2 files changed, 86 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index 26590ab..d8f7a09 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,8 @@
 - monitor-get-edid-using-vbe:
   o update x86emu from xserver git (fixes issues at least with newish
     NVIDIA cards)
+  o check if the port supports DDC before trying to read EDID data (this
+    should prevent problems when probing nonexistent ports on old cards)
 
 Version 2.2 - 16 August 2009
 
diff --git a/vbe.c b/vbe.c
index 7791751..ff02e03 100644
--- a/vbe.c
+++ b/vbe.c
@@ -135,6 +135,42 @@ static int vbe_check_vbe_info(hd_data_t *hd_data)
   return 1;
 }
 
+static void parse_ddc_info(int port, int info)
+{
+  log_err("Port %d:\n", port);
+  log_err("  DDC1 %ssupported\n", info & 1 ? "" : "not ");
+  log_err("  DDC2 %ssupported\n", info & 2 ? "" : "not ");
+  log_err("  Screen %sblanked during data transfer\n", info & 4 ? "" : "not ");
+  log_err("  Time to transfer one EDID block: %d sec (rounded up)\n", (info & 0xff00) >> 8);
+}
+
+static int vbe_check_ddc_capabilities(hd_data_t *hd_data, int port)
+{
+  int i;
+  int ax, bx, cx;
+
+  /* Setup registers for the interrupt call */
+  ax = 0x4f15;
+  bx = 0; /* Report DDC Capabilities */
+  cx = port;
+
+  /* Get capabilities */
+  i = CallInt10(&ax, &bx, &cx, NULL, 0, hd_data->flags.cpuemu) & 0xffff;
+  if (i != 0x4f) {
+    log_err("DDC: Error (0x4f15:00): 0x%04x\n", i);
+    return 0;
+  }
+
+  parse_ddc_info(port, bx);
+
+  if (!(bx & 3)) {
+    log_err("DDC (0x4f15:00): DDC not supported, not continuing\n", i);
+    return 0;
+  }
+
+  return 1;
+}
+
 /* Get EDID info. */
 int vbe_get_edid_info(hd_data_t *hd_data, char *edid, int port)
 {
@@ -149,7 +185,7 @@ int vbe_get_edid_info(hd_data_t *hd_data, char *edid, int port)
   /* Get EDID block */
   i = CallInt10(&ax, &bx, &cx, edid, 256, hd_data->flags.cpuemu) & 0xffff;
   if (i != 0x4f) {
-    log_err("EDID: Error (0x4f15): 0x%04x\n", i);
+    log_err("EDID: Error (0x4f15:01): 0x%04x\n", i);
     return 0;
   }
 
@@ -211,6 +247,49 @@ static int vbe_check_vbe_info__old(void)
   return 1;
 }
 
+static int vbe_check_ddc_capabilities__old(int port)
+{
+  int i;
+  struct LRMI_regs regs;
+
+  /* initialize LRMI */
+  if (LRMI_init() == 0) {
+    log_err("EDID: could not initialize LRMI\n");
+    return 0;
+  }
+
+  /* set up registers for the interrupt call. */
+  memset(&regs, 0, sizeof(regs));
+  regs.eax = 0x4f15;
+  regs.ebx = 0x0000;
+  regs.ecx = port;
+  regs.es = 0;
+  regs.edi = 0;
+
+  /* do it. */
+  iopl(3);
+  ioperm(0, 0x400, 1);
+  if (LRMI_int(0x10, &regs) == 0) {
+    return 0;
+  }
+
+  /* check for successful return code */
+  i = regs.eax & 0xffff;
+  if (i != 0x4f) {
+    log_err("DDC: Error (0x4f15:00): 0x%04x\n", i);
+    return 0;
+  }
+
+  parse_ddc_info(port, regs.ebx);
+
+  if (!(regs.ebx & 3)) {
+    log_err("DDC (0x4f15:00): DDC not supported, not continuing\n", i);
+    return 0;
+  }
+
+  return 1;
+}
+
 static int vbe_get_edid_info__old(char *edid, int port)
 {
   int i;
@@ -252,7 +331,7 @@ static int vbe_get_edid_info__old(char *edid, int port)
   i = regs.eax & 0xffff;
   if (i != 0x4f) {
     LRMI_free_real(mem);
-    log_err("EDID: Error (0x4f15): 0x%04x\n", i);
+    log_err("EDID: Error (0x4f15:01): 0x%04x\n", i);
     return 0;
   }
 
@@ -269,7 +348,8 @@ int get_edid__old(char *edid, int port)
      one is also bogus for the other */
   log_err("Retrying with old LRMI interface\n");
   ok = 
-    (box_is_xbox() || vbe_check_vbe_info__old()) &&
+    (box_is_xbox() || (vbe_check_vbe_info__old() &&
+     vbe_check_ddc_capabilities__old(port))) &&
     vbe_get_edid_info__old(edid, port);
   return ok;
 }
@@ -287,6 +367,7 @@ int get_edid(hd_data_t *hd_data, char *edid, int port)
   if (!box_is_xbox()) {
 	if (InitInt10(hd_data) == 0) {
 	  ok = vbe_check_vbe_info(hd_data)
+		&& vbe_check_ddc_capabilities(hd_data, port)
 		&& vbe_get_edid_info(hd_data, edid, port);
 	  FreeInt10();
 	}