FatFs - disk_status

## disk_status

The disk_status function is called to inquire the current drive status.

    DSTATUS disk_status (
      BYTE pdrv     /* [IN] Physical drive number */
    );

#### Parameter

pdrv
  Physical drive number to identify the target device. Always zero at single drive system.

#### Return Values

The current drive status is returned in combination of status flags described below. FatFs refers only `STA_NOINIT` and `STA_PROTECT`.

STA_NOINIT
  Indicates that the device is not initialized and not ready to work. This flag is set on system reset, media removal or failure of `disk_initialize` function. It is cleared on `disk_initialize` function succeeded. Any media change that occurs asynchronously must be captured and reflect it to the status flags, or auto-mount function will not work correctly. If the system does not support media change detection, application program needs to explicitly re-mount the volume with `f_mount` function after each media change.
STA_NODISK
  Indicates that no medium in the drive. This is always cleared at fixed disk drive. Note that FatFs does not refer this flag.
STA_PROTECT
  Indicates that the medium is write protected. This is always cleared at the drives without write protect function. Not valid if no medium in the drive.

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