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Subject[PATCH 6/6] OF: Introduce DT overlay support.
Date
Introduce DT overlay support.
Using this functionality it is possible to dynamically overlay a part of
the kernel's tree with another tree that's been dynamically loaded.
It is also possible to remove node and properties.

Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>
---
Documentation/devicetree/overlay-notes.txt | 179 +++++++
drivers/of/Kconfig | 10 +
drivers/of/Makefile | 1 +
drivers/of/overlay.c | 831 +++++++++++++++++++++++++++++
include/linux/of.h | 107 ++++
5 files changed, 1128 insertions(+)
create mode 100644 Documentation/devicetree/overlay-notes.txt
create mode 100644 drivers/of/overlay.c

diff --git a/Documentation/devicetree/overlay-notes.txt b/Documentation/devicetree/overlay-notes.txt
new file mode 100644
index 0000000..5289cbb
--- /dev/null
+++ b/Documentation/devicetree/overlay-notes.txt
@@ -0,0 +1,179 @@
+Device Tree Overlay Notes
+-------------------------
+
+This document describes the implementation of the in-kernel
+device tree overlay functionality residing in drivers/of/overlay.c and is a
+companion document to Documentation/devicetree/dt-object-internal.txt[1] &
+Documentation/devicetree/dynamic-resolution-notes.txt[2]
+
+How overlays work
+-----------------
+
+A Device Tree's overlay purpose is to modify the kernel's live tree, and
+have the modification affecting the state of the the kernel in a way that
+is reflecting the changes.
+Since the kernel mainly deals with devices, any new device node that result
+in an active device should have it created while if the device node is either
+disabled or removed all together, the affected device should be deregistered.
+
+Lets take an example where we have a foo board with the following base tree
+which is taken from [1].
+
+---- foo.dts -----------------------------------------------------------------
+ /* FOO platform */
+ / {
+ compatible = "corp,foo";
+
+ /* shared resources */
+ res: res {
+ };
+
+ /* On chip peripherals */
+ ocp: ocp {
+ /* peripherals that are always instantiated */
+ peripheral1 { ... };
+ }
+ };
+---- foo.dts -----------------------------------------------------------------
+
+The overlay bar.dts, when loaded (and resolved as described in [2]) should
+
+---- bar.dts -----------------------------------------------------------------
+/plugin/; /* allow undefined label references and record them */
+/ {
+ .... /* various properties for loader use; i.e. part id etc. */
+ fragment@0 {
+ target = <&ocp>;
+ __overlay__ {
+ /* bar peripheral */
+ bar {
+ compatible = "corp,bar";
+ ... /* various properties and child nodes */
+ }
+ };
+ };
+};
+---- bar.dts -----------------------------------------------------------------
+
+result in foo+bar.dts
+
+---- foo+bar.dts -------------------------------------------------------------
+ /* FOO platform + bar peripheral */
+ / {
+ compatible = "corp,foo";
+
+ /* shared resources */
+ res: res {
+ };
+
+ /* On chip peripherals */
+ ocp: ocp {
+ /* peripherals that are always instantiated */
+ peripheral1 { ... };
+
+ /* bar peripheral */
+ bar {
+ compatible = "corp,bar";
+ ... /* various properties and child nodes */
+ }
+ }
+ };
+---- foo+bar.dts -------------------------------------------------------------
+
+As a result of the the overlay, a new device node (bar) has been created
+so a bar platform device will be registered and if a matching device driver
+is loaded the device will be created as expected.
+
+Overlay in-kernel API
+---------------------
+
+The steps typically required to get an overlay to work are as follows:
+
+1. Use of_build_overlay_info() to create an array of initialized and
+ready to use of_overlay_info structures.
+2. Call of_overlay() to apply the overlays declared in the array.
+3. If the overlay needs to be removed, call of_overlay_revert().
+4. Finally release the memory taken by the overlay info array by
+of_free_overlay_info().
+
+/**
+ * of_build_overlay_info - Build an overlay info array
+ * @tree: Device node containing all the overlays
+ * @cntp: Pointer to where the overlay info count will be help
+ * @ovinfop: Pointer to the pointer of an overlay info structure.
+ *
+ * Helper function that given a tree containing overlay information,
+ * allocates and builds an overlay info array containing it, ready
+ * for use using of_overlay.
+ *
+ * Returns 0 on success with the @cntp @ovinfop pointers valid,
+ * while on error a negative error value is returned.
