As with the MCU temperature and VREFINT measurement, this patch requires user to enable the corresponding channel first. For Vbat channel the ioctl cmd is IO_ENABLE_DISABLE_VBAT_CH, and its arg should be a pointer to bool which must be true to enable and false to disable the Vbat channel.
Moreover, since Vbat input contains a built-in voltage divider, it is highly suggested to disable Vbat input channel after measurement is done in order to prevent battery drain through the divider.
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