Hello,
I made several improvements to reed-solomon library.
Please have a look. :)
Thanks!
Changes in [PATCH v3]:
Fixed kernel-doc style. Thanks to Randy Dunlap :)
(But I decide to keep "a*b" instead of "a * b" because I think it's more
readable)
Reordered some patches to group similar things together.
Best Regards,
Zhang Boyang
===
Changes in [PATCH v2]:
Added more patches. Removed init_rs16(), since init_rs_non_canonical()
can do the same job.
Link: https://lore.kernel.org/all/[email protected]/
Changes in [PATCH v1]:
Added init_rs16().
Link: https://lore.kernel.org/all/[email protected]/
[RFC PATCH]:
Link: https://lore.kernel.org/all/[email protected]/
Currently the rslib allows customizing the finite field by the `gffunc'
parameter of init_rs_non_canonical(). However, there are several places
in rslib use hard-coded 1 instead of alpha_to[0], leading to errors if
gffunc(0) != 1. This patch fixes the problem. One of such `gffunc' might
be gffunc'(x) = swab16(gffunc(swab16(x))), as gffunc'(0) = swab16(1).
This special gffunc'(x) is useful when implementing RS coder for
16 bit foreign-endian symbols.
Signed-off-by: Zhang Boyang <[email protected]>
---
lib/reed_solomon/decode_rs.c | 4 ++--
lib/reed_solomon/reed_solomon.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c
index 805de84ae83d..6c1d53d1b702 100644
--- a/lib/reed_solomon/decode_rs.c
+++ b/lib/reed_solomon/decode_rs.c
@@ -104,7 +104,7 @@
decode:
memset(&lambda[1], 0, nroots * sizeof(lambda[0]));
- lambda[0] = 1;
+ lambda[0] = alpha_to[0];
if (no_eras > 0) {
/* Init lambda to be the erasure locator polynomial */
@@ -198,7 +198,7 @@
memcpy(®[1], &lambda[1], nroots * sizeof(reg[0]));
count = 0; /* Number of roots of lambda(x) */
for (i = 1, k = iprim - 1; i <= nn; i++, k = rs_modnn(rs, k + iprim)) {
- q = 1; /* lambda[0] is always 0 */
+ q = alpha_to[0]; /* lambda[0] is always 0 */
for (j = deg_lambda; j > 0; j--) {
if (reg[j] != nn) {
reg[j] = rs_modnn(rs, reg[j] + j);
diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomon.c
index bbc01bad3053..bb4f44c8edba 100644
--- a/lib/reed_solomon/reed_solomon.c
+++ b/lib/reed_solomon/reed_solomon.c
@@ -131,9 +131,9 @@ static struct rs_codec *codec_init(int symsize, int gfpoly, int (*gffunc)(int),
rs->iprim = iprim / prim;
/* Form RS code generator polynomial from its roots */
- rs->genpoly[0] = 1;
+ rs->genpoly[0] = rs->alpha_to[0];
for (i = 0, root = fcr * prim; i < nroots; i++, root += prim) {
- rs->genpoly[i + 1] = 1;
+ rs->genpoly[i + 1] = rs->alpha_to[0];
/* Multiply rs->genpoly[] by @**(root + x) */
for (j = i; j > 0; j--) {
if (rs->genpoly[j] != 0) {
--
2.30.2
This patch fixes the style of kernel-doc of rs_modnn().
Signed-off-by: Zhang Boyang <[email protected]>
---
include/linux/rslib.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/rslib.h b/include/linux/rslib.h
index cd0b5a7a5698..e92923fff3bc 100644
--- a/include/linux/rslib.h
+++ b/include/linux/rslib.h
@@ -107,7 +107,8 @@ struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
/* Release a rs control structure */
void free_rs(struct rs_control *rs);
-/** modulo replacement for galois field arithmetics
+/**
+ * rs_modnn() - Modulo replacement for galois field arithmetics
*
* @rs: Pointer to the RS codec
* @x: the value to reduce
--
2.30.2
This patch enhances the performance of RS encoder by following points:
1) Avoid memmove(). The shifting operation done by memmove() can be
merged into the calculation loop above.