+ */
+int of_build_overlay_info(struct device_node *tree,
+ int *cntp, struct of_overlay_info **ovinfop);
+
+/**
+ * of_free_overlay_info - Free an overlay info array
+ * @count: Number of of_overlay_info's
+ * @ovinfo_tab: Array of overlay_info's to free
+ *
+ * Releases the memory of a previously allocate ovinfo array
+ * by of_build_overlay_info.
+ * Returns 0, or an error if the arguments are bogus.
+ */
+int of_free_overlay_info(int count, struct of_overlay_info *ovinfo_tab);
+
+/**
+ * of_overlay - Apply @count overlays pointed at by @ovinfo_tab
+ * @count: Number of of_overlay_info's
+ * @ovinfo_tab: Array of overlay_info's to apply
+ *
+ * Applies the overlays given, while handling all error conditions
+ * appropriately. Either the operation succeeds, or if it fails the
+ * live tree is reverted to the state before the attempt.
+ * Returns 0, or an error if the overlay attempt failed.
+ */
+int of_overlay(int count, struct of_overlay_info *ovinfo_tab);
+
+/**
+ * of_overlay_revert - Revert a previously applied overlay
+ * @count: Number of of_overlay_info's
+ * @ovinfo_tab: Array of overlay_info's to apply
+ *
+ * Revert a previous overlay. The state of the live tree
+ * is reverted to the one before the overlay.
+ * Returns 0, or an error if the overlay table is not given.
+ */
+int of_overlay_revert(int count, struct of_overlay_info *ovinfo_tab);
+
+Overlay DTS Format
+------------------
+
+The DTS of an overlay should have the following format:
+
+{
+ /* ignored properties by the overlay */
+
+ fragment@0 { /* first child node */
+ target=<phandle>; /* target of the overlay */
+ __overlay__ {
+ property-a; /* add property-a to the target */
+ -property-b; /* remove property-b from target */
+ node-a { /* add to an existing, or create a node-a */
+ ...
+ };
+ -node-b { /* remove an existing node-b */
+ ...
+ };
+ };
+ }
+ fragment@1 { /* second child node */
+ ...
+ };
+ /* more fragments follow */
+}
+
+It should be noted that the DT overlay format described is the one expected
+by the of_build_overlay_info() function, which is a helper function. There
+is nothing stopping someone coming up with his own DTS format and that will
+end up filling in the fields of the of_overlay_info array.
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index f9a6193..964a1c2 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -92,4 +92,14 @@ config OF_RESOLVE
Enable OF dynamic resolution support. This allows you to
load Device Tree object fragments are run time.

+config OF_OVERLAY
+ bool "OF overlay support"
+ depends on OF
+ select OF_DYNAMIC
+ select OF_DEVICE
+ select OF_RESOLVE
+ help
+ OpenFirmware overlay support. Allows you to modify on runtime the
+ live tree using overlays.
+
endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index 9a809c9..bc06912 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -12,3 +12,4 @@ 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
+obj-$(CONFIG_OF_OVERLAY) += overlay.o
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
new file mode 100644
index 0000000..f65c3a3
--- /dev/null
+++ b/drivers/of/overlay.c
@@ -0,0 +1,831 @@
+/*
+ * Functions for working with device tree overlays
+ *
+ * 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/string.h>
+#include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+
+/**
+ * Apply a single overlay node recursively.
+ *
+ * Property or node names that start with '-' signal that
+ * the property/node is to be removed.
+ *
+ * All the property notifiers are appropriately called.
+ * Note that the in case of an error the target node is left
+ * in a inconsistent state. Error recovery should be performed
+ * by recording the modification using the of notifiers.
