libfdt: Add overlay application function

The device tree overlays are a good way to deal with user-modifyable
boards or boards with some kind of an expansion mechanism where we can
easily plug new board in (like the BBB, the Raspberry Pi or the CHIP).

Add a new function to merge overlays with a base device tree.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

diff --git a/include/libfdt.h b/include/libfdt.h
index 4c56711c7132943b8ff0dcea8f68dd21265a1860..b6a400a7a823ea2bd6a04e6fe3bbe7807a2252bb 100644 (file)
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -1740,6 +1740,36 @@ int fdt_add_subnode(void *fdt, int parentoffset, const char *name);
  */
 int fdt_del_node(void *fdt, int nodeoffset);
 
+/**
+ * fdt_overlay_apply - Applies a DT overlay on a base DT
+ * @fdt: pointer to the base device tree blob
+ * @fdto: pointer to the device tree overlay blob
+ *
+ * fdt_overlay_apply() will apply the given device tree overlay on the
+ * given base device tree.
+ *
+ * Expect the base device tree to be modified, even if the function
+ * returns an error.
+ *
+ * returns:
+ *     0, on success
+ *     -FDT_ERR_NOSPACE, there's not enough space in the base device tree
+ *     -FDT_ERR_NOTFOUND, the overlay points to some inexistant nodes or
+ *             properties in the base DT
+ *     -FDT_ERR_BADPHANDLE, the phandles in the overlay do not have the right
+ *             magic
+ *     -FDT_ERR_INTERNAL,
+ *     -FDT_ERR_BADLAYOUT,
+ *     -FDT_ERR_BADMAGIC,
+ *     -FDT_ERR_BADOFFSET,
+ *     -FDT_ERR_BADPATH,
+ *     -FDT_ERR_BADVERSION,
+ *     -FDT_ERR_BADSTRUCTURE,
+ *     -FDT_ERR_BADSTATE,
+ *     -FDT_ERR_TRUNCATED, standard meanings
+ */
+int fdt_overlay_apply(void *fdt, void *fdto);
+
 /**********************************************************************/
 /* Debugging / informational functions                                */
 /**********************************************************************/

diff --git a/lib/Kconfig b/lib/Kconfig
index 02ca4058d37e0b4e7f23b9885e9cc051d292c0ec..16ff01a2cd37490e131924bf6c0d04b5f88823d0 100644 (file)
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -139,6 +139,11 @@ config OF_LIBFDT
          particular compatible nodes. The library operates on a flattened
          version of the device tree.
 
+config OF_LIBFDT_OVERLAY
+       bool "Enable the FDT library overlay support"
+       help
+         This enables the FDT library (libfdt) overlay support.
+
 config SPL_OF_LIBFDT
        bool "Enable the FDT library for SPL"
        default y if SPL_OF_CONTROL

diff --git a/lib/libfdt/Makefile b/lib/libfdt/Makefile
index 8b86c15904cbf8c7ba5f3f35a5d673f38a4d0b02..6ef8290f4e09a0cda981db10427084dcd6d4be9a 100644 (file)
--- a/lib/libfdt/Makefile
+++ b/lib/libfdt/Makefile
@@ -15,3 +15,5 @@ obj-y += \
        fdt_empty_tree.o \
        fdt_addresses.o \
        fdt_region.o
+
+obj-$(CONFIG_OF_LIBFDT_OVERLAY) += fdt_overlay.o