2) Introduce rs_modnn_fast(). The original rs_modnn() contains a loop
which may be slow. Since (fb + genpoly[...]) is always strictly less
than (2 * rs->nn), we can use a ternary operator to do the same
calculation. The new faster function is named rs_modnn_fast(). The
new rs_modnn_fast(x) requires 0 <= x < 2*nn, in contrast, original
rs_modnn(x) only requires x >= 0. To make things clear, the
documentation of original rs_modnn() is also updated.
Signed-off-by: Zhang Boyang <[email protected]>
---
include/linux/rslib.h | 15 ++++++++++++++-
lib/reed_solomon/encode_rs.c | 21 ++++++++++-----------
2 files changed, 24 insertions(+), 12 deletions(-)
diff --git a/include/linux/rslib.h b/include/linux/rslib.h
index e92923fff3bc..a277a178157b 100644
--- a/include/linux/rslib.h
+++ b/include/linux/rslib.h
@@ -111,7 +111,7 @@ void free_rs(struct rs_control *rs);
* rs_modnn() - Modulo replacement for galois field arithmetics
*
* @rs: Pointer to the RS codec
- * @x: the value to reduce
+ * @x: x >= 0 ; the value to reduce
*
* where
* rs->mm = number of bits per symbol
@@ -128,4 +128,17 @@ static inline int rs_modnn(struct rs_codec *rs, int x)
return x;
}
+/**
+ * rs_modnn_fast() - Modulo replacement for galois field arithmetics
+ *
+ * @rs: Pointer to the RS codec
+ * @x: 0 <= x < 2*nn ; the value to reduce
+ *
+ * Same as rs_modnn(x), but faster, at the cost of limited value range of @x
+*/
+static inline int rs_modnn_fast(struct rs_codec *rs, int x)
+{
+ return x - rs->nn < 0 ? x : x - rs->nn;
+}
+
#endif
diff --git a/lib/reed_solomon/encode_rs.c b/lib/reed_solomon/encode_rs.c
index 9112d46e869e..6e3847b17ad4 100644
--- a/lib/reed_solomon/encode_rs.c
+++ b/lib/reed_solomon/encode_rs.c
@@ -27,19 +27,18 @@
for (i = 0; i < len; i++) {
fb = index_of[((((uint16_t) data[i])^invmsk) & msk) ^ par[0]];
- /* feedback term is non-zero */
if (fb != nn) {
- for (j = 1; j < nroots; j++) {
- par[j] ^= alpha_to[rs_modnn(rs, fb +
- genpoly[nroots - j])];
- }
- }
- /* Shift */
- memmove(&par[0], &par[1], sizeof(uint16_t) * (nroots - 1));
- if (fb != nn) {
- par[nroots - 1] = alpha_to[rs_modnn(rs,
- fb + genpoly[0])];
+ /* feedback term is non-zero */
+ for (j = 1; j < nroots; j++)
+ par[j - 1] = par[j] ^ alpha_to[rs_modnn_fast(rs,
+ fb +
+ genpoly[nroots - j])];
+ par[nroots - 1] = alpha_to[rs_modnn_fast(rs,
+ fb +
+ genpoly[0])];
} else {
+ for (j = 1; j < nroots; j++)
+ par[j - 1] = par[j];
par[nroots - 1] = 0;
}
}
--
2.30.2
Previous documentation of rs_modnn() states simple arithmetic modulo
return a wrong result for values >= (3 * rs->nn). However, that is not
true. The rs_modnn() does the exactly same job as (x % rs->nn). This can
be proved from following loop invariants:
while (x >= rs->nn) {
x -= rs->nn; // (1)
x = (x >> rs->mm) + (x & rs->nn); // (2)
}
Let x0 denote the value of x before assignment. At (1), it is obvious
that x % nn == x0 % nn. At (2), because nn == ((1 << mm) - 1), we have
x0 % nn == x0 % nn
x0 % nn == (((x0 >> mm) << mm) + (x0 & nn)) % nn
x0 % nn == ((x0 >> mm) * (nn + 1) + (x0 & nn)) % nn
x0 % nn == ((x0 >> mm) * ((nn + 1) % nn) + (x0 & nn)) % nn
x0 % nn == ((x0 >> mm) * 1 + (x0 & nn)) % nn // let's assume nn > 1
x0 % nn == ((x0 >> mm) + (x0 & nn)) % nn
x0 % nn == x % nn
When the loop exits, it is obvious that 0 <= x < nn, so the return value
must equal to (x % rs->nn).
