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_DMAphys_addr_t		dma_zone_size;	/* size of DMA-able area */
#endifunsigned 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;	/* default restart mode	*/unsigned		l2c_aux_val;	/* L2 cache aux value	*/unsigned		l2c_aux_mask;	/* L2 cache aux mask	*/void			(*l2c_write_sec)(unsigned long, unsigned);const struct smp_operations	*smp;	/* SMP operations	*/bool			(*smp_init