+ */
+static int of_overlay_apply_one(struct device_node *target,
+ const struct device_node *overlay)
+{
+ const char *pname, *cname;
+ struct device_node *child, *tchild;
+ struct property *prop, *propn, *tprop;
+ int remove;
+ char *full_name;
+ const char *suffix;
+ int ret;
+
+ /* sanity checks */
+ if (target == NULL || overlay == NULL)
+ return -EINVAL;
+
+ for_each_property_of_node(overlay, prop) {
+
+ /* don't touch, 'name' */
+ if (of_prop_cmp(prop->name, "name") == 0)
+ continue;
+
+ /* default is add */
+ remove = 0;
+ pname = prop->name;
+ if (*pname == '-') { /* skip, - notes removal */
+ pname++;
+ remove = 1;
+ propn = NULL;
+ } else {
+ propn = __of_copy_property(prop,
+ GFP_KERNEL);
+ if (propn == NULL)
+ return -ENOMEM;
+ }
+
+ tprop = of_find_property(target, pname, NULL);
+
+ /* found? */
+ if (tprop != NULL) {
+ if (propn != NULL)
+ ret = of_update_property(target, propn);
+ else
+ ret = of_remove_property(target, tprop);
+ } else {
+ if (propn != NULL)
+ ret = of_add_property(target, propn);
+ else
+ ret = 0;
+ }
+ if (ret != 0)
+ return ret;
+ }
+
+ __for_each_child_of_node(overlay, child) {
+
+ /* default is add */
+ remove = 0;
+ cname = child->name;
+ if (*cname == '-') { /* skip, - notes removal */
+ cname++;
+ remove = 1;
+ }
+
+ /* special case for nodes with a suffix */
+ suffix = strrchr(child->full_name, '@');
+ if (suffix != NULL) {
+ cname = kbasename(child->full_name);
+ WARN_ON(cname == NULL); /* sanity check */
+ if (cname == NULL)
+ continue;
+ if (*cname == '-')
+ cname++;
+ }
+
+ tchild = of_get_child_by_name(target, cname);
+ if (tchild != NULL) {
+
+ if (!remove) {
+
+ /* apply overlay recursively */
+ ret = of_overlay_apply_one(tchild, child);
+ of_node_put(tchild);
+
+ if (ret != 0)
+ return ret;
+
+ } else {
+
+ ret = of_detach_node(tchild);
+ of_node_put(tchild);
+ }
+
+ } else {
+
+ if (!remove) {
+ full_name = kasprintf(GFP_KERNEL, "%s/%s",
+ target->full_name, cname);
+ if (full_name == NULL)
+ return -ENOMEM;
+
+ /* create empty tree as a target */
+ tchild = __of_create_empty_node(cname,
+ child->type, full_name,
+ child->phandle, GFP_KERNEL);
+
+ /* free either way */
+ kfree(full_name);
+
+ if (tchild == NULL)
+ return -ENOMEM;
+
+ /* point to parent */
+ tchild->parent = target;
+
+ ret = of_attach_node(tchild);
+ if (ret != 0)
+ return ret;
+
+ /* apply the overlay */
+ ret = of_overlay_apply_one(tchild, child);
+ if (ret != 0) {
+ __of_free_tree(tchild);
+ return ret;
+ }
+ }
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * Lookup an overlay device entry
+ */
+struct of_overlay_device_entry *of_overlay_device_entry_lookup(
+ struct of_overlay_info *ovinfo, struct device_node *node)
+{
+ struct of_overlay_device_entry *re;
+
+ /* no need for locks, we're under the ovinfo->lock */
+ list_for_each_entry(re, &ovinfo->de_list, node) {
+ if (re->np == node)
+ return re;
+ }
+ return NULL;
+}
+
+/**
+ * Add an overlay log entry
+ */
+static int of_overlay_log_entry_entry_add(struct of_overlay_info *ovinfo,
+ unsigned long action, struct device_node *dn,
+ struct property *prop)
+{
+ struct of_overlay_log_entry *le;
+
+ /* check */
+ if (ovinfo == NULL || dn == NULL)
+ return -EINVAL;
+
+ le = kzalloc(sizeof(*le), GFP_KERNEL);
+ if (le == NULL) {
+ pr_err("%s: Failed to allocate\n", __func__);
+ return -ENOMEM;
+ }
+
+ /* get a reference to the node */
+ le->action = action;
+ le->np = of_node_get(dn);
+ le->prop = prop;
+
+ if (action == OF_RECONFIG_UPDATE_PROPERTY && prop)
+ le->old_prop = of_find_property(dn, prop->name, NULL);
+
+ list_add_tail(&le->node, &ovinfo->le_list);
+
+ return 0;
+}
+
+/**
+ * Add an overlay device entry
+ */
+static void of_overlay_device_entry_entry_add(struct of_overlay_info *ovinfo,
+ struct device_node *node, struct platform_device *pdev,
+ int state)
+{
+ struct of_overlay_device_entry *re;
+ int fresh;
+
+ /* check */
+ if (ovinfo == NULL)
+ return;
+
+ fresh = 0;
+ re = of_overlay_device_entry_lookup(ovinfo, node);
+ if (re == NULL) {
+ re = kzalloc(sizeof(*re), GFP_KERNEL);
+ if (re == NULL) {
+ pr_err("%s: Failed to allocate\n", __func__);
+ return;
+ }
+ fresh = 1;
+ }
+
+ if (re->np == NULL)
+ re->np = of_node_get(node);
+ if (re->pdev == NULL)
+ re->pdev = of_dev_get(pdev);
+ re->state = state;
+
+ if (fresh)
+ list_add_tail(&re->node, &ovinfo->de_list);
+}
+
+/**
+ * Overlay OF notifier
+ *
+ * Called every time there's a property/node modification
+ * Every modification causes a log entry addition, while
+ * any modification that causes a node's state to change
+ * from/to disabled to/from enabled causes a device entry
+ * addition.