Signed-off-by: Zhang Boyang <[email protected]>
---
include/linux/rslib.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/include/linux/rslib.h b/include/linux/rslib.h
index 238bb85243d3..507fa14c03b2 100644
--- a/include/linux/rslib.h
+++ b/include/linux/rslib.h
@@ -116,8 +116,7 @@ void free_rs(struct rs_control *rs);
* rs->mm = number of bits per symbol
* rs->nn = (2^rs->mm) - 1
*
- * Simple arithmetic modulo would return a wrong result for values
- * >= 3 * rs->nn
+ * Calculate (x % rs->nn), without using a div instruction
*/
static inline int rs_modnn(struct rs_codec *rs, int x)
{
--
2.30.2
Current rslib support symsize up to 16, so the max value of rs->nn can
be 0xFFFF. Since fcr <= nn, prim <= nn, multiplications on them can
overflow easily, e.g. fcr*root[j], fcr*prim.
This patch fixes these problems by introducing rs_modnn_mul(a, b). This
function is same as rs_modnn(a*b) but it will avoid overflow when
calculating a*b. It requires 0 <= a <= nn && 0 <= b <= nn, because it
use uint32_t to do the multiplication internally, so there will be no
overflow as long as 0 <= a <= nn <= 0xFFFF && 0 <= b <= nn <= 0xFFFF. In
fact, if we use `unsigned int' everywhere, there is no need to have
rs_modnn_mul(). But the `unsigned int' approach has poor scalability and
it may bring us to the mess of signed and unsigned integers.
With rs_modnn(), the intermediate result is now restricted to [0, nn).
This enables us to use rs_modnn_fast(a+b) to replace rs_modnn(a+b), as
long as 0 <= a+b < 2*nn. The most common case is one addend in [0, nn]
and the other addend in [0, nn). The examples of values in [0, nn] are
fcr, prim, indexes taken from rs->index_of[0...nn], etc. The examples of
values in [0, nn) are results from rs_modnn(), indexes taken from
rs->index_of[1...nn], etc.
Since the roots of RS generator polynomial, i.e. (fcr+i)*prim%nn, is
often used. It's now precomputed into rs->genroot[], to avoid writing
rs_modnn_mul(rs, rs_modnn_fast(rs, fcr + i), prim) everywhere.
The algorithm of searching for rs->iprim is also changed. Instead of
searching for (1+what*nn)%prim == 0, then iprim = (1+what*nn)/prim, it
now searches for iprim*prim%nn == 1 directly.
A new test case is also added to test_rslib.c to ensure correctness.
