NAND_CHECK_ERASED_EC(9)             Public Functions Provided             NAND_CHECK_ERASED_EC(9)



NAME
       nand_check_erased_ecc_chunk - check if an ECC chunk contains (almost) only 0xff data

SYNOPSIS
       int nand_check_erased_ecc_chunk(void * data, int datalen, void * ecc, int ecclen,
                                       void * extraoob, int extraooblen, int bitflips_threshold);

ARGUMENTS
       data
           data buffer to test

       datalen
           data length

       ecc
           ECC buffer

       ecclen
           ECC length

       extraoob
           extra OOB buffer

       extraooblen
           extra OOB length

       bitflips_threshold
           maximum number of bitflips

DESCRIPTION
       Check if a data buffer and its associated ECC and OOB data contains only 0xff pattern,
       which means the underlying region has been erased and is ready to be programmed. The
       bitflips_threshold specify the maximum number of bitflips before considering the region as
       not erased.

NOTE
       1/ ECC algorithms are working on pre-defined block sizes which are usually different from
       the NAND page size. When fixing bitflips, ECC engines will report the number of errors per
       chunk, and the NAND core infrastructure expect you to return the maximum number of
       bitflips for the whole page. This is why you should always use this function on a single
       chunk and not on the whole page. After checking each chunk you should update your
       max_bitflips value accordingly. 2/ When checking for bitflips in erased pages you should
       not only check the payload data but also their associated ECC data, because a user might
       have programmed almost all bits to 1 but a few. In this case, we shouldn't consider the
       chunk as erased, and checking ECC bytes prevent this case. 3/ The extraoob argument is
       optional, and should be used if some of your OOB data are protected by the ECC engine. It
       could also be used if you support subpages and want to attach some extra OOB data to an
       ECC chunk.

       Returns a positive number of bitflips less than or equal to bitflips_threshold, or
       -ERROR_CODE for bitflips in excess of the threshold. In case of success, the passed
       buffers are filled with 0xff.

AUTHOR
       Thomas Gleixner <tglx AT linutronix.de>
           Author.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                   NAND_CHECK_ERASED_EC(9)