[Yaffs] Strange ECC Error

[Daniel Gustafsson]

Can somebody please explain the functions below. I am using yaffs/direct,
ECC turned off.

When scanning the emfile during a mount there are ecc errors.



void yaffs_CalcTagsECC(yaffs_Tags *tags)
{
	// Calculate an ecc
	
	unsigned char *b = ((yaffs_TagsUnion *)tags)->asBytes;
	unsigned  i,j;
	unsigned  ecc = 0;
	unsigned bit = 0;
	tags->ecc = 0;						

	for(i = 0; i < 8; i++)
	{
		for(j = 1; j &0xff; j<<=1)
		{
			bit++;
			if(b[i] & j)
			{
				ecc ^= bit;
			}
		}
	}
	
	tags->ecc = ecc;					%%%I always
get a high value on ecc approx 64
	
	
}

int  yaffs_CheckECCOnTags(yaffs_Tags *tags)
{
	unsigned ecc = tags->ecc;
	
	yaffs_CalcTagsECC(tags);
	
	ecc ^= tags->ecc;					%% Now my
ecc increases to approx 4096.
	
	if(ecc && ecc <= 64)
	{
		// TODO: Handle the failure better. Retire?
		unsigned char *b = ((yaffs_TagsUnion *)tags)->asBytes;

		ecc--;
				
		b[ecc / 8] ^= (1 << (ecc & 7));
		
		// Now recvalc the ecc
		yaffs_CalcTagsECC(tags);
		
		return 1; // recovered error
	}
	else if(ecc)
	{
		// Wierd ecc failure value
%%%% I always end up here.
		// TODO Need to do somethiong here
		return -1; //unrecovered error
	}
	
	return 0;
}



//Daniel