Hi Pantelis,
On 11/5/13 12:41 PM, Pantelis Antoniou wrote:
> 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.
>
> Note that the I2C client devices are 'special', as in they're not platform
> devices. They need to be registered with an I2C specific method.
>
> In general I2C is just no good platform device citizen and needs
> special casing.
>
> Signed-off-by: Pantelis Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx>
> ---
> Documentation/devicetree/overlay-notes.txt | 179 ++++++
> drivers/of/Kconfig | 10 +
> drivers/of/Makefile | 1 +
> drivers/of/overlay.c | 869 +++++++++++++++++++++++++++++
> include/linux/of.h | 113 ++++
> 5 files changed, 1172 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 2a00ae5..c2d5596 100644
> --- a/drivers/of/Kconfig
> +++ b/drivers/of/Kconfig
> @@ -83,4 +83,14 @@ 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 93da457..ca466e4 100644
> --- a/drivers/of/Makefile
> +++ b/drivers/of/Makefile
> @@ -10,3 +10,4 @@ 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..5bed1f4
> --- /dev/null
> +++ b/drivers/of/overlay.c
> @@ -0,0 +1,869 @@
> +/*
> + * Functions for working with device tree overlays
> + *
> + * Copyright (C) 2012 Pantelis Antoniou <panto@xxxxxxxxxxxxxxxxxxxxxxx>
> + * 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.
> + */
> +#undef DEBUG
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/i2c.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 *de;
> +
> + /* no need for locks, we'de under the ovinfo->lock */
> + list_for_each_entry(de, &ovinfo->de_list, node) {
> + if (de->np == node)
> + return de;
> + }
> + 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, struct i2c_client *client,
> + int prevstate, int state)
> +{
> + struct of_overlay_device_entry *de;
> + int fresh;
> +
> + /* check */
> + if (ovinfo == NULL)
> + return;
> +
> + fresh = 0;
> + de = of_overlay_device_entry_lookup(ovinfo, node);
> + if (de == NULL) {
> + de = kzalloc(sizeof(*de), GFP_KERNEL);
> + if (de == NULL) {
> + pr_err("%s: Failed to allocate\n", __func__);
> + return;
> + }
> + fresh = 1;
> + de->prevstate = -1;
> + }
> +
> + if (de->np == NULL)
> + de->np = of_node_get(node);
> + if (de->pdev == NULL && pdev)
> + de->pdev = of_dev_get(pdev);
> + if (de->client == NULL && client)
> + de->client = i2c_use_client(client);
> + if (fresh)
> + de->prevstate = prevstate;
> + de->state = state;
> +
> + if (fresh)
> + list_add_tail(&de->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)
> +{
> + struct of_overlay_info *ovinfo;
> + struct device_node *node;
> + struct property *prop, *sprop, *cprop;
> + struct of_prop_reconfig *pr;
> + struct platform_device *pdev;
> + struct i2c_client *client;
> + struct device_node *tnode;
> + int depth;
> + int prevstate, 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;
> + 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);
> + 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);
> +
> + /* come up with the device entry (if any) */
> + pdev = NULL;
> + client = NULL;
> + state = 0;
> + prevstate = 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:
> + prevstate = of_find_property(node, "compatible", NULL) &&
> + of_device_is_available(node);
> + state = 0;
> + pdev = of_find_device_by_node(node);
> + client = of_find_i2c_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;
> + }
> +
> + prevstate = of_find_property(node, "compatible", NULL) &&
> + of_device_is_available(node);
> + 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);
> + }
> +
> + /* find depth */
> + depth = 1;
> + tnode = node;
> + while (tnode != NULL && tnode != ovinfo->target) {
> + tnode = tnode->parent;
> + depth++;
> + }
> +
> + /* respect overlay's maximum depth */
> + if (ovinfo->device_depth != 0 && depth > ovinfo->device_depth) {
> + pr_debug("OF: skipping device creation for node=%s depth=%d\n",
> + node->name, depth);
> + goto out;
> + }
> +
> + if (state == 0) {
> + pdev = of_find_device_by_node(node);
> + client = of_find_i2c_device_by_node(node);
> + }
> +
> + of_overlay_device_entry_entry_add(ovinfo, node, pdev, client,
> + prevstate, state);
> +out:
> +
> + 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;
> +}
> +
