Commit a1dc1dee authored by Eric Biggers's avatar Eric Biggers Committed by Jakub Kicinski
Browse files

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: default avatarEric Biggers <ebiggers@google.com>
Link: https://patch.msgid.link/20250513050142.635391-1-ebiggers@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 88906f55

drivers/net/ethernet/apple/bmac.c

+2 −58
Original line number Diff line number Diff line
@@ -20,7 +20,6 @@ 
#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>
@@ -796,59 +795,6 @@ static irqreturn_t bmac_txdma_intr(int irq, void *dev_id) 
}



#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.

 *
@@ -861,8 +807,7 @@ bmac_addhash(struct bmac_data *bp, unsigned char *addr) 
	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;
@@ -876,8 +821,7 @@ bmac_removehash(struct bmac_data *bp, unsigned char *addr) 
	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;