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![Andy Shevchenko](/assets/img/avatar_default.png)
Commit 318a197182
(device property: refactor built-in properties
support) went way too far and brought a union aliasing. Partially
revert it here to get rid of union aliasing.
Note, all Apple properties are considered as u8 arrays. To get a value
of any of them the caller must use device_property_read_u8_array().
What's union aliasing?
~~~~~~~~~~~~~~~~~~~~~~
The C99 standard in section 6.2.5 paragraph 20 defines union type as
"an overlapping nonempty set of member objects". It also states in
section 6.7.2.1 paragraph 14 that "the value of at most one of the
members can be stored in a union object at any time'.
Union aliasing is a type punning mechanism using union members to store
as one type and read back as another.
Why it's not good?
~~~~~~~~~~~~~~~~~~
Section 6.2.6.1 paragraph 6 says that a union object may not be a trap
representation, although its member objects may be.
Meanwhile annex J.1 says that "the value of a union member other than
the last one stored into" is unspecified [removed in C11].
In TC3, a footnote is added which specifies that accessing a member of a
union other than the last one stored causes "the object representation"
to be re-interpreted in the new type and specifically refers to this as
"type punning". This conflicts to some degree with Annex J.1.
While it's working in Linux with GCC, the use of union members to do
type punning is not clear area in the C standard and might lead to
unspecified behaviour.
More information is available in this [1] blog post.
[1]: https://davmac.wordpress.com/2010/02/26/c99-revisited/
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
314 lines
10 KiB
C
314 lines
10 KiB
C
/*
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* property.h - Unified device property interface.
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*
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* Copyright (C) 2014, Intel Corporation
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* Authors: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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* Mika Westerberg <mika.westerberg@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef _LINUX_PROPERTY_H_
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#define _LINUX_PROPERTY_H_
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#include <linux/fwnode.h>
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#include <linux/types.h>
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struct device;
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enum dev_prop_type {
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DEV_PROP_U8,
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DEV_PROP_U16,
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DEV_PROP_U32,
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DEV_PROP_U64,
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DEV_PROP_STRING,
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DEV_PROP_MAX,
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};
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enum dev_dma_attr {
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DEV_DMA_NOT_SUPPORTED,
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DEV_DMA_NON_COHERENT,
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DEV_DMA_COHERENT,
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};
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struct fwnode_handle *dev_fwnode(struct device *dev);
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bool device_property_present(struct device *dev, const char *propname);
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int device_property_read_u8_array(struct device *dev, const char *propname,
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u8 *val, size_t nval);
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int device_property_read_u16_array(struct device *dev, const char *propname,
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u16 *val, size_t nval);
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int device_property_read_u32_array(struct device *dev, const char *propname,
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u32 *val, size_t nval);
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int device_property_read_u64_array(struct device *dev, const char *propname,
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u64 *val, size_t nval);
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int device_property_read_string_array(struct device *dev, const char *propname,
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const char **val, size_t nval);
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int device_property_read_string(struct device *dev, const char *propname,
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const char **val);
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int device_property_match_string(struct device *dev,
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const char *propname, const char *string);
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bool fwnode_device_is_available(const struct fwnode_handle *fwnode);
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bool fwnode_property_present(const struct fwnode_handle *fwnode,
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const char *propname);
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int fwnode_property_read_u8_array(const struct fwnode_handle *fwnode,
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const char *propname, u8 *val,
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size_t nval);
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int fwnode_property_read_u16_array(const struct fwnode_handle *fwnode,
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const char *propname, u16 *val,
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size_t nval);
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int fwnode_property_read_u32_array(const struct fwnode_handle *fwnode,
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const char *propname, u32 *val,
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size_t nval);
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int fwnode_property_read_u64_array(const struct fwnode_handle *fwnode,
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const char *propname, u64 *val,
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size_t nval);
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int fwnode_property_read_string_array(const struct fwnode_handle *fwnode,
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const char *propname, const char **val,
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size_t nval);
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int fwnode_property_read_string(const struct fwnode_handle *fwnode,
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const char *propname, const char **val);
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int fwnode_property_match_string(const struct fwnode_handle *fwnode,
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const char *propname, const char *string);
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int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
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const char *prop, const char *nargs_prop,
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unsigned int nargs, unsigned int index,
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struct fwnode_reference_args *args);
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struct fwnode_handle *fwnode_get_parent(const struct fwnode_handle *fwnode);
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struct fwnode_handle *fwnode_get_next_parent(
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struct fwnode_handle *fwnode);
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struct fwnode_handle *fwnode_get_next_child_node(
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const struct fwnode_handle *fwnode, struct fwnode_handle *child);
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struct fwnode_handle *fwnode_get_next_available_child_node(
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const struct fwnode_handle *fwnode, struct fwnode_handle *child);
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#define fwnode_for_each_child_node(fwnode, child) \
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for (child = fwnode_get_next_child_node(fwnode, NULL); child; \
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child = fwnode_get_next_child_node(fwnode, child))
