of: Transactional DT support.

Introducing DT transactional support.

A DT transaction is a method which allows one to apply changes
in the live tree, in such a way that either the full set of changes
take effect, or the state of the tree can be rolled-back to the
state it was before it was attempted. An applied transaction
can be rolled-back at any time.

Documentation is in
	Documentation/devicetree/changesets.txt

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[glikely: Removed device notifiers and reworked to be more consistent]
Signed-off-by: Grant Likely <grant.likely@linaro.org>

6 files changed, 530 insertions, 0 deletions

diff --git a/Documentation/devicetree/changesets.txt b/Documentation/devicetree/changesets.txt
new file mode 100644
index 000000000000..935ba5acc34e
--- /dev/null
+++ b/Documentation/devicetree/changesets.txt
@@ -0,0 +1,40 @@
+A DT changeset is a method which allows one to apply changes
+in the live tree in such a way that either the full set of changes
+will be applied, or none of them will be. If an error occurs partway
+through applying the changeset, then the tree will be rolled back to the
+previous state. A changeset can also be removed after it has been
+applied.
+
+When a changeset is applied, all of the changes get applied to the tree
+at once before emitting OF_RECONFIG notifiers. This is so that the
+receiver sees a complete and consistent state of the tree when it
+receives the notifier.
+
+The sequence of a changeset is as follows.
+
+1. of_changeset_init() - initializes a changeset
+
+2. A number of DT tree change calls, of_changeset_attach_node(),
+of_changeset_detach_node(), of_changeset_add_property(),
+of_changeset_remove_property, of_changeset_update_property() to prepare
+a set of changes. No changes to the active tree are made at this point.
+All the change operations are recorded in the of_changeset 'entries'
+list.
+
+3. mutex_lock(of_mutex) - starts a changeset; The global of_mutex
+ensures there can only be one editor at a time.
+
+4. of_changeset_apply() - Apply the changes to the tree. Either the
+entire changeset will get applied, or if there is an error the tree will
+be restored to the previous state
+
+5. mutex_unlock(of_mutex) - All operations complete, release the mutex
+
+If a successfully applied changeset needs to be removed, it can be done
+with the following sequence.
+
+1. mutex_lock(of_mutex)
+
+2. of_changeset_revert()
+
+3. mutex_unlock(of_mutex)
diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index 7bd5501736a6..c1002b7be786 100644
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -314,3 +314,347 @@ struct device_node *__of_node_alloc(const char *full_name, gfp_t allocflags)
         kfree(node);
         return NULL;
 }
+
+static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
+{
+        of_node_put(ce->np);
+        list_del(&ce->node);
+        kfree(ce);
+}
+
+#ifdef DEBUG
+static void __of_changeset_entry_dump(struct of_changeset_entry *ce)
+{
+        switch (ce->action) {
+        case OF_RECONFIG_ADD_PROPERTY:
+                pr_debug("%p: %s %s/%s\n",
+                        ce, "ADD_PROPERTY   ", ce->np->full_name,
+                        ce->prop->name);
+                break;
+        case OF_RECONFIG_REMOVE_PROPERTY:
+                pr_debug("%p: %s %s/%s\n",
+                        ce, "REMOVE_PROPERTY", ce->np->full_name,
+                        ce->prop->name);
+                break;
+        case OF_RECONFIG_UPDATE_PROPERTY:
+                pr_debug("%p: %s %s/%s\n",
+                        ce, "UPDATE_PROPERTY", ce->np->full_name,
+                        ce->prop->name);
+                break;
+        case OF_RECONFIG_ATTACH_NODE:
+                pr_debug("%p: %s %s\n",
+                        ce, "ATTACH_NODE    ", ce->np->full_name);
+                break;
+        case OF_RECONFIG_DETACH_NODE:
+                pr_debug("%p: %s %s\n",
+                        ce, "DETACH_NODE    ", ce->np->full_name);
+                break;
+        }
+}
+#else
+static inline void __of_changeset_entry_dump(struct of_changeset_entry *ce)
+{
+        /* empty */
+}
+#endif
+
+static void __of_changeset_entry_invert(struct of_changeset_entry *ce,
+                                          struct of_changeset_entry *rce)
+{
+        memcpy(rce, ce, sizeof(*rce));
+
+        switch (ce->action) {
+        case OF_RECONFIG_ATTACH_NODE:
+                rce->action = OF_RECONFIG_DETACH_NODE;
+                break;
+        case OF_RECONFIG_DETACH_NODE:
+                rce->action = OF_RECONFIG_ATTACH_NODE;
+                break;
+        case OF_RECONFIG_ADD_PROPERTY:
+                rce->action = OF_RECONFIG_REMOVE_PROPERTY;
+                break;
+        case OF_RECONFIG_REMOVE_PROPERTY:
+                rce->action = OF_RECONFIG_ADD_PROPERTY;
+                break;
+        case OF_RECONFIG_UPDATE_PROPERTY:
+                rce->old_prop = ce->prop;
