NAME
    TD_FORMAT/ETD_FORMAT -- format a track on a disk.

FUNCTION
    These commands are used to write data to a track that either
    has not yet been formatted or has had a hard error on a standard write
    command. TD_FORMAT completely ignores all data currently on a track and
    does not check for disk change before performing the command. The
    io_Data field must point to at least one track worth of data. The
    io_Offset field must be track aligned, and the io_Length field must be
    in units of track length (that is, NUMSEC*TD_SECTOR).

    The device will format the requested tracks, filling each sector with
    the contents of the buffer pointed to by io_Data. You
    should do a read pass to verify the data.

    If you have a hard write error during a normal write, you may find it
    possible to use the TD_FORMAT command to reformat the track as part of
    your error recovery process. ETD_FORMAT will write the sector label
    area if iotd_SecLabel is non-NULL.

IO REQUEST INPUT
    io_Device       preset by the call to opendevice()
    io_Unit         preset by the call to opendevice()
    io_Command      TD_FORMAT or ETD_FORMAT
    io_Flags        0 or IOF_QUICK
    io_Data         points to a buffer containing the data to write to the
                    track, must be at least as large as io_Length.
    io_Length       number of bytes to format, must be a multiple of
                    (TD_SECTORS * NUMSEC).
    io_Offset       byte offset from the start of the disk for the track to
                    format, must be a multiple of (TD_SECTORS * NUMSEC).
    iotd_Count      (ETD_FORMAT only) maximum allowable change counter
                    value.
    iotd_SecLabel   (ETD_FORMAT only) NULL or sector label buffer pointer.
                    If provided, the buffer must be a multiple of
                    (TD_LABELSIZE * NUMSEC).

IO REQUEST RESULT
    io_Error - 0 for success, or an error code as defined in
               <devices/trackdisk.h>

NOTES
    Under versions of Kickstart earlier than V36, the io_Data had to
    point to a buffer in chip memory. This restriction is no longer
    present as of Kickstart V36 and beyond.

SEE ALSO
    cmd_write, td_rawwrite