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Subject[PATCH 5/6] OF: Introduce Device Tree resolve support.
Date
Introduce support for dynamic device tree resolution.
Using it, it is possible to prepare a device tree that's
been loaded on runtime to be modified and inserted at the kernel
live tree.

Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>
---
.../devicetree/dynamic-resolution-notes.txt | 25 ++
drivers/of/Kconfig | 9 +
drivers/of/Makefile | 1 +
drivers/of/resolver.c | 394 +++++++++++++++++++++
include/linux/of.h | 17 +
5 files changed, 446 insertions(+)
create mode 100644 Documentation/devicetree/dynamic-resolution-notes.txt
create mode 100644 drivers/of/resolver.c

diff --git a/Documentation/devicetree/dynamic-resolution-notes.txt b/Documentation/devicetree/dynamic-resolution-notes.txt
new file mode 100644
index 0000000..0b396c4
--- /dev/null
+++ b/Documentation/devicetree/dynamic-resolution-notes.txt
@@ -0,0 +1,25 @@
+Device Tree Dynamic Resolver Notes
+----------------------------------
+
+This document describes the implementation of the in-kernel
+Device Tree resolver, residing in drivers/of/resolver.c and is a
+companion document to Documentation/devicetree/dt-object-internal.txt[1]
+
+How the resolver works
+----------------------
+
+The resolver is given as an input an arbitrary tree compiled with the
+proper dtc option and having a /plugin/ tag. This generates the
+appropriate __fixups__ & __local_fixups__ nodes as described in [1].
+
+In sequence the resolver works by the following steps:
+
+1. Get the maximum device tree phandle value from the live tree + 1.
+2. Adjust all the local phandles of the tree to resolve by that amount.
+3. Using the __local__fixups__ node information adjust all local references
+ by the same amount.
+4. For each property in the __fixups__ node locate the node it references
+ in the live tree. This is the label used to tag the node.
+5. Retrieve the phandle of the target of the fixup.
+5. For each fixup in the property locate the node:property:offset location
+ and replace it with the phandle value.
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index d37bfcf..f9a6193 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -83,4 +83,13 @@ config OF_MTD
depends on MTD
def_bool y

+config OF_RESOLVE
+ bool "OF Dynamic resolution support"
+ depends on OF
+ select OF_DYNAMIC
+ select OF_DEVICE
+ help
+ Enable OF dynamic resolution support. This allows you to
+ load Device Tree object fragments are run time.
+
endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index abcc08a..9a809c9 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_OF_MDIO) += of_mdio.o
obj-$(CONFIG_OF_PCI) += of_pci.o
obj-$(CONFIG_OF_PCI_IRQ) += of_pci_irq.o
obj-$(CONFIG_OF_MTD) += of_mtd.o
+obj-$(CONFIG_OF_RESOLVE) += resolver.o
diff --git a/drivers/of/resolver.c b/drivers/of/resolver.c
new file mode 100644
index 0000000..016d7da
--- /dev/null
+++ b/drivers/of/resolver.c
@@ -0,0 +1,394 @@
+/*
+ * Functions for dealing with DT resolution
+ *
+ * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
+ * Copyright (C) 2012 Texas Instruments Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_fdt.h>
+#include <linux/string.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+/**
+ * Find a subtree's maximum phandle value.
+ */
+static phandle __of_get_tree_max_phandle(struct device_node *node,
+ phandle max_phandle)
+{
+ struct device_node *child;
+
+ if (node->phandle != 0 && node->phandle != OF_PHANDLE_ILLEGAL &&
+ node->phandle > max_phandle)
+ max_phandle = node->phandle;
+
+ __for_each_child_of_node(node, child)
+ max_phandle = __of_get_tree_max_phandle(child, max_phandle);
+
+ return max_phandle;
+}
+
+/**
+ * Find live tree's maximum phandle value.