+                rce->prop = ce->old_prop;
+                break;
+        }
+}
+
+static void __of_changeset_entry_notify(struct of_changeset_entry *ce, bool revert)
+{
+        struct of_changeset_entry ce_inverted;
+        int ret;
+
+        if (revert) {
+                __of_changeset_entry_invert(ce, &ce_inverted);
+                ce = &ce_inverted;
+        }
+
+        switch (ce->action) {
+        case OF_RECONFIG_ATTACH_NODE:
+        case OF_RECONFIG_DETACH_NODE:
+                ret = of_reconfig_notify(ce->action, ce->np);
+                break;
+        case OF_RECONFIG_ADD_PROPERTY:
+        case OF_RECONFIG_REMOVE_PROPERTY:
+        case OF_RECONFIG_UPDATE_PROPERTY:
+                ret = of_property_notify(ce->action, ce->np, ce->prop, ce->old_prop);
+                break;
+        default:
+                pr_err("%s: invalid devicetree changeset action: %i\n", __func__,
+                        (int)ce->action);
+                return;
+        }
+
+        if (ret)
+                pr_err("%s: notifier error @%s\n", __func__, ce->np->full_name);
+}
+
+static int __of_changeset_entry_apply(struct of_changeset_entry *ce)
+{
+        struct property *old_prop, **propp;
+        unsigned long flags;
+        int ret = 0;
+
+        __of_changeset_entry_dump(ce);
+
+        raw_spin_lock_irqsave(&devtree_lock, flags);
+        switch (ce->action) {
+        case OF_RECONFIG_ATTACH_NODE:
+                __of_attach_node(ce->np);
+                break;
+        case OF_RECONFIG_DETACH_NODE:
+                __of_detach_node(ce->np);
+                break;
+        case OF_RECONFIG_ADD_PROPERTY:
+                /* If the property is in deadprops then it must be removed */
+                for (propp = &ce->np->deadprops; *propp; propp = &(*propp)->next) {
+                        if (*propp == ce->prop) {
+                                *propp = ce->prop->next;
+                                ce->prop->next = NULL;
+                                break;
+                        }
+                }
+
+                ret = __of_add_property(ce->np, ce->prop);
+                if (ret) {
+                        pr_err("%s: add_property failed @%s/%s\n",
+                                __func__, ce->np->full_name,
+                                ce->prop->name);
+                        break;
+                }
+                break;
+        case OF_RECONFIG_REMOVE_PROPERTY:
+                ret = __of_remove_property(ce->np, ce->prop);
+                if (ret) {
+                        pr_err("%s: remove_property failed @%s/%s\n",
+                                __func__, ce->np->full_name,
+                                ce->prop->name);
+                        break;
+                }
+                break;
+
+        case OF_RECONFIG_UPDATE_PROPERTY:
+                /* If the property is in deadprops then it must be removed */
+                for (propp = &ce->np->deadprops; *propp; propp = &(*propp)->next) {
+                        if (*propp == ce->prop) {
+                                *propp = ce->prop->next;
+                                ce->prop->next = NULL;
+                                break;
+                        }
+                }
+
+                ret = __of_update_property(ce->np, ce->prop, &old_prop);
+                if (ret) {
+                        pr_err("%s: update_property failed @%s/%s\n",
+                                __func__, ce->np->full_name,
+                                ce->prop->name);
+                        break;
+                }
+                break;
+        default:
+                ret = -EINVAL;
+        }
+        raw_spin_unlock_irqrestore(&devtree_lock, flags);
+
+        if (ret)
+                return ret;
+
+        switch (ce->action) {
+        case OF_RECONFIG_ATTACH_NODE:
+                __of_attach_node_sysfs(ce->np);
+                break;
+        case OF_RECONFIG_DETACH_NODE:
+                __of_detach_node_sysfs(ce->np);
+                break;
+        case OF_RECONFIG_ADD_PROPERTY:
+                /* ignore duplicate names */
+                __of_add_property_sysfs(ce->np, ce->prop);
+                break;
+        case OF_RECONFIG_REMOVE_PROPERTY:
+                __of_remove_property_sysfs(ce->np, ce->prop);
+                break;
+        case OF_RECONFIG_UPDATE_PROPERTY:
+                __of_update_property_sysfs(ce->np, ce->prop, ce->old_prop);
+                break;
+        }
+
+        return 0;
+}
+
+static inline int __of_changeset_entry_revert(struct of_changeset_entry *ce)
+{
+        struct of_changeset_entry ce_inverted;
+
+        __of_changeset_entry_invert(ce, &ce_inverted);
+        return __of_changeset_entry_apply(&ce_inverted);
+}
+
+/**
+ * of_changeset_init - Initialize a changeset for use
+ *
+ * @ocs:        changeset pointer
+ *
+ * Initialize a changeset structure
+ */
+void of_changeset_init(struct of_changeset *ocs)
+{
