LINUX中使用DT_MACHINE_START/MACHINE_START宏

LINUX中使用DT_MACHINE_START/MACHINE_START宏

DT_MACHINE_START宏

LINUX中用DT_MACHINE_START/MACHINE_START定义的MACH，并给出定义的各个成员函数在初始化过程中被调用的时机

比如，kernel/arch/arm/mach-vexpress/v2m.c:

// SPDX-License-Identifier: GPL-2.0
#include <asm/mach/arch.h>

#include "core.h"

static const char * const v2m_dt_match[] __initconst = {
   
	"arm,vexpress",
	NULL,
};

DT_MACHINE_START(VEXPRESS_DT, "ARM-Versatile Express")
	.dt_compat	= v2m_dt_match,
	.l2c_aux_val	= 0x00400000,
	.l2c_aux_mask	= 0xfe0fffff,
	.smp		= smp_ops(vexpress_smp_dt_ops),
	.smp_init	= smp_init_ops(vexpress_smp_init_ops),
MACHINE_END

DT_MACHINE_START定义：

/*
设置多个宏来定义其体系结构和功能。这些宏由链接器将其构建为一个可执行的表。
*/
#define MACHINE_START(_type,_name)			\
static const struct machine_desc __mach_desc_##_type	\
 __used							\
 __attribute__((__section__(".arch.info.init"))) = {
     	\
	.nr		= MACH_TYPE_##_type,		\
	.name		= _name,

#define MACHINE_END				\
};

#define DT_MACHINE_START(_name, _namestr)		\
static const struct machine_desc __mach_desc_##_name	\
 __used							\
 __attribute__((__section__(".arch.info.init"))) = {
     	\
	.nr		= ~0,				\
	.name		= _namestr,

#endif

展开为：

static const struct machine_desc   __mach_desc_VEXPRESS_DT{
 __used                            
 __attribute__((__section__(".arch.info.init"))) = {
  	.name = "ARM-Versatile Express",
        ...
        ....
        ......
 };

定义了struct machine_desc类型的变量__mach_desc_VEXPRESS_DT，将其放在section(“.arch.info.init”)，是内核初始化数据。

看一下这个机器描述符结构：

struct machine_desc {
   
	unsigned int		nr;		/* architecture number	*/
	const char		*name;		/* architecture name	*/
	unsigned long		atag_offset;	/* tagged list (relative) */
	const char *const 	*dt_compat;	/* array of device tree
						 * 'compatible' strings	*/

	unsigned int		nr_irqs;	/* number of IRQs */

#ifdef CONFIG_ZONE_DMA
	phys_addr_t		dma_zone_size;	/* size of DMA-able area */
#endif

	unsigned int		video_start;	/* start of video RAM	*/
	unsigned int		video_end;	/* end of video RAM	*/

	unsigned char		reserve_lp0 :1;	/* never has lp0	*/
	unsigned char		reserve_lp1 :1;	/* never has lp1	*/
	unsigned char		reserve_lp2 :1;	/* never has lp2	*/
	enum reboot_mode	reboot_mode;