+ */
+static phandle of_get_tree_max_phandle(void)
+{
+ struct device_node *node;
+ phandle phandle;
+
+ /* get root node */
+ node = of_find_node_by_path("/");
+ if (node == NULL)
+ return OF_PHANDLE_ILLEGAL;
+
+ /* now search recursively */
+ read_lock(&devtree_lock);
+ phandle = __of_get_tree_max_phandle(node, 0);
+ read_unlock(&devtree_lock);
+
+ of_node_put(node);
+
+ return phandle;
+}
+
+/**
+ * Adjust a subtree's phandle values by a given delta.
+ * Makes sure not to just adjust the device node's phandle value,
+ * but modify the phandle properties values as well.
+ */
+static void __of_adjust_tree_phandles(struct device_node *node,
+ int phandle_delta)
+{
+ struct device_node *child;
+ struct property *prop;
+ phandle phandle;
+
+ /* first adjust the node's phandle direct value */
+ if (node->phandle != 0 && node->phandle != OF_PHANDLE_ILLEGAL)
+ node->phandle += phandle_delta;
+
+ /* now adjust phandle & linux,phandle values */
+ for_each_property_of_node(node, prop) {
+
+ /* only look for these two */
+ if (of_prop_cmp(prop->name, "phandle") != 0 &&
+ of_prop_cmp(prop->name, "linux,phandle") != 0)
+ continue;
+
+ /* must be big enough */
+ if (prop->length < 4)
+ continue;
+
+ /* read phandle value */
+ phandle = be32_to_cpu(*(uint32_t *)prop->value);
+ if (phandle == OF_PHANDLE_ILLEGAL) /* unresolved */
+ continue;
+
+ /* adjust */
+ *(uint32_t *)prop->value = cpu_to_be32(node->phandle);
+ }
+
+ /* now do the children recursively */
+ __for_each_child_of_node(node, child)
+ __of_adjust_tree_phandles(child, phandle_delta);
+}
+
+/**
+ * Adjust the local phandle references by the given phandle delta.
+ * Assumes the existances of a __local_fixups__ node at the root
+ * of the tree. Does not take any devtree locks so make sure you
+ * call this on a tree which is at the detached state.
+ */
+static int __of_adjust_tree_phandle_references(struct device_node *node,
+ int phandle_delta)
+{
+ phandle phandle;
+ struct device_node *refnode, *child;
+ struct property *rprop, *sprop;
+ char *propval, *propcur, *propend, *nodestr, *propstr, *s;
+ int offset, propcurlen;
+ int err;
+
+ /* locate the symbols & fixups nodes on resolve */
+ __for_each_child_of_node(node, child)
+ if (of_node_cmp(child->name, "__local_fixups__") == 0)
+ break;
+
+ /* no local fixups */
+ if (child == NULL)
+ return 0;
+
+ /* find the local fixups property */
+ for_each_property_of_node(child, rprop) {
+
+ /* skip properties added automatically */
+ if (of_prop_cmp(rprop->name, "name") == 0)
+ continue;
+
+ /* make a copy */
+ propval = kmalloc(rprop->length, GFP_KERNEL);
+ if (propval == NULL) {
+ pr_err("%s: Could not copy value of '%s'\n",
+ __func__, rprop->name);
+ return -ENOMEM;
+ }
+ memcpy(propval, rprop->value, rprop->length);
+
+ propend = propval + rprop->length;
+ for (propcur = propval; propcur < propend;
+ propcur += propcurlen + 1) {
+
+ propcurlen = strlen(propcur);
+
+ nodestr = propcur;
+ s = strchr(propcur, ':');
+ if (s == NULL) {
+ pr_err("%s: Illegal symbol entry '%s' (1)\n",
