Improved debugging output

src/drivers/bus/isa.c

 	/* Iterate through any ISA probe addresses specified by
 	 * config.c, starting where we left off.
 	 */
+	DBG ( "ISA searching for device matching driver %s\n", driver->name );
 	for ( i = isa->probe_idx ; i < isa_extra_probe_addr_count ; i++ ) {
 		/* If we've already used this device, skip it */
 		if ( isa->already_tried ) {
 
  notfound:
 	/* No device found */
+	DBG ( "ISA found no device matching driver %s\n", driver->name );
 	isa->probe_idx = 0;
 	return 0;
 

src/drivers/bus/isapnp.c

 	/* Iterate through all possible ISAPNP CSNs, starting where we
 	 * left off.
 	 */
+	DBG ( "ISAPnP searching for device matching driver %s\n",
+	      driver->name );
 	for ( ; isapnp->csn <= isapnp_max_csn ; isapnp->csn++ ) {
 		for ( ; isapnp->logdev <= 0xff ; isapnp->logdev++ ) {
 			/* If we've already used this device, skip it */
 				if ( ( isapnp->vendor_id == id->vendor_id ) &&
 				     ( ISA_PROD_ID ( isapnp->prod_id ) ==
 				       ISA_PROD_ID ( id->prod_id ) ) ) {
-					DBG ( "Device %s (driver %s) "
-					      "matches ID %s\n",
-					      id->name, driver->name,
+					DBG ( "ISAPnP found ID %hx:%hx "
+					      "(\"%s\") (device %s) "
+					      "matching driver %s\n",
+					      isapnp->vendor_id,
+					      isapnp->prod_id,
 					      isa_id_string( isapnp->vendor_id,
-							   isapnp->prod_id ) );
+							     isapnp->prod_id ),
+					      id->name, driver->name );
 					isapnp->name = id->name;
 					isapnp->already_tried = 1;
 					return 1;
 	}
 
 	/* No device found */
+	DBG ( "ISAPnP found no device matching driver %s\n", driver->name );
 	isapnp->csn = 1;
 	return 0;
 }

src/drivers/bus/mca.c

  *
  */
 static int fill_mca_device ( struct mca_device *mca ) {
-	unsigned int i;
+	unsigned int i, seen_non_ff;
 
 	/* Make sure motherboard setup is off */
 	outb_p ( 0xff, MCA_MOTHERBOARD_SETUP_REG );
 	outb_p ( 0x8 | ( mca->slot & 0xf ), MCA_ADAPTER_SETUP_REG );
 
 	/* Read the POS registers */
+	seen_non_ff = 0;
 	for ( i = 0 ; i < ( sizeof ( mca->pos ) / sizeof ( mca->pos[0] ) ) ;
 	      i++ ) {
 		mca->pos[i] = inb_p ( MCA_POS_REG ( i ) );
+		if ( mca->pos[i] != 0xff )
+			seen_non_ff = 1;
 	}
+	
+	/* If all POS registers are 0xff, this means there's no device
+	 * present
+	 */
+	if ( ! seen_non_ff )
+		return 0;
 
 	/* Kill all setup modes */
 	outb_p ( 0, MCA_ADAPTER_SETUP_REG );
 	/* Iterate through all possible MCA slots, starting where we
 	 * left off
 	 */
+	DBG ( "MCA searching for device matching driver %s\n", driver->name );
 	for ( ; mca->slot < MCA_MAX_SLOT_NR ; mca->slot++ ) {
 		/* If we've already used this device, skip it */
 		if ( mca->already_tried ) {
 			struct mca_id *id = &driver->ids[i];
 
 			if ( MCA_ID ( mca ) == id->id ) {
-				DBG ( "Device %s (driver %s) matches ID %hx\n",
-				      id->name, driver->name, id->id );
+				DBG ( "MCA found ID %hx (device %s) "
+				      "matching driver %s\n",
+				      id->name, id->id, driver->name );
 				mca->name = id->name;
 				mca->already_tried = 1;
 				return 1;
 	}
 
 	/* No device found */
+	DBG ( "MCA found no device matching driver %s\n", driver->name );
 	mca->slot = 0;
 	return 0;
 }