[SeaBIOS] FDPT not registered when physical == logical ?!

[Kevin O'Connor]

On Mon, Jan 04, 2010 at 12:58:22AM +0100, Samuel Thibault wrote:
> Hello,
> 
> Reading fill_fdpt, I see that when
> nlc == npc && nlh == nph && nlspt == npspt,
> SET_IVT(0x41,etc.) is not done.  Shouldn't it be anyway?

Looks like a bug.

Thanks.
-Kevin


diff --git a/src/block.c b/src/block.c
index c6787e2..01aa84a 100644
--- a/src/block.c
+++ b/src/block.c
@@ -180,20 +180,19 @@ fill_fdpt(struct drive_s *drive_g, int hdid)
     fdpt->heads = nlh;
     fdpt->sectors = nlspt;
 
-    if (nlc == npc && nlh == nph && nlspt == npspt)
-        // no logical CHS mapping used, just physical CHS
-        // use Standard Fixed Disk Parameter Table (FDPT)
-        return;
-
-    // complies with Phoenix style Translated Fixed Disk Parameter
-    // Table (FDPT)
-    fdpt->phys_cylinders = npc;
-    fdpt->phys_heads = nph;
-    fdpt->phys_sectors = npspt;
-    fdpt->a0h_signature = 0xa0;
-
-    // Checksum structure.
-    fdpt->checksum -= checksum(fdpt, sizeof(*fdpt));
+    if (nlc != npc || nlh != nph || nlspt != npspt) {
+        // Logical mapping present - use extended structure.
+
+        // complies with Phoenix style Translated Fixed Disk Parameter
+        // Table (FDPT)
+        fdpt->phys_cylinders = npc;
+        fdpt->phys_heads = nph;
+        fdpt->phys_sectors = npspt;
+        fdpt->a0h_signature = 0xa0;
+
+        // Checksum structure.
+        fdpt->checksum -= checksum(fdpt, sizeof(*fdpt));
+    }
 
     if (hdid == 0)
         SET_IVT(0x41, SEGOFF(get_ebda_seg(), offsetof(