+ __func__, propcur);
+ err = -EINVAL;
+ goto err_fail;
+ }
+ *s++ = '\0';
+
+ propstr = s;
+ s = strchr(s, ':');
+ if (s == NULL) {
+ pr_err("%s: Illegal symbol entry '%s' (2)\n",
+ __func__, (char *)rprop->value);
+ err = -EINVAL;
+ goto err_fail;
+ }
+
+ *s++ = '\0';
+ offset = simple_strtoul(s, NULL, 10);
+
+ /* look into the resolve node for the full path */
+ refnode = __of_find_node_by_full_name(node, nodestr);
+ if (refnode == NULL) {
+ pr_warn("%s: Could not find refnode '%s'\n",
+ __func__, (char *)rprop->value);
+ continue;
+ }
+
+ /* now find the property */
+ for_each_property_of_node(refnode, sprop) {
+ if (of_prop_cmp(sprop->name, propstr) == 0)
+ break;
+ }
+
+ if (sprop == NULL) {
+ pr_err("%s: Could not find property '%s'\n",
+ __func__, (char *)rprop->value);
+ err = -ENOENT;
+ goto err_fail;
+ }
+
+ phandle = be32_to_cpu(*(uint32_t *)
+ (sprop->value + offset));
+ *(uint32_t *)(sprop->value + offset) =
+ cpu_to_be32(phandle + phandle_delta);
+ }
+
+ kfree(propval);
+ }
+
+ return 0;
+
+err_fail:
+ kfree(propval);
+ return err;
+}
+
+/**
+ * of_resolve - Resolve the given node against the live tree.
+ *
+ * @resolve: Node to resolve
+ *
+ * Perform dynamic Device Tree resolution against the live tree
+ * to the given node to resolve. This depends on the live tree
+ * having a __symbols__ node, and the resolve node the __fixups__ &
+ * __local_fixups__ nodes (if needed).
+ * The result of the operation is a resolve node that it's contents
+ * are fit to be inserted or operate upon the live tree.
+ * Returns 0 on success or a negative error value on error.
+ */
+int of_resolve(struct device_node *resolve)
+{
+ struct device_node *child, *refnode;
+ struct device_node *root_sym, *resolve_sym, *resolve_fix;
+ struct property *rprop, *sprop;
+ const char *refpath;
+ char *propval, *propcur, *propend, *nodestr, *propstr, *s;
+ int offset, propcurlen;
+ phandle phandle, phandle_delta;
+ int err;
+
+ /* the resolve node must exist, and be detached */
+ if (resolve == NULL ||
+ !of_node_check_flag(resolve, OF_DETACHED)) {
+ return -EINVAL;
+ }
+
+ /* first we need to adjust the phandles */
+ phandle_delta = of_get_tree_max_phandle() + 1;
+ __of_adjust_tree_phandles(resolve, phandle_delta);
+ err = __of_adjust_tree_phandle_references(resolve, phandle_delta);
+ if (err != 0)
+ return err;
+
+ root_sym = NULL;
+ resolve_sym = NULL;
+ resolve_fix = NULL;
+
+ /* this may fail (if no fixups are required) */
+ root_sym = of_find_node_by_path("/__symbols__");
+
+ /* locate the symbols & fixups nodes on resolve */
+ __for_each_child_of_node(resolve, child) {
+
+ if (resolve_sym == NULL &&
+ of_node_cmp(child->name, "__symbols__") == 0)
+ resolve_sym = child;
+
+ if (resolve_fix == NULL &&
+ of_node_cmp(child->name, "__fixups__") == 0)
+ resolve_fix = child;
+
+ /* both found, don't bother anymore */
+ if (resolve_sym != NULL && resolve_fix != NULL)
+ break;
+ }
+
+ /* we do allow for the case where no fixups are needed */
+ if (resolve_fix == NULL)
+ goto merge_sym;
+
