   DEV_PROP_STRING, val, nval);
+}
+EXPORT_SYMBOL_GPL(device_property_read_string_array);
+
+/**
+ * device_property_read_string - return a string property of a device
+ * @dev: Device to get the property of
+ * @propname: Name of the property
+ * @val: The value is stored here
+ *
+ * Function reads property @propname from the device firmware description and
+ * stores the value into @val if found. The value is checked to be a string.
+ *
+ * Return: %0 if the property was found (success),
+ *	   %-EINVAL if given arguments are not valid,
+ *	   %-ENODATA if the property does not have a value,
+ *	   %-EPROTO or %-EILSEQ if the property type is not a string.
+ */
+int device_property_read_string(struct device *dev, const char *propname,
+				const char **val)
+{
+	return IS_ENABLED(CONFIG_OF) && dev->of_node ?
+		of_property_read_string(dev->of_node, propname, val) :
+		acpi_dev_prop_read(ACPI_COMPANION(dev), propname,
+				   DEV_PROP_STRING, val, 1);
+}
+EXPORT_SYMBOL_GPL(device_property_read_string);