When you get no events notifications about power cable in-out on vaio, you must probably have hit the vaio bios bug. Practically it sends 0x81 event instead of 0x80. To fix it in current kernels distributed by your favorite vendor you have to add in ac.c :
#define ACPI_AC_NOTIFY_STATUS 0x80 +#define ACPI_AC_NOTIFY_SONY 0x81 #define ACPI_AC_STATUS_OFFLINE 0x00
and
case ACPI_AC_NOTIFY_STATUS: +case ACPI_AC_NOTIFY_SONY: case ACPI_NOTIFY_BUS_CHECK:
then recompile, overwrite the original in /lib/modules/….
modprobe -r ac && modprobe ac
all should be good now