linker list是利用lds 描述符实现同类型数据连续排布的一种机制。
下面是uboot里面的应用说明
lds文件里面需要增加section描述：
. = ALIGN(4);
.u_boot_list : {
KEEP(*(SORT(.u_boot_list*)));
}
linker_list.h:
/* SPDX-License-Identifier: GPL-2.0+ */
/*
* include/linker_lists.h
*
* Implementation of linker-generated arrays
*
* Copyright (C) 2012 Marek Vasut <marex@denx.de>
*/
#ifndef __LINKER_LISTS_H__
#define __LINKER_LISTS_H__
#include <linux/compiler.h>
/*
* There is no use in including this from ASM files.
* So just don't define anything when included from ASM.
*/
#if !defined(__ASSEMBLY__)
/**
* llsym() - Access a linker-generated array entry
* @_type: Data type of the entry
* @_name: Name of the entry
* @_list: name of the list. Should contain only characters allowed
* in a C variable name!
*/
#define llsym(_type, _name, _list) \
((_type *)&_u_boot_list_2_##_list##_2_##_name)
/**
* ll_entry_declare() - Declare linker-generated array entry
* @_type: Data type of the entry
* @_name: Name of the entry
* @_list: name of the list. Should contain only characters allowed
* in a C variable name!
*
* This macro declares a variable that is placed into a linker-generated
* array. This is a basic building block for more advanced use of linker-
* generated arrays. The user is expected to build their own macro wrapper
* around this one.
*
* A variable declared using this macro must be compile-time initialized.
*
* Special precaution must be made when using this macro:
*
* 1) The _type must not contain the "static" keyword, otherwise the
* entry is generated and can be iterated but is listed in the map
* file and cannot be retrieved by name.
*
* 2) In case a section is declared that contains some array elements AND
* a subsection of this section is declared and contains some elements,
* it is imperative that the elements are of the same type.
*
* 3) In case an outer section is declared that contains some array elements
* AND an inner subsection of this section is declared and contains some
* elements, then when traversing the outer section, even the elements of
* the inner sections are present in the array.
*
* Example:
*
* ::
*
* ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
* .x = 3,
* .y = 4,
* };
*/
#define ll_entry_declare(_type, _name, _list) \
_type _u_boot_list_2_##_list##_2_##_name __aligned(4) \
__attribute__((unused, \
section(".u_boot_list_2_"#_list"_2_"#_name)))
/**
* ll_entry_declare_list() - Declare a list of link-generated array entries
* @_type: Data type of each entry
* @_name: Name of the entry
* @_list: name of the list. Should contain only characters allowed
* in a C variable name!
*
* This is like ll_entry_declare() but creates multiple entries. It should
* be assigned to an array.
*
* ::
*
* ll_entry_declare_list(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
* { .x = 3, .y = 4 },
* { .x = 8, .y = 2 },
* { .x = 1, .y = 7 }
* };
*/
#define ll_entry_declare_list(_type, _name, _list) \
_type _u_boot_list_2_##_list##_2_##_name[] __aligned(4) \
__attribute__((unused, \
section(".u_boot_list_2_"#_list"_2_"#_name)))
/*
* We need a 0-byte-size type for iterator symbols, and the compiler
* does not allow defining objects of C type 'void'. Using an empty
* struct is allowed by the compiler, but causes gcc versions 4.4 and
* below to complain about aliasing. Therefore we use the next best
* thing: zero-sized arrays, which are both 0-byte-size and exempt from
* aliasing warnings.
*/
/**
* ll_entry_start() - Point to first entry of linker-generated array
* @_type: Data type of the entry
* @_list: Name of the list in which this entry is placed
*
* This function returns ``(_type *)`` pointer to the very first entry of a
* linker-generated array placed into subsection of .u_boot_list section
* specified by _list argument.
*
* Since this macro defines an array start symbol, its leftmost index
* must be 2 and its rightmost index must be 1.
*
* Example:
*
* ::
*
* struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
*/
#define ll_entry_start(_type, _list) \
({ \
static char start[0] __aligned(4) __attribute__((unused, \
section(".u_boot_list_2_"#_list"_1"))); \
(_type *)&start; \
})
/**
* ll_entry_end() - Point after last entry of linker-generated array
* @_type: Data type of the entry
* @_list: Name of the list in which this entry is placed
* (with underscores instead of dots)
*
* This function returns ``(_type *)`` pointer after the very last entry of
* a linker-generated array placed into subsection of .u_boot_list
* section specified by _list argument.
*
* Since this macro defines an array end symbol, its leftmost index
* must be 2 and its rightmost index must be 3.
