Symbol: THINKPAD_EVENT_VOLUME_UP
sys/dev/acpica/acpi_thinkpad/acpi_thinkpad.c
1469
case THINKPAD_EVENT_VOLUME_UP:
sys/dev/acpica/acpi_thinkpad/acpi_thinkpad.c
1477
val = (arg == THINKPAD_EVENT_VOLUME_UP) ? val + 1 : val - 1;