diff --git a/lib/libfdt/fdt_overlay.c b/lib/libfdt/fdt_overlay.c
new file mode 100644 (file)
index 0000000..c45e8b2
--- /dev/null
+++ b/lib/libfdt/fdt_overlay.c
@@ -0,0 +1,405 @@
+#include "libfdt_env.h"
+
+#include <fdt.h>
+#include <libfdt.h>
+
+#include "libfdt_internal.h"
+
+static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
+{
+       const uint32_t *val;
+       int len;
+
+       val = fdt_getprop(fdto, fragment, "target", &len);
+       if (!val)
+               return 0;
+
+       if ((*val == 0xffffffff) || (len != sizeof(*val)))
+               return 0xffffffff;
+
+       return fdt32_to_cpu(*val);
+}
+
+static int overlay_get_target(const void *fdt, const void *fdto,
+                             int fragment)
+{
+       uint32_t phandle;
+       const char *path;
+
+       /* Try first to do a phandle based lookup */
+       phandle = overlay_get_target_phandle(fdto, fragment);
+       if (phandle == -1)
+               return -FDT_ERR_BADPHANDLE;
+
+       if (phandle)
+               return fdt_node_offset_by_phandle(fdt, phandle);
+
+       /* And then a path based lookup */
+       path = fdt_getprop(fdto, fragment, "target-path", NULL);
+       if (!path)
+               return -FDT_ERR_NOTFOUND;
+
+       return fdt_path_offset(fdt, path);
+}
+
+static int overlay_phandle_add_offset(void *fdt, int node,
+                                     const char *name, uint32_t delta)
+{
+       const uint32_t *val;
+       uint32_t adj_val;
+       int len;
+
+       val = fdt_getprop(fdt, node, name, &len);
+       if (!val)
+               return len;
+
+       if (len != sizeof(*val))
+               return -FDT_ERR_BADSTRUCTURE;
+
+       adj_val = fdt32_to_cpu(*val);
+       if ((adj_val + delta) < adj_val)
+               return -FDT_ERR_BADPHANDLE;
+
+       adj_val += delta;
+       return fdt_setprop_inplace_u32(fdt, node, name, adj_val);
+}
+
+static int overlay_adjust_node_phandles(void *fdto, int node,
+                                       uint32_t delta)
+{
+       bool found = false;
+       int child;
+       int ret;
+
+       ret = overlay_phandle_add_offset(fdto, node, "phandle", delta);
+       if (ret && ret != -FDT_ERR_NOTFOUND)
+               return ret;
+
+       if (!ret)
+               found = true;
+
+       ret = overlay_phandle_add_offset(fdto, node, "linux,phandle", delta);
+       if (ret && ret != -FDT_ERR_NOTFOUND)
+               return ret;
+
+       /*
+        * If neither phandle nor linux,phandle have been found return
+        * an error.
+        */
+       if (!found && !ret)
+               return ret;
+
+       fdt_for_each_subnode(fdto, child, node)
+               overlay_adjust_node_phandles(fdto, child, delta);
+
+       return 0;
+}
+
+static int overlay_adjust_local_phandles(void *fdto, uint32_t delta)
+{
+       /*
+        * Start adjusting the phandles from the overlay root
+        */
+       return overlay_adjust_node_phandles(fdto, 0, delta);
+}
+
+static int overlay_update_local_node_references(void *fdto,
+                                               int tree_node,
+                                               int fixup_node,
+                                               uint32_t delta)
+{
+       int fixup_prop;
+       int fixup_child;
+       int ret;
+
+       fdt_for_each_property_offset(fixup_prop, fdto, fixup_node) {
+               const uint32_t *val = NULL;
+               uint32_t adj_val, index;
+               const char *name;
+               int fixup_len;
+               int tree_len;
+
+               val = fdt_getprop_by_offset(fdto, fixup_prop,
+                                           &name, &fixup_len);
+               if (!val)
+                       return fixup_len;
+               index = fdt32_to_cpu(*val);
+
+               val = fdt_getprop(fdto, tree_node, name, &tree_len);
+               if (!val)
+                       return tree_len;
+
+               /*
+                * The index can be unaligned.
+                *
+                * Use a memcpy for the architectures that do not
+                * support unaligned accesses.
+                */
+               memcpy(&adj_val, (unsigned char *)val + index,
