lib/raid6: Add log-of-2 table for RAID6 HW requiring disk position
The raid6_gfexp table represents {2}^n values for 0 <= n < 256. The
Linux async_tx framework pass values from raid6_gfexp as coefficients
for each source to prep_dma_pq() callback of DMA channel with PQ
capability. This creates problem for RAID6 offload engines (such as
Broadcom SBA) which take disk position (i.e. log of {2}) instead of
multiplicative cofficients from raid6_gfexp table.
This patch adds raid6_gflog table having log-of-2 value for any given
x such that 0 <= x < 256. For any given disk coefficient x, the
corresponding disk position is given by raid6_gflog[x]. The RAID6
offload engine driver can use this newly added raid6_gflog table to
get disk position from multiplicative coefficient.
Signed-off-by: Anup Patel <anup.patel@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Acked-by: Shaohua Li <shli@fb.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/lib/raid6/mktables.c b/lib/raid6/mktables.c
index 39787db..e824d08 100644
--- a/lib/raid6/mktables.c
+++ b/lib/raid6/mktables.c
@@ -125,6 +125,26 @@
printf("EXPORT_SYMBOL(raid6_gfexp);\n");
printf("#endif\n");
+ /* Compute log-of-2 table */
+ printf("\nconst u8 __attribute__((aligned(256)))\n"
+ "raid6_gflog[256] =\n" "{\n");
+ for (i = 0; i < 256; i += 8) {
+ printf("\t");
+ for (j = 0; j < 8; j++) {
+ v = 255;
+ for (k = 0; k < 256; k++)
+ if (exptbl[k] == (i + j)) {
+ v = k;
+ break;
+ }
+ printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
+ }
+ }
+ printf("};\n");
+ printf("#ifdef __KERNEL__\n");
+ printf("EXPORT_SYMBOL(raid6_gflog);\n");
+ printf("#endif\n");
+
/* Compute inverse table x^-1 == x^254 */
printf("\nconst u8 __attribute__((aligned(256)))\n"
"raid6_gfinv[256] =\n" "{\n");