Driver initialization sequence __linux in Linux kernel startup

The Linux kernel defines different priority levels for different driver load sequences, as shown in the following macro:

Include/linux/init.h

#define Pure_initcall (FN) __define_initcall ("0", fn,1)
#define Core_initcall (FN) __define_initcall ("1", fn,1)
#define CORE_INITCALL_SYNC (FN) __define_initcall ("1s", fn,1s)
#define Postcore_initcall (FN) __define_initcall ("2", fn,2)
#define POSTCORE_INITCALL_SYNC (FN) __define_initcall ("2s", fn,2s)
#define Arch_initcall (FN) __define_initcall ("3", fn,3)
#define ARCH_INITCALL_SYNC (FN) __define_initcall ("3s", fn,3s)
#define Subsys_initcall (FN) __define_initcall ("4", fn,4)
#define SUBSYS_INITCALL_SYNC (FN) __define_initcall ("4s", fn,4s)
#define Fs_initcall (FN) __define_initcall ("5", fn,5)
#define FS_INITCALL_SYNC (FN) __define_initcall ("5s", fn,5s)
#define Rootfs_initcall (FN) __define_initcall ("Rootfs", Fn,rootfs)
#define Device_initcall (FN) __define_initcall ("6", fn,6)
#define DEVICE_INITCALL_SYNC (FN) __define_initcall ("6s", fn,6s)
#define Late_initcall (FN) __define_initcall ("7", fn,7)
#define LATE_INITCALL_SYNC (FN) __define_initcall ("7s", fn,7s)
#define __initcall (FN) Device_initcall (FN)

By using these macros to define your own driver's function name, you will have a different load-time priority. Wherein, the module_init used in our write drive corresponds to the #define MODULE_INIT (x) __initcall (x); #define __initcall (FN) Device_initcall (FN) Therefore, the driver corresponding to the load priority is 6.

In the different priorities above, the smaller the number, the higher the priority. The priority of the same level of driver, loading sequence is the link process decision, the result is uncertain, we can not go to manually set who first after. The order of driver loading at different levels is priority high and the lower priority is low, which can be determined. So, like we used before in the drive:
Module_init (I2c_dev_init);
Module_init (As352x_afe_init);
Module_init (As352x_afe_i2c_init);

So, everyone is initialized with the same priority, and finally these drivers are loaded in the order that you can view the generated System.map in the root directory:

。。。。。
C00197f4 T __initcall_default_rootfsrootfs
C00197f8 T __INITCALL_TIMER_INIT_SYSFS6
C00197FC T __initcall_clock_dev_init6
。。。