*
* Example:
*
* ::
*
* struct my_sub_cmd *msc = ll_entry_end(struct my_sub_cmd, cmd_sub);
*/
#define ll_entry_end(_type, _list) \
({ \
static char end[0] __aligned(4) __attribute__((unused, \
section(".u_boot_list_2_"#_list"_3"))); \
(_type *)&end; \
})
/**
* ll_entry_count() - Return the number of elements in linker-generated array
* @_type: Data type of the entry
* @_list: Name of the list of which the number of elements is computed
*
* This function returns the number of elements of a linker-generated array
* placed into subsection of .u_boot_list section specified by _list
* argument. The result is of an unsigned int type.
*
* Example:
*
* ::
*
* int i;
* const unsigned int count = ll_entry_count(struct my_sub_cmd, cmd_sub);
* struct my_sub_cmd *msc = ll_entry_start(struct my_sub_cmd, cmd_sub);
* for (i = 0; i < count; i++, msc++)
* printf("Entry %i, x=%i y=%i\n", i, msc->x, msc->y);
*/
#define ll_entry_count(_type, _list) \
({ \
_type *start = ll_entry_start(_type, _list); \
_type *end = ll_entry_end(_type, _list); \
unsigned int _ll_result = end - start; \
_ll_result; \
})
/**
* ll_entry_get() - Retrieve entry from linker-generated array by name
* @_type: Data type of the entry
* @_name: Name of the entry
* @_list: Name of the list in which this entry is placed
*
* This function returns a pointer to a particular entry in linker-generated
* array identified by the subsection of u_boot_list where the entry resides
* and it's name.
*
* Example:
*
* ::
*
* ll_entry_declare(struct my_sub_cmd, my_sub_cmd, cmd_sub) = {
* .x = 3,
* .y = 4,
* };
* ...
* struct my_sub_cmd *c = ll_entry_get(struct my_sub_cmd, my_sub_cmd, cmd_sub);
*/
#define ll_entry_get(_type, _name, _list) \
({ \
extern _type _u_boot_list_2_##_list##_2_##_name; \
_type *_ll_result = \
&_u_boot_list_2_##_list##_2_##_name; \
_ll_result; \
})
/**
* ll_start() - Point to first entry of first linker-generated array
* @_type: Data type of the entry
*
* This function returns ``(_type *)`` pointer to the very first entry of
* the very first linker-generated array.
*
* Since this macro defines the start of the linker-generated arrays,
* its leftmost index must be 1.
*
* Example:
*
* ::
*
* struct my_sub_cmd *msc = ll_start(struct my_sub_cmd);
*/
#define ll_start(_type) \
({ \
static char start[0] __aligned(4) __attribute__((unused, \
section(".u_boot_list_1"))); \
(_type *)&start; \
})
/**
* ll_end() - Point after last entry of last linker-generated array
* @_type: Data type of the entry
*
* This function returns ``(_type *)`` pointer after the very last entry of
* the very last linker-generated array.
*
* Since this macro defines the end of the linker-generated arrays,
* its leftmost index must be 3.
*
* Example:
*
* ::
*
* struct my_sub_cmd *msc = ll_end(struct my_sub_cmd);
*/
#define ll_end(_type) \
({ \
static char end[0] __aligned(4) __attribute__((unused, \
section(".u_boot_list_3"))); \
(_type *)&end; \
})
#endif /* __ASSEMBLY__ */
#endif /* __LINKER_LISTS_H__ */
ll_entry_declare_list 和ll_entry_declare差别是前者是数组声明，一次可以声明多个条目，后者只声明（定义）一个条目。
ll_entry_start(_type, _list) 获取该类型列表首个条目地址
ll_entry_get(_type, _name, _list) 根据名字 返回条目地址
ll_entry_count(_type, _list) 返回该类型条目数
使用实例
参考driver的定义：
struct driver {
char *name;
enum uclass_id id;
const struct udevice_id *of_match;
int (*bind)(struct udevice *dev);
int (*probe)(struct udevice *dev);
int (*remove)(struct udevice *dev);
int (*unbind)(struct udevice *dev);
int (*ofdata_to_platdata)(struct udevice *dev);
int (*child_post_bind)(struct udevice *dev);
int (*child_pre_probe)(struct udevice *dev);
int (*child_post_remove)(struct udevice *dev);
int priv_auto_alloc_size;
int platdata_auto_alloc_size;
int per_child_auto_alloc_size;
int per_child_platdata_auto_alloc_size;
const void *ops; /* driver-specific operations */
uint32_t flags;
};
/* Declare a new U-Boot driver */
#define U_BOOT_DRIVER(__name) \
ll_entry_declare(struct driver, __name, driver)
usb hub driver
U_BOOT_DRIVER(usb_generic_hub) = {
.name = "usb_hub",
.id = UCLASS_USB_HUB,
.of_match = usb_hub_ids,
.flags = DM_FLAG_ALLOC_PRIV_DMA,
};