Signed-off-by: Zhang Boyang <[email protected]>
---
include/linux/rslib.h | 23 +++++++++++++
lib/reed_solomon/decode_rs.c | 60 +++++++++++++++++++--------------
lib/reed_solomon/reed_solomon.c | 30 ++++++++++++-----
lib/reed_solomon/test_rslib.c | 8 ++---
4 files changed, 83 insertions(+), 38 deletions(-)
diff --git a/include/linux/rslib.h b/include/linux/rslib.h
index a277a178157b..a11ea5e8eb14 100644
--- a/include/linux/rslib.h
+++ b/include/linux/rslib.h
@@ -22,6 +22,7 @@
* @alpha_to: exp() lookup table
* @index_of: log() lookup table
* @genpoly: Generator polynomial
+ * @genroot: Roots of generator polynomial, index form
* @nroots: Number of generator roots = number of parity symbols
* @fcr: First consecutive root, index form
* @prim: Primitive element, index form
@@ -37,6 +38,7 @@ struct rs_codec {
uint16_t *alpha_to;
uint16_t *index_of;
uint16_t *genpoly;
+ uint16_t *genroot;
int nroots;
int fcr;
int prim;
@@ -128,6 +130,27 @@ static inline int rs_modnn(struct rs_codec *rs, int x)
return x;
}
+/**
+ * rs_modnn_mul() - Modulo replacement for galois field arithmetics
+ *
+ * @rs: Pointer to the RS codec
+ * @a: 0 <= a <= nn ; a*b is the value to reduce
+ * @b: 0 <= b <= nn ; a*b is the value to reduce
+ *
+ * Same as rs_modnn(a*b), but avoid integer overflow when calculating a*b
+*/
+static inline int rs_modnn_mul(struct rs_codec *rs, int a, int b)
+{
+ /* nn <= 0xFFFF, so (a * b) will not overflow uint32_t */
+ uint32_t x = (uint32_t)a * (uint32_t)b;
+ uint32_t nn = (uint32_t)rs->nn;
+ while (x >= nn) {
+ x -= nn;
+ x = (x >> rs->mm) + (x & nn);
+ }
+ return (int)x;
+}
+
/**
* rs_modnn_fast() - Modulo replacement for galois field arithmetics
*
diff --git a/lib/reed_solomon/decode_rs.c b/lib/reed_solomon/decode_rs.c
index 6c1d53d1b702..3387465ab429 100644
--- a/lib/reed_solomon/decode_rs.c
+++ b/lib/reed_solomon/decode_rs.c
@@ -20,6 +20,7 @@
int iprim = rs->iprim;
uint16_t *alpha_to = rs->alpha_to;
uint16_t *index_of = rs->index_of;
+ uint16_t *genroot = rs->genroot;
uint16_t u, q, tmp, num1, num2, den, discr_r, syn_error;
int count = 0;
int num_corrected;
@@ -69,8 +70,8 @@
} else {
syn[i] = ((((uint16_t) data[j]) ^
invmsk) & msk) ^
- alpha_to[rs_modnn(rs, index_of[syn[i]] +
- (fcr + i) * prim)];
+ alpha_to[rs_modnn_fast(rs,
+ index_of[syn[i]] + genroot[i])];
}
}
}
@@ -81,8 +82,8 @@
syn[i] = ((uint16_t) par[j]) & msk;
} else {
syn[i] = (((uint16_t) par[j]) & msk) ^
- alpha_to[rs_modnn(rs, index_of[syn[i]] +
- (fcr+i)*prim)];
+ alpha_to[rs_modnn_fast(rs,
+ index_of[syn[i]] + genroot[i])];
}
}
}
@@ -108,15 +109,17 @@
if (no_eras > 0) {
/* Init lambda to be the erasure locator polynomial */
- lambda[1] = alpha_to[rs_modnn(rs,
- prim * (nn - 1 - (eras_pos[0] + pad)))];
+ lambda[1] = alpha_to[rs_modnn_mul(rs,
+ prim, (nn - 1 - (eras_pos[0] + pad)))];
for (i = 1; i < no_eras; i++) {
- u = rs_modnn(rs, prim * (nn - 1 - (eras_pos[i] + pad)));
+ u = rs_modnn_mul(rs,
+ prim, (nn - 1 - (eras_pos[i] + pad)));
