Commit d7e5a546 authored by Segher Boessenkool's avatar Segher Boessenkool Committed by David Woodhouse
Browse files

[RSLIB] Support non-canonical GF representations 



For the CAFÉ NAND controller, we need to support non-canonical 
representations of the Galois field. Allow the caller to provide its own 
function for generating the field, and CAFÉ can use rslib instead of its
own implementation.

Signed-off-by: default avatarSegher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
parent 7c96b7a1

include/linux/rslib.h

+4 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
 * @prim:	Primitive element, index form

 * @iprim:	prim-th root of 1, index form

 * @gfpoly:	The primitive generator polynominal

 * @gffunc:	Function to generate the field, if non-canonical representation

 * @users:	Users of this structure

 * @list:	List entry for the rs control list

*/
@@ -48,6 +49,7 @@ struct rs_control { 
	int 		prim;

	int 		iprim;

	int		gfpoly;

	int		(*gffunc)(int);

	int		users;

	struct list_head list;

};
@@ -77,6 +79,8 @@ int decode_rs16(struct rs_control *rs, uint16_t *data, uint16_t *par, int len, 
/* Create or get a matching rs control structure */

struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,

			   int nroots);

struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),

                                         int fcr, int prim, int nroots);



/* Release a rs control structure */

void free_rs(struct rs_control *rs);

lib/reed_solomon/reed_solomon.c

+69 −15
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ static DEFINE_MUTEX(rslistlock); 
 * rs_init - Initialize a Reed-Solomon codec

 * @symsize:	symbol size, bits (1-8)

 * @gfpoly:	Field generator polynomial coefficients

 * @gffunc:	Field generator function

 * @fcr:	first root of RS code generator polynomial, index form

 * @prim:	primitive element to generate polynomial roots

 * @nroots:	RS code generator polynomial degree (number of roots)
@@ -63,8 +64,8 @@ static DEFINE_MUTEX(rslistlock); 
 * Allocate a control structure and the polynom arrays for faster

 * en/decoding. Fill the arrays according to the given parameters.

 */

static struct rs_control *rs_init(int symsize, int gfpoly, int fcr,

				   int prim, int nroots)

static struct rs_control *rs_init(int symsize, int gfpoly, int (*gffunc)(int),

                                  int fcr, int prim, int nroots)

{

	struct rs_control *rs;

	int i, j, sr, root, iprim;
@@ -82,6 +83,7 @@ static struct rs_control *rs_init(int symsize, int gfpoly, int fcr, 
	rs->prim = prim;

	rs->nroots = nroots;

	rs->gfpoly = gfpoly;

	rs->gffunc = gffunc;



	/* Allocate the arrays */

	rs->alpha_to = kmalloc(sizeof(uint16_t) * (rs->nn + 1), GFP_KERNEL);
@@ -99,6 +101,7 @@ static struct rs_control *rs_init(int symsize, int gfpoly, int fcr, 
	/* Generate Galois field lookup tables */

	rs->index_of[0] = rs->nn;	/* log(zero) = -inf */

	rs->alpha_to[rs->nn] = 0;	/* alpha**-inf = 0 */

	if (gfpoly) {

		sr = 1;

		for (i = 0; i < rs->nn; i++) {

			rs->index_of[sr] = i;
@@ -108,8 +111,16 @@ static struct rs_control *rs_init(int symsize, int gfpoly, int fcr, 
				sr ^= gfpoly;

			sr &= rs->nn;

		}

	} else {

		sr = gffunc(0);

		for (i = 0; i < rs->nn; i++) {

			rs->index_of[sr] = i;

			rs->alpha_to[i] = sr;

			sr = gffunc(sr);

		}

	}

	/* If it's not primitive, exit */

	if(sr != 1)

	if(sr != rs->alpha_to[0])

		goto errpol;



	/* Find prim-th root of 1, used in decoding */
@@ -173,18 +184,22 @@ void free_rs(struct rs_control *rs) 
}



/**

 * init_rs - Find a matching or allocate a new rs control structure

 * init_rs_internal - Find a matching or allocate a new rs control structure

 *  @symsize:	the symbol size (number of bits)

 *  @gfpoly:	the extended Galois field generator polynomial coefficients,

 *		with the 0th coefficient in the low order bit. The polynomial

 *		must be primitive;

 *  @gffunc:	pointer to function to generate the next field element,

 *		or the multiplicative identity element if given 0.  Used

 *		instead of gfpoly if gfpoly is 0

 *  @fcr:  	the first consecutive root of the rs code generator polynomial

 *		in index form

 *  @prim:	primitive element to generate polynomial roots

 *  @nroots:	RS code generator polynomial degree (number of roots)

 */

struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,

			   int nroots)

static struct rs_control *init_rs_internal(int symsize, int gfpoly,

                                           int (*gffunc)(int), int fcr,

                                           int prim, int nroots)

{

	struct list_head	*tmp;

	struct rs_control	*rs;
@@ -208,6 +223,8 @@ struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim, 
			continue;

		if (gfpoly != rs->gfpoly)

			continue;

		if (gffunc != rs->gffunc)

			continue;

		if (fcr != rs->fcr)

			continue;

		if (prim != rs->prim)
@@ -220,7 +237,7 @@ struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim, 
	}



	/* Create a new one */

	rs = rs_init(symsize, gfpoly, fcr, prim, nroots);

	rs = rs_init(symsize, gfpoly, gffunc, fcr, prim, nroots);

	if (rs) {

		rs->users = 1;

		list_add(&rs->list, &rslist);
@@ -230,6 +247,42 @@ out: 
	return rs;

}



/**

 * init_rs - Find a matching or allocate a new rs control structure

 *  @symsize:	the symbol size (number of bits)

 *  @gfpoly:	the extended Galois field generator polynomial coefficients,

 *		with the 0th coefficient in the low order bit. The polynomial

 *		must be primitive;

 *  @fcr:  	the first consecutive root of the rs code generator polynomial

 *		in index form

 *  @prim:	primitive element to generate polynomial roots

 *  @nroots:	RS code generator polynomial degree (number of roots)

 */

struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,

                           int nroots)

{

	return init_rs_internal(symsize, gfpoly, NULL, fcr, prim, nroots);

}



/**

 * init_rs_non_canonical - Find a matching or allocate a new rs control

 *                         structure, for fields with non-canonical

 *                         representation

 *  @symsize:	the symbol size (number of bits)

 *  @gffunc:	pointer to function to generate the next field element,

 *		or the multiplicative identity element if given 0.  Used

 *		instead of gfpoly if gfpoly is 0

 *  @fcr:  	the first consecutive root of the rs code generator polynomial

 *		in index form

 *  @prim:	primitive element to generate polynomial roots

 *  @nroots:	RS code generator polynomial degree (number of roots)

 */

struct rs_control *init_rs_non_canonical(int symsize, int (*gffunc)(int),

                                         int fcr, int prim, int nroots)

{

	return init_rs_internal(symsize, 0, gffunc, fcr, prim, nroots);

}



#ifdef CONFIG_REED_SOLOMON_ENC8

/**

 *  encode_rs8 - Calculate the parity for data values (8bit data width)
@@ -321,6 +374,7 @@ EXPORT_SYMBOL_GPL(decode_rs16); 
#endif



EXPORT_SYMBOL_GPL(init_rs);

EXPORT_SYMBOL_GPL(init_rs_non_canonical);

EXPORT_SYMBOL_GPL(free_rs);



MODULE_LICENSE("GPL");

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