linux/Documentation/pcmcia/devicetable.txt
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   1Matching of PCMCIA devices to drivers is done using one or more of the
   2following criteria:
   3
   4- manufactor ID
   5- card ID
   6- product ID strings _and_ hashes of these strings
   7- function ID
   8- device function (actual and pseudo)
   9
  10You should use the helpers in include/pcmcia/device_id.h for generating the
  11struct pcmcia_device_id[] entries which match devices to drivers.
  12
  13If you want to match product ID strings, you also need to pass the crc32
  14hashes of the string to the macro, e.g. if you want to match the product ID
  15string 1, you need to use
  16
  17PCMCIA_DEVICE_PROD_ID1("some_string", 0x(hash_of_some_string)),
  18
  19If the hash is incorrect, the kernel will inform you about this in "dmesg"
  20upon module initialization, and tell you of the correct hash.
  21
  22You can determine the hash of the product ID strings by catting the file
  23"modalias" in the sysfs directory of the PCMCIA device. It generates a string
  24in the following form:
  25pcmcia:m0149cC1ABf06pfn00fn00pa725B842DpbF1EFEE84pc0877B627pd00000000
  26
  27The hex value after "pa" is the hash of product ID string 1, after "pb" for
  28string 2 and so on.
  29
  30Alternatively, you can use crc32hash (see Documentation/pcmcia/crc32hash.c)
  31to determine the crc32 hash.  Simply pass the string you want to evaluate
  32as argument to this program, e.g.:
  33$ ./crc32hash "Dual Speed"
  34
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