I am trying to learn the serial mouse driver for linux kernel. On the kernel source tree I find out these macros and I am unable to find out the meaning of these macros. Please anyone help me to understand these.
These macros are defined in linux/serio.h and are used in the sermouse.c (driver code for serial mouse in linux).

#define SERIO_MSC 0x01
#define SERIO_SUN 0x02
#define SERIO_MS 0x03
#define SERIO_MP 0x04
#define SERIO_MZ 0x05
#define SERIO_MZP 0x06
#define SERIO_MZPP 0x07

I used Mr google but yielded no result. I think these macros indicate some certain protocols but I dont know what protocols. Can anyone help me to understand these.