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e2138cf1e6
These macros have AFAICT never been used at all. It's also far from clear what purpose it could serve - for one thing, what _type would one pass, other than void perhaps? The example using "struct my_sub_cmd" seems misplaced, as how could one know that the first linker list consists of those, and moreover, how would one know how many there are? The linker list concept is fragile enough on its own, there is no need to have unused functionality lying around that may or may not bitrot and certainly will confuse readers of linker_lists.h. Signed-off-by: Rasmus Villemoes <ravi@prevas.dk> Reviewed-by: Simon Glass <sjg@chromium.org>
294 lines
9.2 KiB
C
294 lines
9.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* include/linker_lists.h
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*
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* Implementation of linker-generated arrays
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*
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* Copyright (C) 2012 Marek Vasut <marex@denx.de>
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*/
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#ifndef __LINKER_LISTS_H__
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#define __LINKER_LISTS_H__
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#include <linux/compiler.h>
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/*
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* There is no use in including this from ASM files.
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* So just don't define anything when included from ASM.
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*/
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#if !defined(__ASSEMBLY__)
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/**
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* llsym() - Access a linker-generated array entry
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* @_type: Data type of the entry
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* @_name: Name of the entry
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* @_list: name of the list. Should contain only characters allowed
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* in a C variable name!
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*/
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#define llsym(_type, _name, _list) \
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((_type *)&_u_boot_list_2_##_list##_2_##_name)
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/**
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* ll_entry_declare() - Declare linker-generated array entry
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* @_type: Data type of the entry
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* @_name: Name of the entry
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* @_list: name of the list. Should contain only characters allowed
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* in a C variable name!
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*
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* This macro declares a variable that is placed into a linker-generated
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* array. This is a basic building block for more advanced use of linker-
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* generated arrays. The user is expected to build their own macro wrapper
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* around this one.
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*
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* A variable declared using this macro must be compile-time initialized.
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*
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* Special precaution must be made when using this macro:
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*
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* 1) The _type must not contain the "static" keyword, otherwise the
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* entry is generated and can be iterated but is listed in the map
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* file and cannot be retrieved by name.
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*
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* 2) In case a section is declared that contains some array elements AND
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* a subsection of this section is declared and contains some elements,
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* it is imperative that the elements are of the same type.
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*
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* 3) In case an outer section is declared that contains some array elements
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* AND an inner subsection of this section is declared and contains some
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* elements, then when traversing the outer section, even the elements of
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* the inner sections are present in the array.
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*
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* Example:
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*
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* ::
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*
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* ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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* .x = 3,
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* .y = 4,
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* };
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*/
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#define ll_entry_declare(_type, _name, _list) \
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_type _u_boot_list_2_##_list##_2_##_name __aligned(4) \
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__attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_2_"#_name)
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/**
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* ll_entry_declare_list() - Declare a list of link-generated array entries
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* @_type: Data type of each entry
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* @_name: Name of the entry
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* @_list: name of the list. Should contain only characters allowed
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* in a C variable name!
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*
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* This is like ll_entry_declare() but creates multiple entries. It should
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* be assigned to an array.
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*
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* ::
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*
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* ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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* { .x = 3, .y = 4 },
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* { .x = 8, .y = 2 },
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* { .x = 1, .y = 7 }
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* };
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*/
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#define ll_entry_declare_list(_type, _name, _list) \
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_type _u_boot_list_2_##_list##_2_##_name[] __aligned(4) \
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__attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_2_"#_name)
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/*
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* We need a 0-byte-size type for iterator symbols, and the compiler
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* does not allow defining objects of C type 'void'. Using an empty
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* struct is allowed by the compiler, but causes gcc versions 4.4 and
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* below to complain about aliasing. Therefore we use the next best
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* thing: zero-sized arrays, which are both 0-byte-size and exempt from
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* aliasing warnings.
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*/
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/**
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* ll_entry_start() - Point to first entry of linker-generated array
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* @_type: Data type of the entry
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* @_list: Name of the list in which this entry is placed
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*
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* This function returns ``(_type *)`` pointer to the very first entry of a
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* linker-generated array placed into subsection of __u_boot_list section
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* specified by _list argument.
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*
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* Since this macro defines an array start symbol, its leftmost index
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* must be 2 and its rightmost index must be 1.
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*
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* Example:
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*
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* ::
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*
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* struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
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*/
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#define ll_entry_start(_type, _list) \
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({ \
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static char start[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \
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__attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_1"); \
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_type * tmp = (_type *)&start; \
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asm("":"+r"(tmp)); \
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tmp; \
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})
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/**
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* ll_entry_end() - Point after last entry of linker-generated array
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* @_type: Data type of the entry
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* @_list: Name of the list in which this entry is placed
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* (with underscores instead of dots)
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*
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* This function returns ``(_type *)`` pointer after the very last entry of
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* a linker-generated array placed into subsection of __u_boot_list
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* section specified by _list argument.
