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Don't verify checksum except after serial isolation

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This commit is contained in:
Michael Brown 2005-04-15 13:54:44 +00:00
parent 120192e8d1
commit ab443ba4b0
1 changed files with 7 additions and 10 deletions
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17
src/drivers/bus/isapnp.c
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@ -374,18 +374,15 @@ static int fill_isapnp_device ( struct isapnp_device *isapnp ) {
isapnp_send_key ();
isapnp_wake ( isapnp->csn );
/* Read the identifier and verify the checksum. Allow
* checksum = 0 to cope with cards that just generate the
* checksum using the LFSR during serial isolation.
/* Read the identifier. Do *not* verify the checksum, because
* the PnP ISA spec explicitly states in section 4.5 that the
* checksum is invalid except when read via the serial
* isolation protocol. (This is presumably to allow for lazy
* card designers who implement the checksum using the LFSR
* only and can't be bothered to write the same value into the
* EPROM).
*/
isapnp_peek ( identifier.bytes, sizeof ( identifier ) );
if ( ( identifier.checksum != 0 ) &&
( identifier.checksum != isapnp_checksum ( &identifier ) ) ) {
DBG ( "ISAPnP invalid checksum on CSN %hhx "
"(is %hhx, should be %hhx)\n", isapnp->csn,
identifier.checksum, isapnp_checksum ( &identifier ) );
return 0;
}
/* Read information from identifier structure */
isapnp->vendor_id = identifier.vendor_id;