> +static int of_overlay_device_entry_change(struct of_overlay_info *ovinfo,
> + struct of_overlay_device_entry *de, int revert)
> +{
> + struct i2c_adapter *adap = NULL;
> + struct i2c_client *client;
> + struct platform_device *pdev, *parent_pdev = NULL;
> + int state;
> +
> + state = !!de->state ^ !!revert;
> +
> + if (de->np && de->np->parent) {
> + pr_debug("%s: parent is %s\n",
> + __func__, de->np->parent->full_name);
> + adap = of_find_i2c_adapter_by_node(de->np->parent);
> + if (adap == NULL)
> + parent_pdev = of_find_device_by_node(de->np->parent);
> + }
> +
> + if (state) {
> +
> + /* try to see if it's an I2C client node */
> + if (adap == NULL) {
> +
> + pr_debug("%s: creating new platform device "
> + "new_node='%s' %p\n",
> + __func__, de->np->full_name, de->np);
> +
> + pdev = of_platform_device_create(de->np, NULL,
> + parent_pdev ? &parent_pdev->dev : NULL);
> + if (pdev == NULL) {
> + pr_warn("%s: Failed to create platform device "
> + "for '%s'\n",
> + __func__, de->np->full_name);
> + } else
> + de->pdev = pdev;
> +
> + } else {
> +
> + client = of_find_i2c_device_by_node(de->np);
> + if (client != NULL) {
> + /* bus already created the device; do nothing */
> + put_device(&client->dev);
> + } else {
> + pr_debug("%s: creating new i2c_client device "
> + "new_node='%s' %p\n",
> + __func__, de->np->full_name, de->np);
> +
> + client = of_i2c_register_device(adap, de->np);
> +
> + if (client == NULL) {
> + pr_warn("%s: Failed to create i2c client device "
> + "for '%s'\n",
> + __func__, de->np->full_name);
> + } else
> + de->client = client;
> + }
> + }
> +
> + } else {
> +
> + if (de->pdev) {
> + pr_debug("%s: removing pdev %s\n", __func__,
> + dev_name(&de->pdev->dev));
> + platform_device_unregister(de->pdev);
> + de->pdev = NULL;
> + }
> +
> + if (de->client) {
> + pr_debug("%s: removing i2c client %s\n", __func__,
> + dev_name(&de->client->dev));
> + i2c_unregister_device(de->client);
> + de->client = NULL;
> + }
> + }
> +
> + if (adap)
> + put_device(&adap->dev);
> +
> + if (parent_pdev)
> + of_dev_put(parent_pdev);
> +
> + 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 *de, *den;
> + struct of_overlay_log_entry *le, *len;
> + struct property *prop, **propp;
> + 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(de, den, &ovinfo->de_list, node) {
> + of_overlay_device_entry_change(ovinfo, de, 1);
> + of_node_put(de->np);
> + list_del(&de->node);
> + kfree(de);
> + }
> +
> + 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) */
> + raw_spin_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;
> + raw_spin_unlock_irqrestore(&devtree_lock,
> + flags);
> + } else {
> + raw_spin_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 *de, *den;
> +
> + 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(de, den, &ovinfo->de_list, node) {
> +
> + /* no state change? just remove this entry */
> + if (de->prevstate == de->state) {
> + of_node_put(de->np);
> + list_del(&de->node);
> + kfree(de);
> + } else {
> + of_overlay_device_entry_change(ovinfo, de, 0);
> + }
> + }
> +
> + 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;
> +
> + ret = of_property_read_u32(info_node, "depth", &val);
> + if (ret == 0)
> + ovinfo->device_depth = val;
> + else
> + ovinfo->device_depth = 0;
> +
> +
> + 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 22d42e5..d9c8130 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -23,6 +23,7 @@
> #include <linux/spinlock.h>
> #include <linux/topology.h>
> #include <linux/notifier.h>
> +#include <linux/i2c.h>
>
> #include <asm/byteorder.h>
> #include <asm/errno.h>
> @@ -738,4 +739,116 @@ 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
> + * @client: pointer to the I2C client device affected
> + * @state: new device state
> + * @prevstate: previous 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;
> + struct i2c_client *client;
> + int prevstate;
> + 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;
> + int device_depth;
> +};
> +
> +#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)
> +{
This needs a static inline, otherwise I get a build failure if
CONFIG_OF_OVERLAY is not set.
Dinh
> + return -ENOTSUPP;
> +}
> +
> +#endif
> +
> #endif /* _LINUX_OF_H */
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