path: root/Documentation/pcmcia/devicetable.txt
diff options
authorDominik Brodowski <linux@dominikbrodowski.net>2005-06-27 16:28:45 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-27 18:03:18 -0700
commit5085cb26503a662a5cfdf53ce96fd606c1fbe9ba (patch)
tree93f4cc37b516e4f6a812b760e3a52d1b2d0dfd5b /Documentation/pcmcia/devicetable.txt
parentf4d7510d3d3b4501c94b4b00cf42fd58d49aeddd (diff)
[PATCH] pcmcia: add some Documentation
Add some information useful for PCMCIA device driver authors to Documentation/pcmcia/, and reference it in dmesg in case of hash mismatches. Also add a reference to pcmciautils to Documentation/Changes. With recent changes, you don't need to concern yourself with pcmcia-cs even if you have PCMCIA hardware, so the example above the list needed to be adapted as well. Signed-off-by: Dominik Brodowski <linux@dominikbrodowksi.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation/pcmcia/devicetable.txt')
1 files changed, 64 insertions, 0 deletions
diff --git a/Documentation/pcmcia/devicetable.txt b/Documentation/pcmcia/devicetable.txt
new file mode 100644
index 00000000000..7225f9eddf9
--- /dev/null
+++ b/Documentation/pcmcia/devicetable.txt
@@ -0,0 +1,64 @@
+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:
+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,
+$ ./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;