+                      sizeof(uint32_t));
+
+               adj_val = fdt32_to_cpu(adj_val);
+               adj_val += delta;
+               adj_val = cpu_to_fdt32(adj_val);
+
+               ret = fdt_setprop_inplace_namelen_by_index(fdto, tree_node,
+                                                          name, strlen(name),
+                                                          index, &adj_val,
+                                                          sizeof(adj_val));
+               if (ret)
+                       return ret;
+       }
+
+       fdt_for_each_subnode(fdto, fixup_child, fixup_node) {
+               const char *fixup_child_name = fdt_get_name(fdto, fixup_child,
+                                                           NULL);
+               int tree_child;
+
+               tree_child = fdt_subnode_offset(fdto, tree_node,
+                                               fixup_child_name);
+               if (tree_child < 0)
+                       return tree_child;
+
+               ret = overlay_update_local_node_references(fdto,
+                                                          tree_child,
+                                                          fixup_child,
+                                                          delta);
+               if (ret)
+                       return ret;
+       }
+
+       return 0;
+}
+
+static int overlay_update_local_references(void *dto, uint32_t delta)
+{
+       int fixups;
+
+       fixups = fdt_path_offset(dto, "/__local_fixups__");
+       if (fixups < 0) {
+               /* There's no local phandles to adjust, bail out */
+               if (fixups == -FDT_ERR_NOTFOUND)
+                       return 0;
+
+               return fixups;
+       }
+
+       /*
+        * Update our local references from the root of the tree
+        */
+       return overlay_update_local_node_references(dto, 0, fixups,
+                                                   delta);
+}
+
+static int overlay_fixup_one_phandle(void *fdt, void *fdto,
+                                    int symbols_off,
+                                    const char *path, uint32_t path_len,
+                                    const char *name, uint32_t name_len,
+                                    int index, const char *label)
+{
+       const char *symbol_path;
+       uint32_t phandle;
+       int symbol_off, fixup_off;
+       int prop_len;
+
+       symbol_path = fdt_getprop(fdt, symbols_off, label,
+                                 &prop_len);
+       if (!symbol_path)
+               return -FDT_ERR_NOTFOUND;
+
+       symbol_off = fdt_path_offset(fdt, symbol_path);
+       if (symbol_off < 0)
+               return symbol_off;
+
+       phandle = fdt_get_phandle(fdt, symbol_off);
+       if (!phandle)
+               return -FDT_ERR_NOTFOUND;
+
+       fixup_off = fdt_path_offset_namelen(fdto, path, path_len);
+       if (fixup_off < 0)
+               return fixup_off;
+
+       phandle = cpu_to_fdt32(phandle);
+       return fdt_setprop_inplace_namelen_by_index(fdto, fixup_off,
+                                                   name, name_len, index,
+                                                   &phandle, sizeof(phandle));
+};
+
+static int overlay_fixup_phandle(void *fdt, void *fdto, int symbols_off,
+                                int property)
+{
+       const char *value;
+       const char *label;
+       int len;
+
+       value = fdt_getprop_by_offset(fdto, property,
+                                     &label, &len);
+       if (!value)
+               return len;
+
+       do {
+               const char *prop_string = value;
+               const char *path, *name;
+               uint32_t prop_len = strlen(value);
+               uint32_t path_len, name_len;
+               char *sep, *endptr;
+               int index;
+               int ret;
+
+               path = prop_string;
+               sep = memchr(prop_string, ':', prop_len);
+               if (*sep != ':')
+                       return -FDT_ERR_BADSTRUCTURE;
+               path_len = sep - path;
+
+               name = sep + 1;