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#define fwnode_for_each_available_child_node(fwnode, child) \
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for (child = fwnode_get_next_available_child_node(fwnode, NULL); child;\
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child = fwnode_get_next_available_child_node(fwnode, child))
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struct fwnode_handle *device_get_next_child_node(
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struct device *dev, struct fwnode_handle *child);
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#define device_for_each_child_node(dev, child) \
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for (child = device_get_next_child_node(dev, NULL); child; \
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child = device_get_next_child_node(dev, child))
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struct fwnode_handle *fwnode_get_named_child_node(
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const struct fwnode_handle *fwnode, const char *childname);
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struct fwnode_handle *device_get_named_child_node(struct device *dev,
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const char *childname);
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struct fwnode_handle *fwnode_handle_get(struct fwnode_handle *fwnode);
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void fwnode_handle_put(struct fwnode_handle *fwnode);
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int fwnode_irq_get(struct fwnode_handle *fwnode, unsigned int index);
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unsigned int device_get_child_node_count(struct device *dev);
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static inline bool device_property_read_bool(struct device *dev,
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const char *propname)
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{
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return device_property_present(dev, propname);
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}
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static inline int device_property_read_u8(struct device *dev,
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const char *propname, u8 *val)
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{
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return device_property_read_u8_array(dev, propname, val, 1);
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}
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static inline int device_property_read_u16(struct device *dev,
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const char *propname, u16 *val)
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{
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return device_property_read_u16_array(dev, propname, val, 1);
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}
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static inline int device_property_read_u32(struct device *dev,
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const char *propname, u32 *val)
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{
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return device_property_read_u32_array(dev, propname, val, 1);
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}
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static inline int device_property_read_u64(struct device *dev,
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const char *propname, u64 *val)
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{
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return device_property_read_u64_array(dev, propname, val, 1);
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}
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static inline bool fwnode_property_read_bool(const struct fwnode_handle *fwnode,
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const char *propname)
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{
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return fwnode_property_present(fwnode, propname);
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}
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static inline int fwnode_property_read_u8(const struct fwnode_handle *fwnode,
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const char *propname, u8 *val)
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{
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return fwnode_property_read_u8_array(fwnode, propname, val, 1);
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}
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static inline int fwnode_property_read_u16(const struct fwnode_handle *fwnode,
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const char *propname, u16 *val)
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{
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return fwnode_property_read_u16_array(fwnode, propname, val, 1);
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}
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static inline int fwnode_property_read_u32(const struct fwnode_handle *fwnode,
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const char *propname, u32 *val)
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{
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return fwnode_property_read_u32_array(fwnode, propname, val, 1);
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}
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static inline int fwnode_property_read_u64(const struct fwnode_handle *fwnode,
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const char *propname, u64 *val)
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{
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return fwnode_property_read_u64_array(fwnode, propname, val, 1);
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}
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/**
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* struct property_entry - "Built-in" device property representation.
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* @name: Name of the property.
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* @length: Length of data making up the value.
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* @is_array: True when the property is an array.
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* @type: Type of the data in unions.
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* @pointer: Pointer to the property (an array of items of the given type).
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* @value: Value of the property (when it is a single item of the given type).
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*/
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struct property_entry {
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const char *name;
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size_t length;
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bool is_array;
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enum dev_prop_type type;
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union {
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union {
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const u8 *u8_data;
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const u16 *u16_data;
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const u32 *u32_data;
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const u64 *u64_data;
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const char * const *str;
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} pointer;
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union {
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u8 u8_data;
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u16 u16_data;
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u32 u32_data;
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u64 u64_data;
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const char *str;
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} value;
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};
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};
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/*
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* Note: the below four initializers for the anonymous union are carefully
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* crafted to avoid gcc-4.4.4's problems with initialization of anon unions
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* and structs.
