[Yaffs] Strange ECC Error

[Charles Manning]

Are you getting the errors when scanning empty chunks/pages? If so, these=
 can=20
be safely ignored.=20

The "ECC turned off" does not apply to the tags ECC calculation, only to =
the=20
data ECC calculation.

-- Charles



On Wednesday 13 October 2004 03:48, Daniel Gustafsson wrote:
> Can somebody please explain the functions below. I am using yaffs/direc=
t,
> 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 =3D ((yaffs_TagsUnion *)tags)->asBytes;
> 	unsigned  i,j;
> 	unsigned  ecc =3D 0;
> 	unsigned bit =3D 0;
> 	tags->ecc =3D 0;
>
> 	for(i =3D 0; i < 8; i++)
> 	{
> 		for(j =3D 1; j &0xff; j<<=3D1)
> 		{
> 			bit++;
> 			if(b[i] & j)
> 			{
> 				ecc ^=3D bit;
> 			}
> 		}
> 	}
>
> 	tags->ecc =3D ecc;					%%%I always
> get a high value on ecc approx 64
>
>
> }
>
> int  yaffs_CheckECCOnTags(yaffs_Tags *tags)
> {
> 	unsigned ecc =3D tags->ecc;
>
> 	yaffs_CalcTagsECC(tags);
>
> 	ecc ^=3D tags->ecc;					%% Now my
> ecc increases to approx 4096.
>
> 	if(ecc && ecc <=3D 64)
> 	{
> 		// TODO: Handle the failure better. Retire?
> 		unsigned char *b =3D ((yaffs_TagsUnion *)tags)->asBytes;
>
> 		ecc--;
>
> 		b[ecc / 8] ^=3D (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
>
>
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