+ */
+static int of_overlay_notify(struct notifier_block *nb,
+ unsigned long action, void *arg)
+{
+#ifdef DEBUG
+ char *propstr = NULL, *spropstr = NULL;
+#endif
+ struct of_overlay_info *ovinfo;
+ struct device_node *node;
+ struct property *prop, *sprop, *cprop;
+ struct of_prop_reconfig *pr;
+ struct platform_device *pdev;
+ int state;
+ int err = 0;
+
+ ovinfo = container_of(nb, struct of_overlay_info, notifier);
+
+ /* prep vars */
+ switch (action) {
+ case OF_RECONFIG_ATTACH_NODE:
+ case OF_RECONFIG_DETACH_NODE:
+ node = arg;
+ if (node == NULL)
+ return notifier_from_errno(-EINVAL);
+ prop = NULL;
+#ifdef DEBUG
+ propstr = NULL;
+#endif
+ break;
+ case OF_RECONFIG_ADD_PROPERTY:
+ case OF_RECONFIG_REMOVE_PROPERTY:
+ case OF_RECONFIG_UPDATE_PROPERTY:
+ pr = arg;
+ if (pr == NULL)
+ return notifier_from_errno(-EINVAL);
+ node = pr->dn;
+ if (node == NULL)
+ return notifier_from_errno(-EINVAL);
+ prop = pr->prop;
+ if (prop == NULL)
+ return notifier_from_errno(-EINVAL);
+#ifdef DEBUG
+ propstr = __of_dump_prop(prop);
+#endif
+ break;
+ default:
+ return notifier_from_errno(0);
+ }
+
+ /* add to the log */
+ err = of_overlay_log_entry_entry_add(ovinfo, action, node, prop);
+ if (err != 0)
+ return notifier_from_errno(err);
+
+#ifdef DEBUG
+ switch (action) {
+ case OF_RECONFIG_ATTACH_NODE:
+ pr_debug("ATTACH_NODE: %s\n", node->full_name);
+ break;
+ case OF_RECONFIG_DETACH_NODE:
+ pr_debug("DETACH_NODE: %s\n", node->full_name);
+ break;
+ case OF_RECONFIG_ADD_PROPERTY:
+ pr_debug("ADD_PROP: %s %s%s\n", node->full_name,
+ prop->name, propstr);
+ break;
+ case OF_RECONFIG_REMOVE_PROPERTY:
+ pr_debug("REMOVE_PROP: %s %s%s\n", node->full_name,
+ prop->name, propstr);
+ break;
+ case OF_RECONFIG_UPDATE_PROPERTY:
+ sprop = of_find_property(node, prop->name, NULL);
+ if (sprop)
+ spropstr = __of_dump_prop(sprop);
+ pr_debug("UPDATE_PROP: %s '%s%s' -> '%s%s'\n", node->full_name,
+ prop->name, spropstr,
+ prop->name, propstr);
+ break;
+
+ }
+
+ /* NULL is fine */
+ kfree(propstr);
+ kfree(spropstr);
+#endif
+
+ /* come up with the device entry (if any) */
+ pdev = NULL;
+ state = 0;
+
+ /* determine the state the node will end up */
+ switch (action) {
+ case OF_RECONFIG_ATTACH_NODE:
+ /* we demand that a compatible node is present */
+ state = of_find_property(node, "compatible", NULL) &&
+ of_device_is_available(node);
+ break;
+ case OF_RECONFIG_DETACH_NODE:
+ state = 0;
+ pdev = of_find_device_by_node(node);
+ break;
+ case OF_RECONFIG_ADD_PROPERTY:
+ case OF_RECONFIG_REMOVE_PROPERTY:
+ case OF_RECONFIG_UPDATE_PROPERTY:
+ /* either one cause a change in state */
+ if (strcmp(prop->name, "status") != 0 &&
+ strcmp(prop->name, "compatible") != 0)
+ return notifier_from_errno(0);
+
+ if (strcmp(prop->name, "status") == 0) {
+ /* status */
+ cprop = of_find_property(node, "compatible", NULL);
+ sprop = action != OF_RECONFIG_REMOVE_PROPERTY ?