for (j = i + 1; j > 0; j--) {
tmp = index_of[lambda[j - 1]];
if (tmp != nn) {
lambda[j] ^=
- alpha_to[rs_modnn(rs, u + tmp)];
+ alpha_to[rs_modnn_fast(rs,
+ u + tmp)];
}
}
}
@@ -137,9 +140,9 @@
for (i = 0; i < r; i++) {
if ((lambda[i] != 0) && (s[r - i - 1] != nn)) {
discr_r ^=
- alpha_to[rs_modnn(rs,
- index_of[lambda[i]] +
- s[r - i - 1])];
+ alpha_to[rs_modnn_fast(rs,
+ index_of[lambda[i]] +
+ s[r - i - 1])];
}
}
discr_r = index_of[discr_r]; /* Index form */
@@ -153,8 +156,8 @@
for (i = 0; i < nroots; i++) {
if (b[i] != nn) {
t[i + 1] = lambda[i + 1] ^
- alpha_to[rs_modnn(rs, discr_r +
- b[i])];
+ alpha_to[rs_modnn_fast(rs,
+ discr_r + b[i])];
} else
t[i + 1] = lambda[i + 1];
}
@@ -166,8 +169,9 @@
*/
for (i = 0; i <= nroots; i++) {
b[i] = (lambda[i] == 0) ? nn :
- rs_modnn(rs, index_of[lambda[i]]
- - discr_r + nn);
+ rs_modnn_fast(rs,
+ index_of[lambda[i]] +
+ nn - discr_r);
}
} else {
/* 2 lines below: B(x) <-- x*B(x) */
@@ -197,11 +201,11 @@
/* Find roots of error+erasure locator polynomial by Chien search */
memcpy(®[1], &lambda[1], nroots * sizeof(reg[0]));
count = 0; /* Number of roots of lambda(x) */
- for (i = 1, k = iprim - 1; i <= nn; i++, k = rs_modnn(rs, k + iprim)) {
+ for (i = 1, k = iprim-1; i <= nn; i++, k = rs_modnn_fast(rs, k+iprim)) {
q = alpha_to[0]; /* lambda[0] is always 0 */
for (j = deg_lambda; j > 0; j--) {
if (reg[j] != nn) {
- reg[j] = rs_modnn(rs, reg[j] + j);
+ reg[j] = rs_modnn_fast(rs, reg[j] + j);
q ^= alpha_to[reg[j]];
}
}
@@ -238,8 +242,8 @@
tmp = 0;
for (j = i; j >= 0; j--) {
if ((s[i - j] != nn) && (lambda[j] != nn))
- tmp ^=
- alpha_to[rs_modnn(rs, s[i - j] + lambda[j])];
+ tmp ^= alpha_to[rs_modnn_fast(rs,
+ s[i - j] + lambda[j])];
}
omega[i] = index_of[tmp];
}
@@ -254,8 +258,9 @@
num1 = 0;
for (i = deg_omega; i >= 0; i--) {
if (omega[i] != nn)
- num1 ^= alpha_to[rs_modnn(rs, omega[i] +
- i * root[j])];
+ num1 ^= alpha_to[rs_modnn_fast(rs,
+ omega[i] +
+ rs_modnn_mul(rs, i, root[j]))];
}
if (num1 == 0) {
@@ -264,15 +269,18 @@
continue;
}
- num2 = alpha_to[rs_modnn(rs, root[j] * (fcr - 1) + nn)];
+ num2 = alpha_to[rs_modnn_fast(rs,
+ rs_modnn_mul(rs, root[j], fcr) +
+ nn - root[j])];
den = 0;
/* lambda[i+1] for i even is the formal derivative
* lambda_pr of lambda[i] */
for (i = min(deg_lambda, nroots - 1) & ~1; i >= 0; i -= 2) {
if (lambda[i + 1] != nn) {
- den ^= alpha_to[rs_modnn(rs, lambda[i + 1] +
- i * root[j])];
+ den ^= alpha_to[rs_modnn_fast(rs,
+ lambda[i + 1] +
+ rs_modnn_mul(rs, i, root[j]))];
}
}
@@ -292,8 +300,8 @@
if (b[j] == 0)
continue;
- k = (fcr + i) * prim * (nn-loc[j]-1);
- tmp ^= alpha_to[rs_modnn(rs, index_of[b[j]] + k)];
+ k = rs_modnn_mul(rs, genroot[i], nn - loc[j] - 1);
+ tmp ^= alpha_to[rs_modnn_fast(rs, index_of[b[j]] + k)];
}
if (tmp != alpha_to[s[i]])
diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomon.c
index da46026a60b8..2c86e4dfcbaa 100644
--- a/lib/reed_solomon/reed_solomon.c
+++ b/lib/reed_solomon/reed_solomon.c