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*/
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#define PROPERTY_ENTRY_INTEGER_ARRAY(_name_, _type_, _Type_, _val_) \
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(struct property_entry) { \
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.name = _name_, \
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.length = ARRAY_SIZE(_val_) * sizeof(_type_), \
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.is_array = true, \
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.type = DEV_PROP_##_Type_, \
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{ .pointer = { ._type_##_data = _val_ } }, \
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}
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#define PROPERTY_ENTRY_U8_ARRAY(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER_ARRAY(_name_, u8, U8, _val_)
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#define PROPERTY_ENTRY_U16_ARRAY(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER_ARRAY(_name_, u16, U16, _val_)
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#define PROPERTY_ENTRY_U32_ARRAY(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER_ARRAY(_name_, u32, U32, _val_)
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#define PROPERTY_ENTRY_U64_ARRAY(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER_ARRAY(_name_, u64, U64, _val_)
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#define PROPERTY_ENTRY_STRING_ARRAY(_name_, _val_) \
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(struct property_entry) { \
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.name = _name_, \
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.length = ARRAY_SIZE(_val_) * sizeof(const char *), \
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.is_array = true, \
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.type = DEV_PROP_STRING, \
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{ .pointer = { .str = _val_ } }, \
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}
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#define PROPERTY_ENTRY_INTEGER(_name_, _type_, _Type_, _val_) \
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(struct property_entry) { \
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.name = _name_, \
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.length = sizeof(_type_), \
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.type = DEV_PROP_##_Type_, \
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{ .value = { ._type_##_data = _val_ } }, \
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}
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#define PROPERTY_ENTRY_U8(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER(_name_, u8, U8, _val_)
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#define PROPERTY_ENTRY_U16(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER(_name_, u16, U16, _val_)
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#define PROPERTY_ENTRY_U32(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER(_name_, u32, U32, _val_)
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#define PROPERTY_ENTRY_U64(_name_, _val_) \
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PROPERTY_ENTRY_INTEGER(_name_, u64, U64, _val_)
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#define PROPERTY_ENTRY_STRING(_name_, _val_) \
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(struct property_entry) { \
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.name = _name_, \
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.length = sizeof(_val_), \
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.type = DEV_PROP_STRING, \
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{ .value = { .str = _val_ } }, \
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}
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#define PROPERTY_ENTRY_BOOL(_name_) \
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(struct property_entry) { \
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.name = _name_, \
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}
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struct property_entry *
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property_entries_dup(const struct property_entry *properties);
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void property_entries_free(const struct property_entry *properties);
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int device_add_properties(struct device *dev,
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const struct property_entry *properties);
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void device_remove_properties(struct device *dev);
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bool device_dma_supported(struct device *dev);
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enum dev_dma_attr device_get_dma_attr(struct device *dev);
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const void *device_get_match_data(struct device *dev);
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int device_get_phy_mode(struct device *dev);
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void *device_get_mac_address(struct device *dev, char *addr, int alen);
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int fwnode_get_phy_mode(struct fwnode_handle *fwnode);
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void *fwnode_get_mac_address(struct fwnode_handle *fwnode,
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char *addr, int alen);
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struct fwnode_handle *fwnode_graph_get_next_endpoint(
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const struct fwnode_handle *fwnode, struct fwnode_handle *prev);
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struct fwnode_handle *
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fwnode_graph_get_port_parent(const struct fwnode_handle *fwnode);
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struct fwnode_handle *fwnode_graph_get_remote_port_parent(
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const struct fwnode_handle *fwnode);
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struct fwnode_handle *fwnode_graph_get_remote_port(
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const struct fwnode_handle *fwnode);
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struct fwnode_handle *fwnode_graph_get_remote_endpoint(
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const struct fwnode_handle *fwnode);
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struct fwnode_handle *
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fwnode_graph_get_remote_node(const struct fwnode_handle *fwnode, u32 port,
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u32 endpoint);
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#define fwnode_graph_for_each_endpoint(fwnode, child) \
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for (child = NULL; \
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(child = fwnode_graph_get_next_endpoint(fwnode, child)); )
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int fwnode_graph_parse_endpoint(const struct fwnode_handle *fwnode,
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struct fwnode_endpoint *endpoint);
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#endif /* _LINUX_PROPERTY_H_ */
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