+ /* we need to fixup, but no root symbols... */
+ if (root_sym == NULL)
+ return -EINVAL;
+
+ for_each_property_of_node(resolve_fix, rprop) {
+
+ /* skip properties added automatically */
+ if (of_prop_cmp(rprop->name, "name") == 0)
+ continue;
+
+ err = of_property_read_string(root_sym,
+ rprop->name, &refpath);
+ if (err != 0) {
+ pr_err("%s: Could not find symbol '%s'\n",
+ __func__, rprop->name);
+ goto err_fail;
+ }
+
+ refnode = of_find_node_by_path(refpath);
+ if (refnode == NULL) {
+ pr_err("%s: Could not find node by path '%s'\n",
+ __func__, refpath);
+ err = -ENOENT;
+ goto err_fail;
+ }
+
+ phandle = refnode->phandle;
+ of_node_put(refnode);
+
+ pr_debug("%s: %s phandle is 0x%08x\n",
+ __func__, rprop->name, phandle);
+
+ /* make a copy */
+ propval = kmalloc(rprop->length, GFP_KERNEL);
+ if (propval == NULL) {
+ pr_err("%s: Could not copy value of '%s'\n",
+ __func__, rprop->name);
+ err = -ENOMEM;
+ goto err_fail;
+ }
+
+ memcpy(propval, rprop->value, rprop->length);
+
+ propend = propval + rprop->length;
+ for (propcur = propval; propcur < propend;
+ propcur += propcurlen + 1) {
+ propcurlen = strlen(propcur);
+
+ nodestr = propcur;
+ s = strchr(propcur, ':');
+ if (s == NULL) {
+ pr_err("%s: Illegal symbol "
+ "entry '%s' (1)\n",
+ __func__, (char *)rprop->value);
+ kfree(propval);
+ err = -EINVAL;
+ goto err_fail;
+ }
+ *s++ = '\0';
+
+ propstr = s;
+ s = strchr(s, ':');
+ if (s == NULL) {
+ pr_err("%s: Illegal symbol "
+ "entry '%s' (2)\n",
+ __func__, (char *)rprop->value);
+ kfree(propval);
+ err = -EINVAL;
+ goto err_fail;
+ }
+
+ *s++ = '\0';
+ offset = simple_strtoul(s, NULL, 10);
+
+ /* look into the resolve node for the full path */
+ refnode = __of_find_node_by_full_name(resolve,
+ nodestr);
+ if (refnode == NULL) {
+ pr_err("%s: Could not find refnode '%s'\n",
+ __func__, (char *)rprop->value);
+ kfree(propval);
+ err = -ENOENT;
+ goto err_fail;
+ }
+
+ /* now find the property */
+ for_each_property_of_node(refnode, sprop) {
+ if (of_prop_cmp(sprop->name, propstr) == 0)
+ break;
+ }
+
+ if (sprop == NULL) {
+ pr_err("%s: Could not find property '%s'\n",
+ __func__, (char *)rprop->value);
+ kfree(propval);
+ err = -ENOENT;
+ goto err_fail;
+ }
+
+ *(uint32_t *)(sprop->value + offset) =
+ cpu_to_be32(phandle);
+ }
+
+ kfree(propval);
+ }
+
+merge_sym:
+
+ of_node_put(root_sym);
+
+ return 0;
+
+err_fail:
+
+ if (root_sym != NULL)
+ of_node_put(root_sym);
+
+ return err;
+}
diff --git a/include/linux/of.h b/include/linux/of.h
index c38e41a..ab52243 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -650,4 +650,21 @@ static inline int of_multi_prop_cmp(const struct property *prop, const char *val

#endif /* !CONFIG_OF */

+
+/* illegal phandle value (set when unresolved) */
+#define OF_PHANDLE_ILLEGAL 0xdeadbeef
+
+#ifdef CONFIG_OF_RESOLVE
+
+int of_resolve(struct device_node *resolve);
+
+#else
+
+static inline int of_resolve(struct device_node *resolve)
+{
+ return -ENOTSUPP;
+}
+
+#endif
+
#endif /* _LINUX_OF_H */
--
1.7.12


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