@@ -100,6 +100,10 @@ static struct rs_codec *codec_init(int symsize, int gfpoly, int (*gffunc)(int),
if(rs->genpoly == NULL)
goto err;
+ rs->genroot = kmalloc_array(rs->nroots, sizeof(uint16_t), gfp);
+ if(rs->genroot == NULL)
+ goto err;
+
/* Generate Galois field lookup tables */
rs->index_of[0] = rs->nn; /* log(zero) = -inf */
rs->alpha_to[rs->nn] = 0; /* alpha**-inf = 0 */
@@ -126,26 +130,34 @@ static struct rs_codec *codec_init(int symsize, int gfpoly, int (*gffunc)(int),
goto err;
/* Find prim-th root of 1, used in decoding */
- for(iprim = 1; (iprim % prim) != 0; iprim += rs->nn);
+ for (iprim = 1; rs_modnn_mul(rs, iprim, prim) != 1; iprim++);
/* prim-th root of 1, index form */
- rs->iprim = iprim / prim;
+ rs->iprim = iprim;
+
+ /* Precompute generator polynomial roots */
+ root = rs_modnn_mul(rs, fcr, prim);
+ for (i = 0; i < nroots; i++) {
+ rs->genroot[i] = root; /* = (fcr + i) * prim % nn */
+ root = rs_modnn_fast(rs, root + prim);
+ }
/* Form RS code generator polynomial from its roots */
rs->genpoly[0] = rs->alpha_to[0];
- for (i = 0, root = fcr * prim; i < nroots; i++, root += prim) {
+ for (i = 0; i < nroots; i++) {
+ root = rs->genroot[i];
rs->genpoly[i + 1] = rs->alpha_to[0];
/* Multiply rs->genpoly[] by @**(root + x) */
for (j = i; j > 0; j--) {
if (rs->genpoly[j] != 0) {
- rs->genpoly[j] = rs->genpoly[j -1] ^
- rs->alpha_to[rs_modnn(rs,
+ rs->genpoly[j] = rs->genpoly[j - 1] ^
+ rs->alpha_to[rs_modnn_fast(rs,
rs->index_of[rs->genpoly[j]] + root)];
} else
rs->genpoly[j] = rs->genpoly[j - 1];
}
/* rs->genpoly[0] can never be zero */
rs->genpoly[0] =
- rs->alpha_to[rs_modnn(rs,
+ rs->alpha_to[rs_modnn_fast(rs,
rs->index_of[rs->genpoly[0]] + root)];
}
/* convert rs->genpoly[] to index form for quicker encoding */
@@ -157,6 +169,7 @@ static struct rs_codec *codec_init(int symsize, int gfpoly, int (*gffunc)(int),
return rs;
err:
+ kfree(rs->genroot);
kfree(rs->genpoly);
kfree(rs->index_of);
kfree(rs->alpha_to);
@@ -188,6 +201,7 @@ void free_rs(struct rs_control *rs)
kfree(cd->alpha_to);
kfree(cd->index_of);
kfree(cd->genpoly);
+ kfree(cd->genroot);
kfree(cd);
}
mutex_unlock(&rslistlock);
@@ -340,7 +354,7 @@ EXPORT_SYMBOL_GPL(encode_rs8);
* @data: data field of a given type
* @par: received parity data field
* @len: data length
- * @s: syndrome data field, must be in index form
+ * @s: syndrome data field, must be in index form, 0 <= index <= nn
* (if NULL, syndrome is calculated)
* @no_eras: number of erasures
* @eras_pos: position of erasures, can be NULL
@@ -393,7 +407,7 @@ EXPORT_SYMBOL_GPL(encode_rs16);
* @data: data field of a given type
* @par: received parity data field
* @len: data length
- * @s: syndrome data field, must be in index form
+ * @s: syndrome data field, must be in index form, 0 <= index <= nn
* (if NULL, syndrome is calculated)
* @no_eras: number of erasures
* @eras_pos: position of erasures, can be NULL
diff --git a/lib/reed_solomon/test_rslib.c b/lib/reed_solomon/test_rslib.c