+        memset(ocs, 0, sizeof(*ocs));
+        INIT_LIST_HEAD(&ocs->entries);
+}
+
+/**
+ * of_changeset_destroy - Destroy a changeset
+ *
+ * @ocs:        changeset pointer
+ *
+ * Destroys a changeset. Note that if a changeset is applied,
+ * its changes to the tree cannot be reverted.
+ */
+void of_changeset_destroy(struct of_changeset *ocs)
+{
+        struct of_changeset_entry *ce, *cen;
+
+        list_for_each_entry_safe_reverse(ce, cen, &ocs->entries, node)
+                __of_changeset_entry_destroy(ce);
+}
+
+/**
+ * of_changeset_apply - Applies a changeset
+ *
+ * @ocs:        changeset pointer
+ *
+ * Applies a changeset to the live tree.
+ * Any side-effects of live tree state changes are applied here on
+ * sucess, like creation/destruction of devices and side-effects
+ * like creation of sysfs properties and directories.
+ * Returns 0 on success, a negative error value in case of an error.
+ * On error the partially applied effects are reverted.
+ */
+int of_changeset_apply(struct of_changeset *ocs)
+{
+        struct of_changeset_entry *ce;
+        int ret;
+
+        /* perform the rest of the work */
+        pr_debug("of_changeset: applying...\n");
+        list_for_each_entry(ce, &ocs->entries, node) {
+                ret = __of_changeset_entry_apply(ce);
+                if (ret) {
+                        pr_err("%s: Error applying changeset (%d)\n", __func__, ret);
+                        list_for_each_entry_continue_reverse(ce, &ocs->entries, node)
+                                __of_changeset_entry_revert(ce);
+                        return ret;
+                }
+        }
+        pr_debug("of_changeset: applied, emitting notifiers.\n");
+
+        /* drop the global lock while emitting notifiers */
+        mutex_unlock(&of_mutex);
+        list_for_each_entry(ce, &ocs->entries, node)
+                __of_changeset_entry_notify(ce, 0);
+        mutex_lock(&of_mutex);
+        pr_debug("of_changeset: notifiers sent.\n");
+
+        return 0;
+}
+
+/**
+ * of_changeset_revert - Reverts an applied changeset
+ *
+ * @ocs:        changeset pointer
+ *
+ * Reverts a changeset returning the state of the tree to what it
+ * was before the application.
+ * Any side-effects like creation/destruction of devices and
+ * removal of sysfs properties and directories are applied.
+ * Returns 0 on success, a negative error value in case of an error.
+ */
+int of_changeset_revert(struct of_changeset *ocs)
+{
+        struct of_changeset_entry *ce;
+        int ret;
+
+        pr_debug("of_changeset: reverting...\n");
+        list_for_each_entry_reverse(ce, &ocs->entries, node) {
+                ret = __of_changeset_entry_revert(ce);
+                if (ret) {
+                        pr_err("%s: Error reverting changeset (%d)\n", __func__, ret);
+                        list_for_each_entry_continue(ce, &ocs->entries, node)
+                                __of_changeset_entry_apply(ce);
+                        return ret;
+                }
+        }
+        pr_debug("of_changeset: reverted, emitting notifiers.\n");
+
+        /* drop the global lock while emitting notifiers */
+        mutex_unlock(&of_mutex);
+        list_for_each_entry_reverse(ce, &ocs->entries, node)
+                __of_changeset_entry_notify(ce, 1);
+        mutex_lock(&of_mutex);
+        pr_debug("of_changeset: notifiers sent.\n");
+
+        return 0;
+}
+
+/**
+ * of_changeset_action - Perform a changeset action
+ *
+ * @ocs:        changeset pointer
+ * @action:     action to perform
+ * @np:         Pointer to device node
+ * @prop:       Pointer to property
+ *
+ * On action being one of:
+ * + OF_RECONFIG_ATTACH_NODE
+ * + OF_RECONFIG_DETACH_NODE,
+ * + OF_RECONFIG_ADD_PROPERTY
+ * + OF_RECONFIG_REMOVE_PROPERTY,
+ * + OF_RECONFIG_UPDATE_PROPERTY
+ * Returns 0 on success, a negative error value in case of an error.
+ */
+int of_changeset_action(struct of_changeset *ocs, unsigned long action,
+                struct device_node *np, struct property *prop)
+{
+        struct of_changeset_entry *ce;
+
+        ce = kzalloc(sizeof(*ce), GFP_KERNEL);
+        if (!ce) {
+                pr_err("%s: Failed to allocate\n", __func__);
+                return -ENOMEM;
+        }
+        /* get a reference to the node */
+        ce->action = action;
+        ce->np = of_node_get(np);
+        ce->prop = prop;
+
+        if (action == OF_RECONFIG_UPDATE_PROPERTY && prop)
+                ce->old_prop = of_find_property(np, prop->name, NULL);
+
+        /* add it to the list */
+        list_add_tail(&ce->node, &ocs->entries);
+        return 0;
+}
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index f69ccb1fa308..858e0a5d9a11 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -81,4 +81,13 @@ extern int __of_attach_node_sysfs(struct device_node *np);
 extern void __of_detach_node(struct device_node *np);
 extern void __of_detach_node_sysfs(struct device_node *np);
 