+ prop : NULL;
+ } else {
+ /* compatible */
+ sprop = of_find_property(node, "status", NULL);
+ cprop = action != OF_RECONFIG_REMOVE_PROPERTY ?
+ prop : NULL;
+ }
+
+ state = cprop && cprop->length > 0 &&
+ (!sprop || (sprop->length > 0 &&
+ (strcmp(sprop->value, "okay") == 0 ||
+ strcmp(sprop->value, "ok") == 0)));
+ break;
+
+ default:
+ return notifier_from_errno(0);
+ }
+
+ if (state == 0)
+ pdev = of_find_device_by_node(node);
+
+ of_overlay_device_entry_entry_add(ovinfo, node, pdev, state);
+
+ return notifier_from_errno(err);
+}
+
+/**
+ * Prepare for the overlay, for now it just registers the
+ * notifier.
+ */
+static int of_overlay_prep_one(struct of_overlay_info *ovinfo)
+{
+ int err;
+
+ err = of_reconfig_notifier_register(&ovinfo->notifier);
+ if (err != 0) {
+ pr_err("%s: failed to register notifier for '%s'\n",
+ __func__, ovinfo->target->full_name);
+ return err;
+ }
+ return 0;
+}
+
+/**
+ * Revert one overlay
+ * Either due to an error, or due to normal overlay removal.
+ * Using the log entries, we revert any change to the live tree.
+ * In the same manner, using the device entries we enable/disable
+ * the platform devices appropriately.
+ */
+static void of_overlay_revert_one(struct of_overlay_info *ovinfo)
+{
+ struct of_overlay_device_entry *re, *ren;
+ struct of_overlay_log_entry *le, *len;
+ struct property *prop, **propp;
+ struct platform_device *pdev, *parent_pdev;
+ int ret;
+ unsigned long flags;
+
+ if (!ovinfo || !ovinfo->target || !ovinfo->overlay)
+ return;
+
+ pr_debug("%s: Reverting overlay on '%s'\n", __func__,
+ ovinfo->target->full_name);
+
+ /* overlay applied correctly, now create/destroy pdevs */
+ list_for_each_entry_safe_reverse(re, ren, &ovinfo->de_list, node) {
+
+ if (!re->state) {
+
+ parent_pdev = of_find_device_by_node(re->np->parent);
+
+ pr_debug("%s: creating new platform device "
+ "new_node='%s' %p\n",
+ __func__, re->np->full_name, re->np);
+
+ pdev = of_platform_device_create(re->np, NULL,
+ parent_pdev ? &parent_pdev->dev : NULL);
+ of_dev_put(parent_pdev);
+
+ if (pdev == NULL) {
+ pr_warn("%s: Failed to create platform device "
+ "for '%s'\n",
+ __func__, re->np->full_name);
+ }
+
+ } else {
+
+ if (re->pdev) {
+ pr_debug("%s: removing pdev %s\n", __func__,
+ dev_name(&re->pdev->dev));
+ platform_device_unregister(re->pdev);
+ }
+ }
+
+ of_node_put(re->np);
+
+ list_del(&re->node);
+
+ kfree(re);
+ }
+
+ list_for_each_entry_safe_reverse(le, len, &ovinfo->le_list, node) {
+
+ ret = 0;
+ switch (le->action) {
+ case OF_RECONFIG_ATTACH_NODE:
+ pr_debug("Reverting ATTACH_NODE %s\n",
+ le->np->full_name);
+ ret = of_detach_node(le->np);
+ break;
+
+ case OF_RECONFIG_DETACH_NODE:
+ pr_debug("Reverting DETACH_NODE %s\n",
+ le->np->full_name);
+ ret = of_attach_node(le->np);
+ break;
+
+ case OF_RECONFIG_ADD_PROPERTY:
+ pr_debug("Reverting ADD_PROPERTY %s %s\n",
+ le->np->full_name, le->prop->name);
+ ret = of_remove_property(le->np, le->prop);
+ break;
+
+ case OF_RECONFIG_REMOVE_PROPERTY:
+ case OF_RECONFIG_UPDATE_PROPERTY:
+
+ pr_debug("Reverting %s_PROPERTY %s %s\n",
+ le->action == OF_RECONFIG_REMOVE_PROPERTY ?
+ "REMOVE" : "UPDATE",
+ le->np->full_name, le->prop->name);
+
+ /* property is possibly on deadprops (avoid alloc) */
+ write_lock_irqsave(&devtree_lock, flags);
+ prop = le->action == OF_RECONFIG_REMOVE_PROPERTY ?
