WM831X_AUX_BKUP_BATT
[WM831X_AUX_BKUP_BATT] = "Backup battery",
WM831X_NAMED_VOLTAGE(8, WM831X_AUX_BKUP_BATT);
ret = wm831x_backup_read_voltage(wm831x, WM831X_AUX_BKUP_BATT,