Changeset 77392 in vbox for trunk/src/VBox/Devices/Storage

Timestamp:

Feb 20, 2019 4:05:10 PM (6 years ago)

Author:

vboxsync

Message:

DevATA: Return bit 7 clear when reading registers on IDE channel with no drives. Avoids 2x35s delay with EFI IDE device detection. See bugref:5869

File:

• trunk/src/VBox/Devices/Storage/DevATA.cpp (modified) (1 diff)

trunk/src/VBox/Devices/Storage/DevATA.cpp

@@ -4493 +4493 @@
         else                    /* Device 0 selected (but not present). */
         {
-            Log2(("%s: addr=%#x: LUN#%d not attached\n", __FUNCTION__, addr, s->iLUN));
-            return VERR_IOM_IOPORT_UNUSED;
+            /* ATA-3 and later specifies that the host must have a pull-down resistor on DD7; ATA-5 explains
+             * that this causes the BSY bit to always be read as clear when there is no device on a given
+             * channel. Software then does not need to wait a long time for non-existent drives; note that
+             * EFI (TianoCore) relies on this behavior.
+             */
+            *pu32 = 0x7F;
+            Log2(("%s: addr=%#x: LUN#%d not attached, val=%#02x\n", __FUNCTION__, addr, s->iLUN, *pu32));
+            return VINF_SUCCESS;
         }
     }