fdt_support: Add helper function to read "ranges" property
This patch adds a helper function that can be used to interpret most
"ranges" properties in the device tree.
It reads the n'th range out of a "ranges" array and returns the node's
virtual address of the range, the physical address that range starts at
and the size of the range.
Signed-off-by: Alexander Graf <agraf@suse.de>
Acked-by: Scott Wood <scottwood@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/common/fdt_support.c b/common/fdt_support.c
index cc0bf76..fcd2523 100644
--- a/common/fdt_support.c
+++ b/common/fdt_support.c
@@ -1435,3 +1435,97 @@
return prop ? fdt_translate_address(fdt, node, prop + naddr) : 0;
}
+
+/*
+ * Read a property of size <prop_len>. Currently only supports 1 or 2 cells.
+ */
+static int fdt_read_prop(const fdt32_t *prop, int prop_len, int cell_off,
+ uint64_t *val, int cells)
+{
+ const fdt32_t *prop32 = &prop[cell_off];
+ const fdt64_t *prop64 = (const fdt64_t *)&prop[cell_off];
+
+ if ((cell_off + cells) > prop_len)
+ return -FDT_ERR_NOSPACE;
+
+ switch (cells) {
+ case 1:
+ *val = fdt32_to_cpu(*prop32);
+ break;
+ case 2:
+ *val = fdt64_to_cpu(*prop64);
+ break;
+ default:
+ return -FDT_ERR_NOSPACE;
+ }
+
+ return 0;
+}
+
+/**
+ * fdt_read_range - Read a node's n'th range property
+ *
+ * @fdt: ptr to device tree
+ * @node: offset of node
+ * @n: range index
+ * @child_addr: pointer to storage for the "child address" field
+ * @addr: pointer to storage for the CPU view translated physical start
+ * @len: pointer to storage for the range length
+ *
+ * Convenience function that reads and interprets a specific range out of
+ * a number of the "ranges" property array.
+ */
+int fdt_read_range(void *fdt, int node, int n, uint64_t *child_addr,
+ uint64_t *addr, uint64_t *len)
+{
+ int pnode = fdt_parent_offset(fdt, node);
+ const fdt32_t *ranges;
+ int pacells;
+ int acells;
+ int scells;
+ int ranges_len;
+ int cell = 0;
+ int r = 0;
+
+ /*
+ * The "ranges" property is an array of
+ * { <child address> <parent address> <size in child address space> }
+ *
+ * All 3 elements can span a diffent number of cells. Fetch their size.
+ */
+ pacells = fdt_getprop_u32_default_node(fdt, pnode, 0, "#address-cells", 1);
+ acells = fdt_getprop_u32_default_node(fdt, node, 0, "#address-cells", 1);
+ scells = fdt_getprop_u32_default_node(fdt, node, 0, "#size-cells", 1);
+
+ /* Now try to get the ranges property */
+ ranges = fdt_getprop(fdt, node, "ranges", &ranges_len);
+ if (!ranges)
+ return -FDT_ERR_NOTFOUND;
+ ranges_len /= sizeof(uint32_t);
+
+ /* Jump to the n'th entry */
+ cell = n * (pacells + acells + scells);
+
+ /* Read <child address> */
+ if (child_addr) {
+ r = fdt_read_prop(ranges, ranges_len, cell, child_addr,
+ acells);
+ if (r)
+ return r;
+ }
+ cell += acells;
+
+ /* Read <parent address> */
+ if (addr)
+ *addr = fdt_translate_address(fdt, node, ranges + cell);
+ cell += pacells;
+
+ /* Read <size in child address space> */
+ if (len) {
+ r = fdt_read_prop(ranges, ranges_len, cell, len, scells);
+ if (r)
+ return r;
+ }
+
+ return 0;
+}
diff --git a/include/fdt_support.h b/include/fdt_support.h
index 61383dd..b77a0f1 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -87,6 +87,8 @@
int fdt_verify_alias_address(void *fdt, int anode, const char *alias,
u64 addr);
u64 fdt_get_base_address(void *fdt, int node);
+int fdt_read_range(void *fdt, int node, int n, uint64_t *child_addr,
+ uint64_t *addr, uint64_t *len);
enum fdt_status {
FDT_STATUS_OKAY,