index d9d1c33aebda..a03c7249f920 100644
--- a/lib/reed_solomon/test_rslib.c
+++ b/lib/reed_solomon/test_rslib.c
@@ -55,6 +55,7 @@ static struct etab Tab[] = {
{8, 0x11d, 1, 1, 30, 100 },
{8, 0x187, 112, 11, 32, 100 },
{9, 0x211, 1, 1, 33, 80 },
+ {16, 0x1ffed, 65534, 65534, 50, 5 },
{0, 0, 0, 0, 0, 0},
};
@@ -232,9 +233,8 @@ static void compute_syndrome(struct rs_control *rsc, uint16_t *data,
struct rs_codec *rs = rsc->codec;
uint16_t *alpha_to = rs->alpha_to;
uint16_t *index_of = rs->index_of;
+ uint16_t *genroot = rs->genroot;
int nroots = rs->nroots;
- int prim = rs->prim;
- int fcr = rs->fcr;
int i, j;
/* Calculating syndrome */
@@ -245,8 +245,8 @@ static void compute_syndrome(struct rs_control *rsc, uint16_t *data,
syn[i] = data[j];
} else {
syn[i] = data[j] ^
- alpha_to[rs_modnn(rs, index_of[syn[i]]
- + (fcr + i) * prim)];
+ alpha_to[rs_modnn_fast(rs,
+ index_of[syn[i]] + genroot[i])];
}
}
}
--
2.30.2
This patch fixes some obvious documentation mistakes.
Signed-off-by: Zhang Boyang <[email protected]>
---
include/linux/rslib.h | 4 ++--
lib/reed_solomon/reed_solomon.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/rslib.h b/include/linux/rslib.h
index 507fa14c03b2..cd0b5a7a5698 100644
--- a/include/linux/rslib.h
+++ b/include/linux/rslib.h
@@ -19,8 +19,8 @@
*
* @mm: Bits per symbol
* @nn: Symbols per block (= (1<<mm)-1)
- * @alpha_to: log lookup table
- * @index_of: Antilog lookup table
+ * @alpha_to: exp() lookup table
+ * @index_of: log() lookup table
* @genpoly: Generator polynomial
* @nroots: Number of generator roots = number of parity symbols
* @fcr: First consecutive root, index form
diff --git a/lib/reed_solomon/reed_solomon.c b/lib/reed_solomon/reed_solomon.c
index bb4f44c8edba..da46026a60b8 100644
--- a/lib/reed_solomon/reed_solomon.c
+++ b/lib/reed_solomon/reed_solomon.c
@@ -56,7 +56,7 @@ static DEFINE_MUTEX(rslistlock);
/**
* codec_init - Initialize a Reed-Solomon codec
- * @symsize: symbol size, bits (1-8)
+ * @symsize: the symbol size (number of bits)
* @gfpoly: Field generator polynomial coefficients
* @gffunc: Field generator function
* @fcr: first root of RS code generator polynomial, index form
--
2.30.2
On 6/19/22 23:20, Zhang Boyang wrote:
> This patch fixes the style of kernel-doc of rs_modnn().
>
> Signed-off-by: Zhang Boyang <[email protected]>
Reviewed-by: Randy Dunlap <[email protected]>
Thanks.
> ---
> include/linux/rslib.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/rslib.h b/include/linux/rslib.h
> index cd0b5a7a5698..e92923fff3bc 100644
> --- a/include/linux/rslib.h
> +++ b/include/linux/rslib.h
> @@ -107,7 +107,8 @@ struct rs_control *init_rs_non_canonical(int symsize, int (*func)(int),
> /* Release a rs control structure */
> void free_rs(struct rs_control *rs);
>
> -/** modulo replacement for galois field arithmetics
> +/**
> + * rs_modnn() - Modulo replacement for galois field arithmetics
> *
> * @rs: Pointer to the RS codec
> * @x: the value to reduce
--
~Randy