dma_addr_t page_table_bus;
 };
 
+#define SBP2_ROM_VALUE_WILDCARD ~0         /* match all */
+#define SBP2_ROM_VALUE_MISSING  0xff000000 /* not present in the unit dir. */
+
 /*
  * List of devices with known bugs.
  *
  * The firmware_revision field, masked with 0xffff00, is the best
  * indicator for the type of bridge chip of a device.  It yields a few
  * false positives but this did not break correctly behaving devices
- * so far.  We use ~0 as a wildcard, since the 24 bit values we get
- * from the config rom can never match that.
+ * so far.
  */
 static const struct {
        u32 firmware_revision;
        },
        /* Initio bridges, actually only needed for some older ones */ {
                .firmware_revision      = 0x000200,
-               .model                  = ~0,
+               .model                  = SBP2_ROM_VALUE_WILDCARD,
                .workarounds            = SBP2_WORKAROUND_INQUIRY_36,
        },
        /* PL-3507 bridge with Prolific firmware */ {
                .firmware_revision      = 0x012800,
-               .model                  = ~0,
+               .model                  = SBP2_ROM_VALUE_WILDCARD,
                .workarounds            = SBP2_WORKAROUND_POWER_CONDITION,
        },
        /* Symbios bridge */ {
                .firmware_revision      = 0xa0b800,
-               .model                  = ~0,
+               .model                  = SBP2_ROM_VALUE_WILDCARD,
                .workarounds            = SBP2_WORKAROUND_128K_MAX_TRANS,
        },
        /* Datafab MD2-FW2 with Symbios/LSILogic SYM13FW500 bridge */ {
                .firmware_revision      = 0x002600,
-               .model                  = ~0,
+               .model                  = SBP2_ROM_VALUE_WILDCARD,
                .workarounds            = SBP2_WORKAROUND_128K_MAX_TRANS,
        },
 
                        continue;
 
                if (sbp2_workarounds_table[i].model != model &&
-                   sbp2_workarounds_table[i].model != ~0)
+                   sbp2_workarounds_table[i].model != SBP2_ROM_VALUE_WILDCARD)
                        continue;
 
                w |= sbp2_workarounds_table[i].workarounds;
        fw_device_get(device);
        fw_unit_get(unit);
 
-       /* Initialize to values that won't match anything in our table. */
-       firmware_revision = 0xff000000;
-       model = 0xff000000;
-
        /* implicit directory ID */
        tgt->directory_id = ((unit->directory - device->config_rom) * 4
                             + CSR_CONFIG_ROM) & 0xffffff;
 
+       firmware_revision = SBP2_ROM_VALUE_MISSING;
+       model             = SBP2_ROM_VALUE_MISSING;
+
        if (sbp2_scan_unit_dir(tgt, unit->directory, &model,
                               &firmware_revision) < 0)
                goto fail_tgt_put;