[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: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --git a/include/linux/rslib.h b/include/linux/rslib.h
index ace25ac..746580c 100644 (file)
--- a/include/linux/rslib.h
+++ b/include/linux/rslib.h
@@ -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);

diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomon.c
index a4b730a..5b0d852 100644 (file)
--- a/lib/reed_solomon/reed_solomon.c
+++ b/lib/reed_solomon/reed_solomon.c
@@ -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);
@@ -99,17 +101,26 @@ 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 */
-       sr = 1;
-       for (i = 0; i < rs->nn; i++) {
-               rs->index_of[sr] = i;
-               rs->alpha_to[i] = sr;
-               sr <<= 1;
-               if (sr & (1 << symsize))
-                       sr ^= gfpoly;
-               sr &= rs->nn;
+       if (gfpoly) {
+               sr = 1;
+               for (i = 0; i < rs->nn; i++) {
+                       rs->index_of[sr] = i;
+                       rs->alpha_to[i] = sr;
+                       sr <<= 1;
+                       if (sr & (1 << symsize))
+                               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");