[Yaffs-archive] RE: Block Status Question

[Brad Beveridge]

I think it is because ECC can correct a 1 bit error.  The =
yaffs_isBlockBad function doesn't bother to do ECC so it is possible =
that there is a 1 bit error in the block status byte.  Counting the bits =
< 7 implies that 2 bits are bad & there is no chance that ECC will fix =
it.

Side note - if what I say is correct, perhaps the tags should be ECC =
fixed (if bits < 8) & then checked against 0xFF, otherwise it would be =
possible for the block status byte to have a single bit error, but also =
other bytes of the tag to have errors - which would also invalidate the =
ECC check?

Ie,=20
	if (countBits < 7)
		return 1;
	else
	if (countBits !=3D 0xFF)
	{
	  ecc_correct_tags
 	  if (corrected_status !=3D 0xFF)
	}

Cheers
Brad

> -----Original Message-----
> From: Jim Muchow [mailto:james.muchow@qlogic.com]=20
> Sent: Wednesday, 11 June 2003 4:20 a.m.
> To: yaffs@toby-churchill.org
> Subject: Block Status Question
>=20
>=20
> In yaffs_IsBlockBad() a test is made for the number of bits
> in each byte. The original test for 0xFF is #if'd out.
>=20
> The test for failure is less than 7. Shouldn't this be 8?
> What am I missing?
>=20
> JM
>=20
>=20
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