taglinefilesource code
KG_ALT29drivers/char/kbd_kern.h#define VC_ALTLOCK  KG_ALT    /* alt lock mode */
KG_ALT363include/linux/keyboard.h#define K_ALT    K(KT_SHIFT,KG_ALT)
KG_ALT402include/linux/keyboard.h#define K_ALTLOCK  K(KT_LOCK,KG_ALT)