[MTD] Deal correctly with NOR chips which are smaller than the map window

We used to calculate the number of chips to be zero, allocate an array
of that size, then nasty things would happen when we attempt to access
the first object in that zero-sized array.

Now, if the number of _full_ chips that would fit into the map is zero,
we allocate an array of one anyway, and then artificially reduce the
total size of the resulting MTD device to fit in the map.
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

drivers/mtd/chips/gen_probe.c

@@ -37,8 +37,15 @@ struct mtd_info *mtd_do_chip_probe(struct map_info *map, struct chip_probe *cp)
 	if (!mtd)
 		mtd = check_cmd_set(map, 0); /* Then the secondary */
 
-	if (mtd)
+	if (mtd) {
+		if (mtd->size > map->size) {
+			printk(KERN_WARNING "Reducing visibility of %lKiB chip to %lKiB\n",
+			       (unsigned long)mtd->size >> 10, 
+			       (unsigned long)map->size >> 10);
+			mtd->size = map->size;
+		}
 		return mtd;
+	}
 
 	printk(KERN_WARNING"gen_probe: No supported Vendor Command Set found\n");
 
@@ -100,7 +107,12 @@ static struct cfi_private *genprobe_ident_chips(struct map_info *map, struct chi
 	 * Align bitmap storage size to full byte.
 	 */
 	max_chips = map->size >> cfi.chipshift;
-	mapsize = (max_chips / 8) + ((max_chips % 8) ? 1 : 0);
+	if (!max_chips) {
+		printk(KERN_WARNING "NOR chip too large to fit in mapping. Attempting to cope...\n");
+		max_chips = 1;
+	}
+
+	mapsize = (max_chips + BITS_PER_LONG-1) / BITS_PER_LONG;
 	chip_map = kmalloc(mapsize, GFP_KERNEL);
 	if (!chip_map) {
 		printk(KERN_WARNING "%s: kmalloc failed for CFI chip map\n", map->name);