+ le->prop : le->old_prop;
+ propp = &le->np->deadprops;
+ while (*propp != NULL) {
+ if (*propp == prop)
+ break;
+ propp = &(*propp)->next;
+ }
+ if (*propp != NULL) {
+ /* remove it from deadprops */
+ (*propp)->next = prop->next;
+ write_unlock_irqrestore(&devtree_lock, flags);
+ } else {
+ write_unlock_irqrestore(&devtree_lock, flags);
+ /* not found, just make a copy */
+ prop = __of_copy_property(prop, GFP_KERNEL);
+ if (prop == NULL) {
+ pr_err("%s: Failed to copy property\n",
+ __func__);
+ break;
+ }
+ }
+
+ if (le->action == OF_RECONFIG_REMOVE_PROPERTY)
+ ret = of_add_property(le->np, prop);
+ else
+ ret = of_update_property(le->np, prop);
+ break;
+
+ default:
+ /* nothing */
+ break;
+ }
+
+ if (ret != 0)
+ pr_err("%s: revert on node %s Failed!\n",
+ __func__, le->np->full_name);
+
+ of_node_put(le->np);
+
+ list_del(&le->node);
+
+ kfree(le);
+ }
+}
+
+/**
+ * Perform the post overlay work.
+ *
+ * We unregister the notifier, and in the case on an error we
+ * revert the overlay.
+ * If the overlay applied correctly, we iterare over the device entries
+ * and create/destroy the platform devices appropriately.
+ */
+static int of_overlay_post_one(struct of_overlay_info *ovinfo, int err)
+{
+ struct of_overlay_device_entry *re, *ren;
+ struct platform_device *pdev, *parent_pdev;
+
+ of_reconfig_notifier_unregister(&ovinfo->notifier);
+
+ if (err != 0) {
+ /* revert this (possible partially applied) overlay */
+ of_overlay_revert_one(ovinfo);
+ return 0;
+ }
+
+ /* overlay applied correctly, now create/destroy pdevs */
+ list_for_each_entry_safe(re, ren, &ovinfo->de_list, node) {
+
+ if (re->state) {
+
+ parent_pdev = of_find_device_by_node(re->np->parent);
+
+ pr_debug("%s: creating new platform device "
+ "new_node='%s' %p\n",
+ __func__, re->np->full_name, re->np);
+
+ pdev = of_platform_device_create(re->np, NULL,
+ parent_pdev ? &parent_pdev->dev : NULL);
+ of_dev_put(parent_pdev);
+
+ if (pdev == NULL) {
+ pr_warn("%s: Failed to create platform device "
+ "for '%s'\n",
+ __func__, re->np->full_name);
+ }
+
+ /* keep it around */
+ re->pdev = pdev;
+
+ } else {
+
+ if (re->pdev) {
+ platform_device_unregister(re->pdev);
+ }
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * of_overlay - Apply @count overlays pointed at by @ovinfo_tab
+ * @count: Number of of_overlay_info's
+ * @ovinfo_tab: Array of overlay_info's to apply
+ *
+ * Applies the overlays given, while handling all error conditions
+ * appropriately. Either the operation succeeds, or if it fails the
+ * live tree is reverted to the state before the attempt.
+ * Returns 0, or an error if the overlay attempt failed.
+ */
+int of_overlay(int count, struct of_overlay_info *ovinfo_tab)
+{
+ struct of_overlay_info *ovinfo;
+ int i, err;
+
+ if (!ovinfo_tab)
+ return -EINVAL;
+
+ /* first we apply the overlays atomically */
+ for (i = 0; i < count; i++) {
+
+ ovinfo = &ovinfo_tab[i];
+
+ mutex_lock(&ovinfo->lock);
+
+ err = of_overlay_prep_one(ovinfo);
+ if (err == 0)
+ err = of_overlay_apply_one(ovinfo->target,
+ ovinfo->overlay);
+ of_overlay_post_one(ovinfo, err);
+
+ mutex_unlock(&ovinfo->lock);
+
+ if (err != 0) {
+ pr_err("%s: overlay failed '%s'\n",
+ __func__, ovinfo->target->full_name);
+ goto err_fail;
+ }
+ }
+
+ return 0;
+
+err_fail:
+ while (--i >= 0) {
+ ovinfo = &ovinfo_tab[i];
+
+ mutex_lock(&ovinfo->lock);
+ of_overlay_revert_one(ovinfo);
+ mutex_unlock(&ovinfo->lock);
+ }
+
+ return err;
+}
+
+/**
+ * of_overlay_revert - Revert a previously applied overlay
+ * @count: Number of of_overlay_info's
+ * @ovinfo_tab: Array of overlay_info's to apply
+ *
+ * Revert a previous overlay. The state of the live tree
+ * is reverted to the one before the overlay.
