of: Add memory limiting function for flattened devicetrees

[linux-2.6-block.git] / drivers / of / fdt.c

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index ecc7a02d868e8c52f5b800362fa5ccda0560f775..9aa012e6ea0a6ed988150624bacc0eb2b8066c06 100644 (file)
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -26,6 +26,54 @@
 #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
 #include <asm/page.h>
 
+/*
+ * of_fdt_limit_memory - limit the number of regions in the /memory node
+ * @limit: maximum entries
+ *
+ * Adjust the flattened device tree to have at most 'limit' number of
+ * memory entries in the /memory node. This function may be called
+ * any time after initial_boot_param is set.
+ */
+void of_fdt_limit_memory(int limit)
+{
+       int memory;
+       int len;
+       const void *val;
+       int nr_address_cells = OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
+       int nr_size_cells = OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
+       const uint32_t *addr_prop;
+       const uint32_t *size_prop;
+       int root_offset;
+       int cell_size;
+
+       root_offset = fdt_path_offset(initial_boot_params, "/");
+       if (root_offset < 0)
+               return;
+
+       addr_prop = fdt_getprop(initial_boot_params, root_offset,
+                               "#address-cells", NULL);
+       if (addr_prop)
+               nr_address_cells = fdt32_to_cpu(*addr_prop);
+
+       size_prop = fdt_getprop(initial_boot_params, root_offset,
+                               "#size-cells", NULL);
+       if (size_prop)
+               nr_size_cells = fdt32_to_cpu(*size_prop);
+
+       cell_size = sizeof(uint32_t)*(nr_address_cells + nr_size_cells);
+
+       memory = fdt_path_offset(initial_boot_params, "/memory");
+       if (memory > 0) {
+               val = fdt_getprop(initial_boot_params, memory, "reg", &len);
+               if (len > limit*cell_size) {
+                       len = limit*cell_size;
+                       pr_debug("Limiting number of entries to %d\n", limit);
+                       fdt_setprop(initial_boot_params, memory, "reg", val,
+                                       len);
+               }
+       }
+}
+
 /**
  * of_fdt_is_compatible - Return true if given node from the given blob has
  * compat in its compatible list