[PATCH] pcmcia: fix modalias attribute in sysfs

[deliverable/linux.git] / Documentation / pcmcia / devicetable.txt

Matching of PCMCIA devices to drivers is done using one or more of the
following criteria:

- manufactor ID
- card ID
- product ID strings _and_ hashes of these strings
- function ID
- device function (actual and pseudo)

You should use the helpers in include/pcmcia/device_id.h for generating the
struct pcmcia_device_id[] entries which match devices to drivers.

If you want to match product ID strings, you also need to pass the crc32
hashes of the string to the macro, e.g. if you want to match the product ID
string 1, you need to use

PCMCIA_DEVICE_PROD_ID1("some_string", 0x(hash_of_some_string)),

If the hash is incorrect, the kernel will inform you about this in "dmesg"
upon module initialization, and tell you of the correct hash.

You can determine the hash of the product ID strings by running
"pcmcia-modalias %n.%m" [%n being replaced with the socket number and %m being
replaced with the device function] from pcmciautils. It generates a string
in the following form:
pcmcia:m0149cC1ABf06pfn00fn00pa725B842DpbF1EFEE84pc0877B627pd00000000

The hex value after "pa" is the hash of product ID string 1, after "pb" for
string 2 and so on.

Alternatively, you can use this small tool to determine the crc32 hash.
simply pass the string you want to evaluate as argument to this program,
e.g.
$ ./crc32hash "Dual Speed"

-------------------------------------------------------------------------
/* crc32hash.c - derived from linux/lib/crc32.c, GNU GPL v2 */
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

unsigned int crc32(unsigned char const *p, unsigned int len)
{
	int i;
	unsigned int crc = 0;
	while (len--) {
		crc ^= *p++;
		for (i = 0; i < 8; i++)
			crc = (crc >> 1) ^ ((crc & 1) ? 0xedb88320 : 0);
	}
	return crc;
}

int main(int argc, char **argv) {
	unsigned int result;
	if (argc != 2) {
		printf("no string passed as argument\n");
		return -1;
	}
	result = crc32(argv[1], strlen(argv[1]));
	printf("0x%x\n", result);
	return 0;
}