* disk/ieee1275/ofdisk.c (grub_ofdisk_iterate): When
	`GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY' flag is set, skip any
	device that doesn't look like an SD card.
	* include/grub/ieee1275/ieee1275.h (grub_ieee1275_flag): Add
	`GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY' flag.
	* kern/powerpc/ieee1275/cmain.c (grub_ieee1275_set_flag): Detect
	OLPC laptop, and set `GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY' when
	found.

diff -urp grub2/disk/ieee1275/ofdisk.c usb/disk/ieee1275/ofdisk.c
--- grub2/disk/ieee1275/ofdisk.c	2008-01-14 05:16:20.000000000 +0100
+++ usb/disk/ieee1275/ofdisk.c	2008-01-20 22:14:55.000000000 +0100
@@ -30,6 +30,33 @@ grub_ofdisk_iterate (int (*hook) (const 
 
   int dev_iterate (struct grub_ieee1275_devalias *alias)
     {
+      grub_dprintf ("disk", "disk name = %s\n", alias->name);
+
+      if (grub_ieee1275_test_flag (GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY))
+	{
+	  grub_ieee1275_phandle_t dev;
+	  char tmp[8];
+
+	  if (grub_ieee1275_finddevice (alias->path, &dev))
+	    {
+	      grub_dprintf ("disk", "finddevice (%s) failed\n", alias->path);
+	      return 0;
+	    }
+
+	  if (grub_ieee1275_get_property (dev, "iconname", tmp,
+					  sizeof tmp, 0))
+	    {
+	      grub_dprintf ("disk", "get iconname failed\n");
+	      return 0;
+	    }
+
+	  if (grub_strcmp (tmp, "sdmmc"))
+	    {
+	      grub_dprintf ("disk", "device is not an SD card\n");
+	      return 0;
+	    }
+	}
+
       if (! grub_strcmp (alias->type, "block"))
 	hook (alias->name);
       else if ((! grub_strcmp (alias->type, "scsi"))
diff -urp grub2/include/grub/ieee1275/ieee1275.h usb/include/grub/ieee1275/ieee1275.h
--- grub2/include/grub/ieee1275/ieee1275.h	2008-01-20 15:08:14.000000000 +0100
+++ usb/include/grub/ieee1275/ieee1275.h	2008-01-20 22:14:55.000000000 +0100
@@ -83,6 +83,9 @@ enum grub_ieee1275_flag
 
   /* CodeGen firmware does not correctly implement "output-device output" */
   GRUB_IEEE1275_FLAG_BROKEN_OUTPUT,
+
+  /* OLPC / XO firmware hangs when accessing USB devices.  */
+  GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY,
 };
 
 extern int EXPORT_FUNC(grub_ieee1275_test_flag) (enum grub_ieee1275_flag flag);
diff -urp grub2/kern/powerpc/ieee1275/cmain.c usb/kern/powerpc/ieee1275/cmain.c
--- grub2/kern/powerpc/ieee1275/cmain.c	2008-01-20 15:08:14.000000000 +0100
+++ usb/kern/powerpc/ieee1275/cmain.c	2008-01-20 22:14:55.000000000 +0100
@@ -49,27 +49,35 @@ grub_ieee1275_set_flag (enum grub_ieee12
 static void
 grub_ieee1275_find_options (void)
 {
+  grub_ieee1275_phandle_t root;
   grub_ieee1275_phandle_t options;
   grub_ieee1275_phandle_t openprom;
   int rc;
   int realmode = 0;
   char tmp[32];
   int is_smartfirmware = 0;
+  int is_olpc = 0;
 
+  grub_ieee1275_finddevice ("/", &root);
   grub_ieee1275_finddevice ("/options", &options);
+  grub_ieee1275_finddevice ("/openprom", &openprom);
+
   rc = grub_ieee1275_get_integer_property (options, "real-mode?", &realmode,
 					   sizeof realmode, 0);
   if (((rc >= 0) && realmode) || (grub_ieee1275_mmu == 0))
     grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_REAL_MODE);
 
-  grub_ieee1275_finddevice ("/openprom", &openprom);
-
   rc = grub_ieee1275_get_property (openprom, "CodeGen-copyright",
 				   tmp,	sizeof (tmp), 0);
 #define SF "SmartFirmware(tm)"
   if (rc >= 0 && !grub_strncmp (tmp, SF, sizeof (SF) - 1))
     is_smartfirmware = 1;
 
+  rc = grub_ieee1275_get_property (root, "architecture",
+				   tmp,	sizeof (tmp), 0);
+  if (rc >= 0 && !grub_strcmp (tmp, "OLPC"))
+    is_olpc = 1;
+
   if (is_smartfirmware)
     {
       /* Broken in all versions */
@@ -101,6 +109,30 @@ grub_ieee1275_find_options (void)
 	    }
 	}
     }
+
+  if (is_olpc)
+    {
+      /* OLPC / XO laptops have three kinds of storage devices:
+
+	 - NAND flash.  These are accessible via OFW callbacks, but:
+	   - Follow strange semantics, imposed by hardware constraints.
+	   - Its ABI is undocumented, and not stable.
+	   They lack "device_type" property, which conveniently makes GRUB
+	   skip them.
+
+	 - USB drives.  Not accessible, because OFW shuts down the controller
+	   in order to prevent collisions with applications accessing it
+	   directly.  Even worse, attempts to access it will NOT return
+	   control to the caller, so we have to avoid probing them.
+
+	 - SD cards.  These work fine.
+
+	 To avoid brekage, we only need to skip USB probing.  However,
+	 since detecting SD cards is more reliable, we do that instead.
+      */
+
+      grub_ieee1275_set_flag (GRUB_IEEE1275_FLAG_OFDISK_SDCARD_ONLY);
+    }
 }
 
 void cmain (void);