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Message-ID: <20250513050142.635391-1-ebiggers@kernel.org>
Date: Mon, 12 May 2025 22:01:42 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: netdev@...r.kernel.org
Subject: [PATCH net-next] net: apple: bmac: use crc32() instead of hand-rolled equivalent
From: Eric Biggers <ebiggers@...gle.com>
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@...gle.com>
---
drivers/net/ethernet/apple/bmac.c | 60 ++-----------------------------
1 file changed, 2 insertions(+), 58 deletions(-)
diff --git a/drivers/net/ethernet/apple/bmac.c b/drivers/net/ethernet/apple/bmac.c
index b9fdd61f1fdb..b50052c25a91 100644
--- a/drivers/net/ethernet/apple/bmac.c
+++ b/drivers/net/ethernet/apple/bmac.c
@@ -18,11 +18,10 @@
#include <linux/timer.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/crc32.h>
-#include <linux/crc32poly.h>
#include <linux/bitrev.h>
#include <linux/ethtool.h>
#include <linux/slab.h>
#include <linux/pgtable.h>
#include <asm/dbdma.h>
@@ -794,63 +793,10 @@ static irqreturn_t bmac_txdma_intr(int irq, void *dev_id)
bmac_start(dev);
return IRQ_HANDLED;
}
#ifndef SUNHME_MULTICAST
-/* Real fast bit-reversal algorithm, 6-bit values */
-static int reverse6[64] = {
- 0x0,0x20,0x10,0x30,0x8,0x28,0x18,0x38,
- 0x4,0x24,0x14,0x34,0xc,0x2c,0x1c,0x3c,
- 0x2,0x22,0x12,0x32,0xa,0x2a,0x1a,0x3a,
- 0x6,0x26,0x16,0x36,0xe,0x2e,0x1e,0x3e,
- 0x1,0x21,0x11,0x31,0x9,0x29,0x19,0x39,
- 0x5,0x25,0x15,0x35,0xd,0x2d,0x1d,0x3d,
- 0x3,0x23,0x13,0x33,0xb,0x2b,0x1b,0x3b,
- 0x7,0x27,0x17,0x37,0xf,0x2f,0x1f,0x3f
-};
-
-static unsigned int
-crc416(unsigned int curval, unsigned short nxtval)
-{
- unsigned int counter, cur = curval, next = nxtval;
- int high_crc_set, low_data_set;
-
- /* Swap bytes */
- next = ((next & 0x00FF) << 8) | (next >> 8);
-
- /* Compute bit-by-bit */
- for (counter = 0; counter < 16; ++counter) {
- /* is high CRC bit set? */
- if ((cur & 0x80000000) == 0) high_crc_set = 0;
- else high_crc_set = 1;
-
- cur = cur << 1;
-
- if ((next & 0x0001) == 0) low_data_set = 0;
- else low_data_set = 1;
-
- next = next >> 1;
-
- /* do the XOR */
- if (high_crc_set ^ low_data_set) cur = cur ^ CRC32_POLY_BE;
- }
- return cur;
-}
-
-static unsigned int
-bmac_crc(unsigned short *address)
-{
- unsigned int newcrc;
-
- XXDEBUG(("bmac_crc: addr=%#04x, %#04x, %#04x\n", *address, address[1], address[2]));
- newcrc = crc416(0xffffffff, *address); /* address bits 47 - 32 */
- newcrc = crc416(newcrc, address[1]); /* address bits 31 - 16 */
- newcrc = crc416(newcrc, address[2]); /* address bits 15 - 0 */
-
- return(newcrc);
-}
-
/*
* Add requested mcast addr to BMac's hash table filter.
*
*/
@@ -859,12 +805,11 @@ bmac_addhash(struct bmac_data *bp, unsigned char *addr)
{
unsigned int crc;
unsigned short mask;
if (!(*addr)) return;
- crc = bmac_crc((unsigned short *)addr) & 0x3f; /* Big-endian alert! */
- crc = reverse6[crc]; /* Hyperfast bit-reversing algorithm */
+ crc = crc32(~0, addr, ETH_ALEN) >> 26;
if (bp->hash_use_count[crc]++) return; /* This bit is already set */
mask = crc % 16;
mask = (unsigned char)1 << mask;
bp->hash_use_count[crc/16] |= mask;
}
@@ -874,12 +819,11 @@ bmac_removehash(struct bmac_data *bp, unsigned char *addr)
{
unsigned int crc;
unsigned char mask;
/* Now, delete the address from the filter copy, as indicated */
- crc = bmac_crc((unsigned short *)addr) & 0x3f; /* Big-endian alert! */
- crc = reverse6[crc]; /* Hyperfast bit-reversing algorithm */
+ crc = crc32(~0, addr, ETH_ALEN) >> 26;
if (bp->hash_use_count[crc] == 0) return; /* That bit wasn't in use! */
if (--bp->hash_use_count[crc]) return; /* That bit is still in use */
mask = crc % 16;
mask = ((unsigned char)1 << mask) ^ 0xffff; /* To turn off bit */
bp->hash_table_mask[crc/16] &= mask;
base-commit: e39d14a760c039af0653e3df967e7525413924a0
--
2.49.0
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