+ * Returns 0, or an error if the overlay table is not given.
+ */
+int of_overlay_revert(int count, struct of_overlay_info *ovinfo_tab)
+{
+ struct of_overlay_info *ovinfo;
+ int i;
+
+ if (!ovinfo_tab)
+ return -EINVAL;
+
+ /* revert the overlays in reverse */
+ for (i = count - 1; i >= 0; i--) {
+
+ ovinfo = &ovinfo_tab[i];
+
+ mutex_lock(&ovinfo->lock);
+ of_overlay_revert_one(ovinfo);
+ mutex_unlock(&ovinfo->lock);
+
+ }
+
+ return 0;
+}
+
+/**
+ * of_init_overlay_info - Initialize a single of_overlay_info structure
+ * @ovinfo: Pointer to the overlay info structure to initialize
+ *
+ * Initialize a single overlay info structure.
+ */
+void of_init_overlay_info(struct of_overlay_info *ovinfo)
+{
+ memset(ovinfo, 0, sizeof(ovinfo));
+ mutex_init(&ovinfo->lock);
+ INIT_LIST_HEAD(&ovinfo->de_list);
+ INIT_LIST_HEAD(&ovinfo->le_list);
+
+ ovinfo->notifier.notifier_call = of_overlay_notify;
+}
+
+/**
+ * of_fill_overlay_info - Fill an overlay info structure
+ * @info_node: Device node containing the overlay
+ * @ovinfo: Pointer to the overlay info structure to fill
+ *
+ * Fills an overlay info structure with the overlay information
+ * from a device node. This device node must have a target property
+ * which contains a phandle of the overlay target node, and an
+ * __overlay__ child node which has the overlay contents.
+ * Both ovinfo->target & ovinfo->overlay have their references taken.
+ *
+ * Returns 0 on success, or a negative error value.
+ */
+int of_fill_overlay_info(struct device_node *info_node,
+ struct of_overlay_info *ovinfo)
+{
+ u32 val;
+ int ret;
+
+ if (!info_node || !ovinfo)
+ return -EINVAL;
+
+ ret = of_property_read_u32(info_node, "target", &val);
+ if (ret != 0)
+ goto err_fail;
+
+ ovinfo->target = of_find_node_by_phandle(val);
+ if (ovinfo->target == NULL)
+ goto err_fail;
+
+ ovinfo->overlay = of_get_child_by_name(info_node, "__overlay__");
+ if (ovinfo->overlay == NULL)
+ goto err_fail;
+
+ return 0;
+
+err_fail:
+ of_node_put(ovinfo->target);
+ of_node_put(ovinfo->overlay);
+
+ memset(ovinfo, 0, sizeof(*ovinfo));
+ return -EINVAL;
+}
+
+/**
+ * of_build_overlay_info - Build an overlay info array
+ * @tree: Device node containing all the overlays
+ * @cntp: Pointer to where the overlay info count will be help
+ * @ovinfop: Pointer to the pointer of an overlay info structure.
+ *
+ * Helper function that given a tree containing overlay information,
+ * allocates and builds an overlay info array containing it, ready
+ * for use using of_overlay.
+ *
+ * Returns 0 on success with the @cntp @ovinfop pointers valid,
+ * while on error a negative error value is returned.
+ */
+int of_build_overlay_info(struct device_node *tree,
+ int *cntp, struct of_overlay_info **ovinfop)
+{
+ struct device_node *node;
+ struct of_overlay_info *ovinfo;
+ int cnt, err;
+
+ if (tree == NULL || cntp == NULL || ovinfop == NULL)
+ return -EINVAL;
+
+ /* worst case; every child is a node */
+ cnt = 0;
+ for_each_child_of_node(tree, node)
+ cnt++;
+
+ ovinfo = kzalloc(cnt * sizeof(*ovinfo), GFP_KERNEL);
+ if (ovinfo == NULL)
+ return -ENOMEM;
+
+ cnt = 0;
+ for_each_child_of_node(tree, node) {
+
+ of_init_overlay_info(&ovinfo[cnt]);
+ err = of_fill_overlay_info(node, &ovinfo[cnt]);
+ if (err == 0)
+ cnt++;
+ }
+
+ /* if nothing filled, return error */
+ if (cnt == 0) {
+ kfree(ovinfo);
+ return -ENODEV;
+ }
+
+ *cntp = cnt;
+ *ovinfop = ovinfo;
+
+ return 0;
+}
+
+/**
+ * of_free_overlay_info - Free an overlay info array
+ * @count: Number of of_overlay_info's
+ * @ovinfo_tab: Array of overlay_info's to free
+ *
+ * Releases the memory of a previously allocate ovinfo array
+ * by of_build_overlay_info.
