Do not allow duplicate IDs in video mode info buffer.

Modes are returned in a buffer from qemu with IDs in increasing but not
necessarily consecutive order. (Some modes may be omitted if they don't fit
into the framebuffer.) Two custom modes are appended to the local buffer to
support arbitrary resolutions. The first custom id must be set to +1 of the
last id in the mode buffer, not to the last index +1 of the buffer.

E.G. these are the last entries in the mode buffer returned from QEMU:
	Index      Mode id (unfortunately named ModeIndex in the struct)
	...
	124         128
	125         130
	126         132
	127         134 (last mode returned from QEMU)

Custom Modes:
	128         135 (Not 128!)
	129         136

If the first custom mode id is set to 128 (the number of modes returned
from QEMU), it will duplicate the id for the mode at index 124. That could
cause the FindMode function which searches the mode list by mode id
to return the wrong mode information.

The custom mode id's are now set to be greater than the last mode id
returned from QEMU.

The last argument in the FillVidModeInfo is replaced with the actual mode
id rather than the index.  This does nothing more than replace the mode id
with itself.

This addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1202424

---
Updated the comments
---

1 files changed, 11 insertions, 4 deletions

diff --git a/xddm/miniport/qxl.c b/xddm/miniport/qxl.c
index e0fb87f..22537e2 100644
--- a/xddm/miniport/qxl.c
+++ b/xddm/miniport/qxl.c
@@ -596,6 +596,7 @@ VP_STATUS InitModes(QXLExtension *dev)
     ULONG n_modes;
     ULONG i;
     VP_STATUS error;
+    ULONG custom_mode_id = 0;
 
     PAGED_CODE();
     DEBUG_PRINT((dev, 0, "%s\n", __FUNCTION__));
@@ -632,6 +633,11 @@ VP_STATUS InitModes(QXLExtension *dev)
             return error;
         }
     }
+    /*  Mode ids are increasing in the buffer but may not be consecutive,
+     *  so set the first custom id to be 1 larger than the last id in the buffer.
+     *  (ModeIndex isn't really an index, it is an ID).
+     */
+    custom_mode_id = modes->modes[modes->n_modes-1].id + 1;
 
     /* 2 dummy modes for custom display resolution */
     /* This is necessary to bypass Windows mode index check, that
@@ -640,7 +646,7 @@ VP_STATUS InitModes(QXLExtension *dev)
 
     for (i = dev->custom_mode; i <= dev->custom_mode + 1; ++i) {
         memcpy(&modes_info[i], &modes_info[0], sizeof(VIDEO_MODE_INFORMATION));
-        modes_info[i].ModeIndex = i;
+        modes_info[i].ModeIndex = custom_mode_id++;
     }
 
     dev->n_modes = n_modes;
@@ -1002,6 +1008,7 @@ static VP_STATUS SetCustomDisplay(QXLExtension *dev_ext, QXLEscapeSetCustomDispl
     uint32_t xres = custom_display->xres;
     uint32_t yres = custom_display->yres;
     uint32_t bpp = custom_display->bpp;
+    PVIDEO_MODE_INFORMATION pMode;
 
     /* alternate custom mode index */
     if (dev_ext->custom_mode == (dev_ext->n_modes - 1))
@@ -1014,11 +1021,11 @@ static VP_STATUS SetCustomDisplay(QXLExtension *dev_ext, QXLEscapeSetCustomDispl
                     __FUNCTION__, xres, yres, bpp, dev_ext->rom->surface0_area_size));
         return ERROR_NOT_ENOUGH_MEMORY;
     }
-
-    ret = FillVidModeInfo(&dev_ext->modes[dev_ext->custom_mode],
+    pMode = &dev_ext->modes[dev_ext->custom_mode];
+    ret = FillVidModeInfo(pMode,
                           custom_display->xres, custom_display->yres,
                           custom_display->bpp,
-                          dev_ext->custom_mode);
+                          pMode->ModeIndex);
     DEBUG_PRINT((dev_ext, 0, "%s: Returning %d\n", __FUNCTION__, ret));
     return ret;
 }