/*
   * include/linker_lists.h
   *
   * Implementation of linker-generated arrays
   *
   * Copyright (C) 2012 Marek Vasut <marex@denx.de>
   *

   * SPDX-License-Identifier:	GPL-2.0+

   */

  #ifndef __LINKER_LISTS_H__
  #define __LINKER_LISTS_H__

  /*
   * There is no use in including this from ASM files, but that happens
   * anyway, e.g. PPC kgdb.S includes command.h which incluse us.
   * So just don't define anything when included from ASM.
   */
  
  #if !defined(__ASSEMBLY__)
  
  /**
   * A linker list is constructed by grouping together linker input
   * sections, each containning one entry of the list. Each input section
   * contains a constant initialized variable which holds the entry's
   * content. Linker list input sections are constructed from the list
   * and entry names, plus a prefix which allows grouping all lists
   * together. Assuming _list and _entry are the list and entry names,
   * then the corresponding input section name is
   *
   *   _u_boot_list + _2_ + @_list + _2_ + @_entry
   *
   * and the C variable name is
   *
   *   .u_boot_list_ + 2_ + @_list + _2_ + @_entry
   *
   * This ensures uniqueness for both input section and C variable name.
   *
   * Note that the names differ only in the first character, "." for the
   * setion and "_" for the variable, so that the linker cannot confuse
   * section and symbol names. From now on, both names will be referred
   * to as
   *
   *   %u_boot_list_ + 2_ + @_list + _2_ + @_entry
   *
   * Entry variables need never be referred to directly.
   *
   * The naming scheme for input sections allows grouping all linker lists
   * into a single linker output section and grouping all entries for a
   * single list.
   *
   * Note the two '_2_' constant components in the names: their presence
   * allows putting a start and end symbols around a list, by mapping
   * these symbols to sections names with components "1" (before) and
   * "3" (after) instead of "2" (within).
   * Start and end symbols for a list can generally be defined as
   *
   *   %u_boot_list_2_ + @_list + _1_...
   *   %u_boot_list_2_ + @_list + _3_...
   *
   * Start and end symbols for the whole of the linker lists area can be
   * defined as
   *
   *   %u_boot_list_1_...
   *   %u_boot_list_3_...
   *
   * Here is an example of the sorted sections which result from a list
   * "array" made up of three entries : "first", "second" and "third",
   * iterated at least once.
   *
   *   .u_boot_list_2_array_1
   *   .u_boot_list_2_array_2_first
   *   .u_boot_list_2_array_2_second
   *   .u_boot_list_2_array_2_third
   *   .u_boot_list_2_array_3
   *
   * If lists must be divided into sublists (e.g. for iterating only on
   * part of a list), one can simply give the list a name of the form
   * 'outer_2_inner', where 'outer' is the global list name and 'inner'
   * is the sub-list name. Iterators for the whole list should use the
   * global list name ("outer"); iterators for only a sub-list should use
   * the full sub-list name ("outer_2_inner").
   *
   *  Here is an example of the sections generated from a global list
   * named "drivers", two sub-lists named "i2c" and "pci", and iterators
   * defined for the whole list and each sub-list:
   *
   *   %u_boot_list_2_drivers_1
   *   %u_boot_list_2_drivers_2_i2c_1
   *   %u_boot_list_2_drivers_2_i2c_2_first
   *   %u_boot_list_2_drivers_2_i2c_2_first
   *   %u_boot_list_2_drivers_2_i2c_2_second
   *   %u_boot_list_2_drivers_2_i2c_2_third
   *   %u_boot_list_2_drivers_2_i2c_3
   *   %u_boot_list_2_drivers_2_pci_1
   *   %u_boot_list_2_drivers_2_pci_2_first
   *   %u_boot_list_2_drivers_2_pci_2_second
   *   %u_boot_list_2_drivers_2_pci_2_third
   *   %u_boot_list_2_drivers_2_pci_3
   *   %u_boot_list_2_drivers_3
   */

  /**
   * 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.

   *
   * 4) 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, 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)))
  
  /**
   * 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
  ", 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 LG-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_entry_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__ */