Linux 设备树展开 unflatten_device_tree 和 设备创建

asmlinkage __visible void __init __no_sanitize_address start_kernel(void) // init/main.c
	void __init __no_sanitize_address setup_arch(char **cmdline_p) //arch/arm64/kernel/setup.c
		if (acpi_disabled)
			unflatten_device_tree(); //drivers/of/fdt.c
				__unflatten_device_tree(initial_boot_params, NULL, &of_root,
				early_init_dt_alloc_memory_arch, false);
					size = unflatten_dt_nodes(blob, NULL, dad, NULL);·
					ret = unflatten_dt_nodes(blob, mem, dad, mynodes);
						ret = populate_node(blob, offset, &mem, nps[depth],&nps[depth+1], dryrun);
								populate_properties(blob, offset, mem, np, pathp, dryrun);
				/* Get pointer to "/chosen" and "/aliases" nodes for use everywhere */
				of_alias_scan(early_init_dt_alloc_memory_arch);

				unittest_unflatten_overlay_base();
		

root@Linux:~ >ls -al /proc/device-tree
lrwxrwxrwx 1 root root 29 Mar  1 07:54 /proc/device-tree -> /sys/firmware/devicetree/base
root@Linux:~ >

dtc -I fs -O dts /sys/firmware/devicetree/base/  -o linux_board.dts

start_kernel()
	arch_call_rest_init();
		rest_init();
			pid = user_mode_thread(kernel_init, NULL, CLONE_FS);
				kernel_init_freeable();
					do_basic_setup();
							cpuset_init_smp();
							driver_init();
									/* These are the core pieces */
									bdi_init(&noop_backing_dev_info);
									devtmpfs_init();
									devices_init();
									buses_init();
									classes_init();
									firmware_init();
									hypervisor_init();

									/* These are also core pieces, but must come after the
									 * core core pieces.
									 */
									of_core_init();
										proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
									platform_bus_init();
									auxiliary_bus_init();
									cpu_dev_init();
									memory_dev_init();
									node_dev_init();
									container_dev_init();
							init_irq_proc();
							do_ctors();
							do_initcalls();

static void __init do_initcalls(void)
{
	int level;
	size_t len = strlen(saved_command_line) + 1;
	char *command_line;

	command_line = kzalloc(len, GFP_KERNEL);
	if (!command_line)
		panic("%s: Failed to allocate %zu bytes\n", __func__, len);

	for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++) {
		/* Parser modifies command_line, restore it each time */
		strcpy(command_line, saved_command_line);
		do_initcall_level(level, command_line);
	}

	kfree(command_line);
}

static void __init do_initcall_level(int level, char *command_line)
{
	initcall_entry_t *fn;

	parse_args(initcall_level_names[level],
		   command_line, __start___param,
		   __stop___param - __start___param,
		   level, level,
		   NULL, ignore_unknown_bootoption);

	trace_initcall_level(initcall_level_names[level]);
	for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++)
		do_one_initcall(initcall_from_entry(fn));
}

int __init_or_module do_one_initcall(initcall_t fn)
{
	int count = preempt_count();
	char msgbuf[64];
	int ret;

	if (initcall_blacklisted(fn))
		return -EPERM;

	do_trace_initcall_start(fn);
	ret = fn();
	do_trace_initcall_finish(fn, ret);

	msgbuf[0] = 0;

	if (preempt_count() != count) {
		sprintf(msgbuf, "preemption imbalance ");
		preempt_count_set(count);
	}
	if (irqs_disabled()) {
		strlcat(msgbuf, "disabled interrupts ", sizeof(msgbuf));
		local_irq_enable();
	}
	WARN(msgbuf[0], "initcall %pS returned with %s\n", fn, msgbuf);

	add_latent_entropy();
	return ret;
}