Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
net: apple: bmac: use crc32() instead of hand-rolled equivalent
The calculation done by bmac_crc(addr) followed by taking the low 6 bits
and reversing them is equivalent to taking the high 6 bits from
crc32(~0, addr, ETH_ALEN). Just do that instead.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://patch.msgid.link/20250513050142.635391-1-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
authored by
Eric Biggers
and committed by
Jakub Kicinski
a1dc1dee
88906f55
+2
-58
+2
-58
drivers/net/ethernet/apple/bmac.c
+2
-58
drivers/net/ethernet/apple/bmac.c
···
20
20
#include <linux/init.h>
21
21
#include <linux/spinlock.h>
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22
#include <linux/crc32.h>
23
-
#include <linux/crc32poly.h>
24
23
#include <linux/bitrev.h>
25
24
#include <linux/ethtool.h>
26
25
#include <linux/slab.h>
···
795
796
}
796
797
797
798
#ifndef SUNHME_MULTICAST
798
-
/* Real fast bit-reversal algorithm, 6-bit values */
799
-
static int reverse6[64] = {
800
-
0x0,0x20,0x10,0x30,0x8,0x28,0x18,0x38,
801
-
0x4,0x24,0x14,0x34,0xc,0x2c,0x1c,0x3c,
802
-
0x2,0x22,0x12,0x32,0xa,0x2a,0x1a,0x3a,
803
-
0x6,0x26,0x16,0x36,0xe,0x2e,0x1e,0x3e,
804
-
0x1,0x21,0x11,0x31,0x9,0x29,0x19,0x39,
805
-
0x5,0x25,0x15,0x35,0xd,0x2d,0x1d,0x3d,
806
-
0x3,0x23,0x13,0x33,0xb,0x2b,0x1b,0x3b,
807
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0x7,0x27,0x17,0x37,0xf,0x2f,0x1f,0x3f
808
-
};
809
-
810
-
static unsigned int
811
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crc416(unsigned int curval, unsigned short nxtval)
812
-
{
813
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unsigned int counter, cur = curval, next = nxtval;
814
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int high_crc_set, low_data_set;
815
-
816
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/* Swap bytes */
817
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next = ((next & 0x00FF) << 8) | (next >> 8);
818
-
819
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/* Compute bit-by-bit */
820
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for (counter = 0; counter < 16; ++counter) {
821
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/* is high CRC bit set? */
822
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if ((cur & 0x80000000) == 0) high_crc_set = 0;
823
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else high_crc_set = 1;
824
-
825
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cur = cur << 1;
826
-
827
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if ((next & 0x0001) == 0) low_data_set = 0;
828
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else low_data_set = 1;
829
-
830
-
next = next >> 1;
831
-
832
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/* do the XOR */
833
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if (high_crc_set ^ low_data_set) cur = cur ^ CRC32_POLY_BE;
834
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}
835
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return cur;
836
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}
837
-
838
-
static unsigned int
839
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bmac_crc(unsigned short *address)
840
-
{
841
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unsigned int newcrc;
842
-
843
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XXDEBUG(("bmac_crc: addr=%#04x, %#04x, %#04x\n", *address, address[1], address[2]));
844
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newcrc = crc416(0xffffffff, *address); /* address bits 47 - 32 */
845
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newcrc = crc416(newcrc, address[1]); /* address bits 31 - 16 */
846
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newcrc = crc416(newcrc, address[2]); /* address bits 15 - 0 */
847
-
848
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return(newcrc);
849
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}
850
-
851
799
/*
852
800
* Add requested mcast addr to BMac's hash table filter.
853
801
*
···
807
861
unsigned short mask;
808
862
809
863
if (!(*addr)) return;
810
-
crc = bmac_crc((unsigned short *)addr) & 0x3f; /* Big-endian alert! */
811
-
crc = reverse6[crc]; /* Hyperfast bit-reversing algorithm */
864
+
crc = crc32(~0, addr, ETH_ALEN) >> 26;
812
865
if (bp->hash_use_count[crc]++) return; /* This bit is already set */
813
866
mask = crc % 16;
814
867
mask = (unsigned char)1 << mask;
···
821
876
unsigned char mask;
822
877
823
878
/* Now, delete the address from the filter copy, as indicated */
824
-
crc = bmac_crc((unsigned short *)addr) & 0x3f; /* Big-endian alert! */
825
-
crc = reverse6[crc]; /* Hyperfast bit-reversing algorithm */
879
+
crc = crc32(~0, addr, ETH_ALEN) >> 26;
826
880
if (bp->hash_use_count[crc] == 0) return; /* That bit wasn't in use! */
827
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if (--bp->hash_use_count[crc]) return; /* That bit is still in use */
828
882
mask = crc % 16;