Device Tree (四) - device_node -＞ platform_device

一，调用到of_platform_populate的流程

kernel V5.10:
start_kernel(void)
----setup_arch(&command_line);
--------setup_machine_fdt(__fdt_pointer); /* D:\work\source_code\msm-kernel\msm_kernel\arch\arm64\kernel\setup.c */
--------unflatten_device_tree(); /* D:\work\source_code\msm-kernel\msm_kernel\drivers\of\fdt.c */
----arch_call_rest_init();
--------rest_init();
------------kernel_thread(kernel_init, NULL, CLONE_FS);
----------------kernel_init_freeable();
--------------------do_basic_setup();
------------------------driver_init();
----------------------------firmware_init(); /* D:\work\source_code\msm-kernel\msm_kernel\drivers\base\firmware.c */
--------------------------------firmware_kobj = kobject_create_and_add("firmware", NULL);
----------------------------of_core_init();
--------------------------------of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
--------------------------------__of_attach_node_sysfs(np);
--------------------------------proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
----------------------------platform_bus_init();
------------------------do_initcalls();
--------------------------------do_initcall_level(level, command_line);
--------------------------------arch_initcall_sync(of_platform_default_populate_init);
------------------------------------of_platform_populate(root, of_default_bus_match_table, lookup, parent); /* D:\work\source_code\msm-kernel\msm_kernel\drivers\of\platform.c */

二，Device_Tree与sysfs

在of_core_init()函数中在/sys/firmware/devicetree/base目录下面为设备树展开成sysfs的目录和二进制属性文件，所有的node节点就是一个目录，所有的property属性就是一个二进制属性文件。

1， 创建/sys/firmware 目录

int __init firmware_init(void)
{
    firmware_kobj = kobject_create_and_add("firmware", NULL);
    if (!firmware_kobj)
        return -ENOMEM;
    return 0;
}

2， of_core_init

void __init of_core_init(void)
{
    struct device_node *np;

    /* Create the kset, and register existing nodes */
    mutex_lock(&of_mutex);
    //创建/sys/firmware/devicetree目录
    of_kset = kset_create_and_add("devicetree", NULL, firmware_kobj);
    if (!of_kset) {
        mutex_unlock(&of_mutex);
        pr_err("failed to register existing nodes\n");
        return;
    }

    for_each_of_allnodes(np) {
        //为设备树展开成sysfs的目录和二进制属性文件
        __of_attach_node_sysfs(np);
        if (np->phandle && !phandle_cache[of_phandle_cache_hash(np->phandle)])
            phandle_cache[of_phandle_cache_hash(np->phandle)] = np;
    }
    mutex_unlock(&of_mutex);

    /* Symlink in /proc as required by userspace ABI */
    if (of_root)
        //创建软链接 /proc/device-tree -> /sys/firmware/devicetree/base
        proc_symlink("device-tree", NULL, "/sys/firmware/devicetree/base");
}

3， __of_attach_node_sysfs

int __of_attach_node_sysfs(struct device_node *np)
{
    const char *name;
    struct kobject *parent;
    struct property *pp;
    int rc;

    if (!IS_ENABLED(CONFIG_SYSFS) || !of_kset)
        return 0;

    // kobj.kset
    np->kobj.kset = of_kset;
    if (!np->parent) {
        /* No