mtd: mtd_nandecctest: support injecting bit error for ecc code

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=c092b43906098a6879d0fa9f74e5141516b9b856
Commit:     c092b43906098a6879d0fa9f74e5141516b9b856
Parent:     3cf06f4f85aea715e8caf8540760faff2fbf86d6
Author:     Akinobu Mita <akinobu.mita at gmail.com>
AuthorDate: Sat Sep 8 01:48:06 2012 +0900
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Sat Sep 29 15:47:28 2012 +0100

    mtd: mtd_nandecctest: support injecting bit error for ecc code
    
    Currently inject_single_bit_error() is used to inject single bit error
    into randomly selected bit position of the 256 or 512 bytes data block.
    
    Later change will add tests which inject bit errors into the ecc code.
    Unfortunately, inject_single_bit_error() doesn't work for the ecc code
    which is not a multiple of sizeof(unsigned long).
    
    Because bit fliping at random position is done by __change_bit().
    For example, flipping bit position 0 by __change_bit(0, addr) modifies
    3rd byte (32bit) or 7th byte (64bit) on big-endian systems.
    
    Using little-endian version of bitops can fix this issue.  But
    little-endian version of __change_bit is not yet available.
    So this defines __change_bit_le() locally in a similar fashion to
    asm-generic/bitops/le.h and use it.
    
    Signed-off-by: Akinobu Mita <akinobu.mita at gmail.com>
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/tests/mtd_nandecctest.c |   18 ++++++++++++++++--
 1 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/tests/mtd_nandecctest.c b/drivers/mtd/tests/mtd_nandecctest.c
index d3e8873..d90daf8 100644
--- a/drivers/mtd/tests/mtd_nandecctest.c
+++ b/drivers/mtd/tests/mtd_nandecctest.c
@@ -9,11 +9,25 @@
 
 #if defined(CONFIG_MTD_NAND) || defined(CONFIG_MTD_NAND_MODULE)
 
+/*
+ * The reason for this __change_bit_le() instead of __change_bit() is to inject
+ * bit error properly within the region which is not a multiple of
+ * sizeof(unsigned long) on big-endian systems
+ */
+#ifdef __LITTLE_ENDIAN
+#define __change_bit_le(nr, addr) __change_bit(nr, addr)
+#elif defined(__BIG_ENDIAN)
+#define __change_bit_le(nr, addr) \
+		__change_bit((nr) ^ ((BITS_PER_LONG - 1) & ~0x7), addr)
+#else
+#error "Unknown byte order"
+#endif
+
 static void inject_single_bit_error(void *data, size_t size)
 {
-	unsigned long offset = random32() % (size * BITS_PER_BYTE);
+	unsigned int offset = random32() % (size * BITS_PER_BYTE);
 
-	__change_bit(offset, data);
+	__change_bit_le(offset, data);
 }
 
 static void dump_data_ecc(void *error_data, void *error_ecc, void *correct_data,