+               sep = memchr(name, ':', prop_len);
+               if (*sep != ':')
+                       return -FDT_ERR_BADSTRUCTURE;
+               name_len = sep - name;
+
+               index = strtoul(sep + 1, &endptr, 10);
+               if ((*endptr != '\0') || (endptr <= (sep + 1)))
+                       return -FDT_ERR_BADSTRUCTURE;
+
+               len -= prop_len + 1;
+               value += prop_len + 1;
+
+               ret = overlay_fixup_one_phandle(fdt, fdto, symbols_off,
+                                               path, path_len, name, name_len,
+                                               index, label);
+               if (ret)
+                       return ret;
+       } while (len > 0);
+
+       return 0;
+}
+
+static int overlay_fixup_phandles(void *dt, void *dto)
+{
+       int fixups_off, symbols_off;
+       int property;
+
+       symbols_off = fdt_path_offset(dt, "/__symbols__");
+       fixups_off = fdt_path_offset(dto, "/__fixups__");
+
+       fdt_for_each_property_offset(property, dto, fixups_off)
+               overlay_fixup_phandle(dt, dto, symbols_off, property);
+
+       return 0;
+}
+
+static int apply_overlay_node(void *dt, int target,
+                             void *dto, int fragment)
+{
+       int property;
+       int node;
+
+       fdt_for_each_property_offset(property, dto, fragment) {
+               const char *name;
+               const void *prop;
+               int prop_len;
+               int ret;
+
+               prop = fdt_getprop_by_offset(dto, property, &name,
+                                            &prop_len);
+               if (prop_len == -FDT_ERR_NOTFOUND)
+                       return -FDT_ERR_INTERNAL;
+               if (prop_len < 0)
+                       return prop_len;
+
+               ret = fdt_setprop(dt, target, name, prop, prop_len);
+               if (ret)
+                       return ret;
+       }
+
+       fdt_for_each_subnode(dto, node, fragment) {
+               const char *name = fdt_get_name(dto, node, NULL);
+               int nnode;
+               int ret;
+
+               nnode = fdt_add_subnode(dt, target, name);
+               if (nnode == -FDT_ERR_EXISTS)
+                       nnode = fdt_subnode_offset(dt, target, name);
+
+               if (nnode < 0)
+                       return nnode;
+
+               ret = apply_overlay_node(dt, nnode, dto, node);
+               if (ret)
+                       return ret;
+       }
+
+       return 0;
+}
+
+static int overlay_merge(void *dt, void *dto)
+{
+       int fragment;
+
+       fdt_for_each_subnode(dto, fragment, 0) {
+               int overlay;
+               int target;
+               int ret;
+
+               target = overlay_get_target(dt, dto, fragment);
+               if (target < 0)
+                       continue;
+
+               overlay = fdt_subnode_offset(dto, fragment, "__overlay__");
+               if (overlay < 0)
+                       return overlay;
+
+               ret = apply_overlay_node(dt, target, dto, overlay);
+               if (ret)
+                       return ret;
+       }
+
+       return 0;
+}
+
+int fdt_overlay_apply(void *fdt, void *fdto)
+{
+       uint32_t delta = fdt_get_max_phandle(fdt) + 1;
+       int ret;
+
+       FDT_CHECK_HEADER(fdt);
+       FDT_CHECK_HEADER(fdto);
+
+       ret = overlay_adjust_local_phandles(fdto, delta);
+       if (ret)
+               goto err;
+
+       ret = overlay_update_local_references(fdto, delta);
+       if (ret)
+               goto err;
+
+       ret = overlay_fixup_phandles(fdt, fdto);
+       if (ret)
+               goto err;
+
+       ret = overlay_merge(fdt, fdto);
+       if (ret)
+               goto err;
+
+       /*
+        * The overlay has been damaged, erase its magic.
+        */
+       fdt_set_magic(fdto, ~0);
+
+       return 0;
+
+err:
+       /*
+        * The overlay might have been damaged, erase its magic.
+        */
+       fdt_set_magic(fdto, ~0);
+
+       /*
+        * The base device tree might have been damaged, erase its
+        * magic.
+        */
+       fdt_set_magic(fdt, ~0);
+
+       return ret;
+}