+/* iterators for transactions, used for overlays */
+/* forward iterator */
+#define for_each_transaction_entry(_oft, _te) \
+        list_for_each_entry(_te, &(_oft)->te_list, node)
+
+/* reverse iterator */
+#define for_each_transaction_entry_reverse(_oft, _te) \
+        list_for_each_entry_reverse(_te, &(_oft)->te_list, node)
+
 #endif /* _LINUX_OF_PRIVATE_H */
diff --git a/drivers/of/selftest.c b/drivers/of/selftest.c
index ee2166f0f36a..04e39a183e53 100644
--- a/drivers/of/selftest.c
+++ b/drivers/of/selftest.c
@@ -293,6 +293,56 @@ static void __init of_selftest_property_copy(void)
 #endif
 }
 
+static void __init of_selftest_changeset(void)
+{
+#ifdef CONFIG_OF_DYNAMIC
+        struct property *ppadd, padd = { .name = "prop-add", .length = 0, .value = "" };
+        struct property *ppupdate, pupdate = { .name = "prop-update", .length = 5, .value = "abcd" };
+        struct property *ppremove;
+        struct device_node *n1, *n2, *n21, *nremove, *parent;
+        struct of_changeset chgset;
+
+        of_changeset_init(&chgset);
+        n1 = __of_node_alloc("/testcase-data/changeset/n1", GFP_KERNEL);
+        selftest(n1, "testcase setup failure\n");
+        n2 = __of_node_alloc("/testcase-data/changeset/n2", GFP_KERNEL);
+        selftest(n2, "testcase setup failure\n");
+        n21 = __of_node_alloc("/testcase-data/changeset/n2/n21", GFP_KERNEL);
+        selftest(n21, "testcase setup failure %p\n", n21);
+        nremove = of_find_node_by_path("/testcase-data/changeset/node-remove");
+        selftest(nremove, "testcase setup failure\n");
+        ppadd = __of_prop_dup(&padd, GFP_KERNEL);
+        selftest(ppadd, "testcase setup failure\n");
+        ppupdate = __of_prop_dup(&pupdate, GFP_KERNEL);
+        selftest(ppupdate, "testcase setup failure\n");
+        parent = nremove->parent;
+        n1->parent = parent;
+        n2->parent = parent;
+        n21->parent = n2;
+        n2->child = n21;
+        ppremove = of_find_property(parent, "prop-remove", NULL);
+        selftest(ppremove, "failed to find removal prop");
+
+        of_changeset_init(&chgset);
+        selftest(!of_changeset_attach_node(&chgset, n1), "fail attach n1\n");
+        selftest(!of_changeset_attach_node(&chgset, n2), "fail attach n2\n");
+        selftest(!of_changeset_detach_node(&chgset, nremove), "fail remove node\n");
+        selftest(!of_changeset_attach_node(&chgset, n21), "fail attach n21\n");
+        selftest(!of_changeset_add_property(&chgset, parent, ppadd), "fail add prop\n");
+        selftest(!of_changeset_update_property(&chgset, parent, ppupdate), "fail update prop\n");
+        selftest(!of_changeset_remove_property(&chgset, parent, ppremove), "fail remove prop\n");
+        mutex_lock(&of_mutex);
+        selftest(!of_changeset_apply(&chgset), "apply failed\n");
+        mutex_unlock(&of_mutex);
+
+        mutex_lock(&of_mutex);
+        selftest(!of_changeset_revert(&chgset), "revert failed\n");
+        mutex_unlock(&of_mutex);
+
+        of_changeset_destroy(&chgset);
+#endif
+}
+
 static void __init of_selftest_parse_interrupts(void)
 {
         struct device_node *np;
@@ -561,6 +611,7 @@ static int __init of_selftest(void)
         of_selftest_parse_phandle_with_args();
         of_selftest_property_match_string();
         of_selftest_property_copy();
+        of_selftest_changeset();
         of_selftest_parse_interrupts();
         of_selftest_parse_interrupts_extended();
         of_selftest_match_node();
diff --git a/drivers/of/testcase-data/testcases.dtsi b/drivers/of/testcase-data/testcases.dtsi
index 6d8d980ac858..669bb07df142 100644
--- a/drivers/of/testcase-data/testcases.dtsi
+++ b/drivers/of/testcase-data/testcases.dtsi
@@ -1,3 +1,13 @@
+/ {
+        testcase-data {
+                changeset {
+                        prop-update = "hello";
+                        prop-remove = "world";
+                        node-remove {
+                        };
+                };
+        };
+};
 #include "tests-phandle.dtsi"
 #include "tests-interrupts.dtsi"
 #include "tests-match.dtsi"
diff --git a/include/linux/of.h b/include/linux/of.h
index 400f18cb4fff..bc91fbb13ce8 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -786,4 +786,80 @@ typedef void (*of_init_fn_1)(struct device_node *);
 #define OF_DECLARE_2(table, name, compat, fn) \
                 _OF_DECLARE(table, name, compat, fn, of_init_fn_2)
 