+ * Returns 0, or an error if the arguments are bogus.
+ */
+int of_free_overlay_info(int count, struct of_overlay_info *ovinfo_tab)
+{
+ struct of_overlay_info *ovinfo;
+ int i;
+
+ if (!ovinfo_tab || count < 0)
+ return -EINVAL;
+
+ /* do it in reverse */
+ for (i = count - 1; i >= 0; i--) {
+ ovinfo = &ovinfo_tab[i];
+
+ of_node_put(ovinfo->target);
+ of_node_put(ovinfo->overlay);
+ }
+ kfree(ovinfo_tab);
+
+ return 0;
+}
+
diff --git a/include/linux/of.h b/include/linux/of.h
index ab52243..8a908f0 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -667,4 +667,111 @@ static inline int of_resolve(struct device_node *resolve)

#endif

+/**
+ * Overlay support
+ */
+
+/**
+ * struct of_overlay_log_entry - Holds a DT log entry
+ * @node: list_head for the log list
+ * @action: notifier action
+ * @np: pointer to the device node affected
+ * @prop: pointer to the property affected
+ * @old_prop: hold a pointer to the original property
+ *
+ * Every modification of the device tree during application of the
+ * overlay is held in a list of of_overlay_log_entry structures.
+ * That way we can recover from a partial application, or we can
+ * revert the overlay properly.
+ */
+struct of_overlay_log_entry {
+ struct list_head node;
+ unsigned long action;
+ struct device_node *np;
+ struct property *prop;
+ struct property *old_prop;
+};
+
+/**
+ * struct of_overlay_device_entry - Holds an overlay device entry
+ * @node: list_head for the device list
+ * @np: device node pointer to the device node affected
+ * @pdev: pointer to the platform device affected
+ * @state: new device state
+ *
+ * When the overlay results in a device node's state to change this
+ * fact is recorded in a list of device entries. After the overlay
+ * is applied we can create/destroy the platform devices according
+ * to the new state of the live tree.
+ */
+struct of_overlay_device_entry {
+ struct list_head node;
+ struct device_node *np;
+ struct platform_device *pdev;
+ int state;
+};
+
+/**
+ * struct of_overlay_info - Holds a single overlay info
+ * @target: target of the overlay operation
+ * @overlay: pointer to the overlay contents node
+ * @lock: Lock to hold when accessing the lists
+ * @le_list: List of the overlay logs
+ * @de_list: List of the overlay records
+ * @notifier: of reconfiguration notifier
+ *
+ * Holds a single overlay state, including all the overlay logs &
+ * records.
+ */
+struct of_overlay_info {
+ struct device_node *target;
+ struct device_node *overlay;
+ struct mutex lock;
+ struct list_head le_list;
+ struct list_head de_list;
+ struct notifier_block notifier;
+};
+
+#ifdef CONFIG_OF_OVERLAY
+
+int of_overlay(int count, struct of_overlay_info *ovinfo_tab);
+int of_overlay_revert(int count, struct of_overlay_info *ovinfo_tab);
+
+int of_fill_overlay_info(struct device_node *info_node,
+ struct of_overlay_info *ovinfo);
+int of_build_overlay_info(struct device_node *tree,
+ int *cntp, struct of_overlay_info **ovinfop);
+int of_free_overlay_info(int cnt, struct of_overlay_info *ovinfo);
+
+#else
+
+static inline int of_overlay(int count, struct of_overlay_info *ovinfo_tab)
+{
+ return -ENOTSUPP;
+}
+
+static inline int of_overlay_revert(int count, struct of_overlay_info *ovinfo_tab)
+{
+ return -ENOTSUPP;
+}
+
+static inline int of_fill_overlay_info(struct device_node *info_node,
+ struct of_overlay_info *ovinfo)
+{
+ return -ENOTSUPP;
+}
+
+static inline int of_build_overlay_info(struct device_node *tree,
+ int *cntp, struct of_overlay_info **ovinfop)
+{
+ return -ENOTSUPP;
+}
+
+int of_free_overlay_info(int cnt, struct of_overlay_info *ovinfo)
+{
+ return -ENOTSUPP;
+}
+
+#endif
+
#endif /* _LINUX_OF_H */
--
1.7.12


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