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*
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* Since this macro defines an array end symbol, its leftmost index
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* must be 2 and its rightmost index must be 3.
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*
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* Example:
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*
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* ::
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*
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* struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub);
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*/
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#define ll_entry_end(_type, _list) \
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({ \
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static char end[0] __aligned(4) __attribute__((unused)) \
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__section("__u_boot_list_2_"#_list"_3"); \
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_type * tmp = (_type *)&end; \
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asm("":"+r"(tmp)); \
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tmp; \
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})
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/**
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* ll_entry_count() - Return the number of elements in linker-generated array
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* @_type: Data type of the entry
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* @_list: Name of the list of which the number of elements is computed
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*
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* This function returns the number of elements of a linker-generated array
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* placed into subsection of __u_boot_list section specified by _list
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* argument. The result is of an unsigned int type.
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*
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* Example:
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*
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* ::
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*
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* int i;
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* const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub);
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* struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
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* for (i = 0; i < count; i++, msc++)
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* printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y);
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*/
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#define ll_entry_count(_type, _list) \
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({ \
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_type *start = ll_entry_start(_type, _list); \
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_type *end = ll_entry_end(_type, _list); \
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unsigned int _ll_result = end - start; \
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_ll_result; \
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})
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/**
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* Declares a symbol that points to the start/end of the list.
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*
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* @_sym: Arbitrary name for the symbol (to use later in the file)
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* @_type: Data type of the entry
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* @_list: Name of the list in which this entry is placed
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*
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* The name of the (new) symbol is arbitrary and can be anything that is not
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* already declared in the file where it appears. It is provided in _sym and
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* can then be used (later in the same file) within a data structure.
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* The _type and _list arguments must match those passed to ll_entry_start/end()
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*
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* Example:
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*
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* Here we want to record the start of each sub-command in a list. We have two
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* sub-commands, 'bob' and 'mary'.
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*
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* In bob.c::
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*
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* ll_entry_declare(struct my_sub_cmd, bob_cmd, cmd_sub) = {...};
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*
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* In mary.c::
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*
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* ll_entry_declare(struct my_sub_cmd, mary_cmd, cmd_sub) = {...};
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*
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* In a different file where we want a list the start of all sub-commands.
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* It is not possible to use ll_entry_start() in a data structure, due to its
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* use of code inside expressions - ({ ... }) - so this fails to compile:
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*
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* In sub_cmds.c::
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*
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* struct cmd_sub *my_list[] = {
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* ll_entry_start(cmd_sub, bob),
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* ll_entry_start(cmd_sub, bob),
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* };
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*
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* Instead, we can use::
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*
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* ll_start_decl(bob, struct my_sub_cmd, cmd_sub);
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* ll_start_decl(mary, struct my_sub_cmd, cmd_sub);
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*
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* struct cmd_sub *my_list[] = {
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* bob,
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* mary,
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* };
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*
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* So 'bob' is declared as symbol, a struct my_list * which points to the
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* start of the bob sub-commands. It is then used in my_list[]
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*/
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#define ll_start_decl(_sym, _type, _list) \
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static _type _sym[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \
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__maybe_unused __section("__u_boot_list_2_" #_list "_1")
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#define ll_end_decl(_sym, _type, _list) \
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static _type _sym[0] __aligned(CONFIG_LINKER_LIST_ALIGN) \
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__maybe_unused __section("__u_boot_list_2_" #_list "_3")
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/**
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* ll_entry_get() - Retrieve entry from linker-generated array by name
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* @_type: Data type of the entry
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* @_name: Name of the entry
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* @_list: Name of the list in which this entry is placed
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*
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* This function returns a pointer to a particular entry in linker-generated
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* array identified by the subsection of u_boot_list where the entry resides
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* and it's name.
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*
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* Example:
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*
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* ::
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*
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* ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
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* .x = 3,
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* .y = 4,
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* };
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* ...
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* struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub);
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*/
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#define ll_entry_get(_type, _name, _list) \
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({ \
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extern _type _u_boot_list_2_##_list##_2_##_name; \
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_type *_ll_result = \
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&_u_boot_list_2_##_list##_2_##_name; \
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_ll_result; \
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})
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/**
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* ll_entry_ref() - Get a reference to a linker-generated array entry
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*
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* Once an extern ll_entry_declare() has been used to declare the reference,
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* this macro allows the entry to be accessed.
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*
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* This is like ll_entry_get(), but without the extra code, so it is suitable
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* for putting into data structures.
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*
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* @_type: C type of the list entry, e.g. 'struct foo'
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* @_name: name of the entry
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* @_list: name of the list
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*/
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#define ll_entry_ref(_type, _name, _list) \
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((_type *)&_u_boot_list_2_##_list##_2_##_name)
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#endif /* __ASSEMBLY__ */
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#endif /* __LINKER_LISTS_H__ */
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