+/**
+ * struct of_changeset_entry    - Holds a changeset 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 a changeset
+ * is held in a list of of_changeset_entry structures.
+ * That way we can recover from a partial application, or we can
+ * revert the changeset
+ */
+struct of_changeset_entry {
+        struct list_head node;
+        unsigned long action;
+        struct device_node *np;
+        struct property *prop;
+        struct property *old_prop;
+};
+
+/**
+ * struct of_changeset - changeset tracker structure
+ *
+ * @entries:    list_head for the changeset entries
+ *
+ * changesets are a convenient way to apply bulk changes to the
+ * live tree. In case of an error, changes are rolled-back.
+ * changesets live on after initial application, and if not
+ * destroyed after use, they can be reverted in one single call.
+ */
+struct of_changeset {
+        struct list_head entries;
+};
+
+#ifdef CONFIG_OF_DYNAMIC
+extern void of_changeset_init(struct of_changeset *ocs);
+extern void of_changeset_destroy(struct of_changeset *ocs);
+extern int of_changeset_apply(struct of_changeset *ocs);
+extern int of_changeset_revert(struct of_changeset *ocs);
+extern int of_changeset_action(struct of_changeset *ocs,
+                unsigned long action, struct device_node *np,
+                struct property *prop);
+
+static inline int of_changeset_attach_node(struct of_changeset *ocs,
+                struct device_node *np)
+{
+        return of_changeset_action(ocs, OF_RECONFIG_ATTACH_NODE, np, NULL);
+}
+
+static inline int of_changeset_detach_node(struct of_changeset *ocs,
+                struct device_node *np)
+{
+        return of_changeset_action(ocs, OF_RECONFIG_DETACH_NODE, np, NULL);
+}
+
+static inline int of_changeset_add_property(struct of_changeset *ocs,
+                struct device_node *np, struct property *prop)
+{
+        return of_changeset_action(ocs, OF_RECONFIG_ADD_PROPERTY, np, prop);
+}
+
+static inline int of_changeset_remove_property(struct of_changeset *ocs,
+                struct device_node *np, struct property *prop)
+{
+        return of_changeset_action(ocs, OF_RECONFIG_REMOVE_PROPERTY, np, prop);
+}
+
+static inline int of_changeset_update_property(struct of_changeset *ocs,
+                struct device_node *np, struct property *prop)
+{
+        return of_changeset_action(ocs, OF_RECONFIG_UPDATE_PROPERTY, np, prop);
+}
+#endif
+
 #endif /* _LINUX_OF_H */