Re: [PATCH 2/3] OF: Introduce DT overlay support.
From: Pantelis Antoniou
Date: Thu Nov 07 2013 - 02:10:20 EST
Hi Dinh,
On Nov 6, 2013, at 10:41 PM, Dinh Nguyen wrote:
> 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.
>
Thanks, fixed.
> Dinh
>> + return -ENOTSUPP;
>> +}
>> +
>> +#endif
>> +
>> #endif /* _LINUX_OF_H */
>
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