// SPDX-License-Identifier: GPL-2.0 /* * Functions for working with device tree overlays * * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com> * Copyright (C) 2012 Texas Instruments Inc. */ #define pr_fmt(fmt) "OF: overlay: " fmt #include <linux/kernel.h> #include <linux/module.h> #include <linux/of.h> #include <linux/of_device.h> #include <linux/of_fdt.h> #include <linux/string.h> #include <linux/ctype.h> #include <linux/errno.h> #include <linux/slab.h> #include <linux/libfdt.h> #include <linux/err.h> #include <linux/idr.h> #include "of_private.h" /** * struct fragment - info about fragment nodes in overlay expanded device tree * @target: target of the overlay operation * @overlay: pointer to the __overlay__ node */ struct fragment { struct device_node *target; struct device_node *overlay; }; /** * struct overlay_changeset * @id: changeset identifier * @ovcs_list: list on which we are located * @fdt: FDT that was unflattened to create @overlay_tree * @overlay_tree: expanded device tree that contains the fragment nodes * @count: count of fragment structures * @fragments: fragment nodes in the overlay expanded device tree * @symbols_fragment: last element of @fragments[] is the __symbols__ node * @cset: changeset to apply fragments to live device tree */ struct overlay_changeset { int id; struct list_head ovcs_list; const void *fdt; struct device_node *overlay_tree; int count; struct fragment *fragments; bool symbols_fragment; struct of_changeset cset; }; /* flags are sticky - once set, do not reset */ static int devicetree_state_flags; #define DTSF_APPLY_FAIL 0x01 #define DTSF_REVERT_FAIL 0x02 /* * If a changeset apply or revert encounters an error, an attempt will * be made to undo partial changes, but may fail. If the undo fails * we do not know the state of the devicetree. */ static int devicetree_corrupt(void) { return devicetree_state_flags & (DTSF_APPLY_FAIL | DTSF_REVERT_FAIL); } static int build_changeset_next_level(struct overlay_changeset *ovcs, struct device_node *target_node, const struct device_node *overlay_node); /* * of_resolve_phandles() finds the largest phandle in the live tree. * of_overlay_apply() may add a larger phandle to the live tree. * Do not allow race between two overlays being applied simultaneously: * mutex_lock(&of_overlay_phandle_mutex) * of_resolve_phandles() * of_overlay_apply() * mutex_unlock(&of_overlay_phandle_mutex) */ static DEFINE_MUTEX(of_overlay_phandle_mutex); void of_overlay_mutex_lock(void) { mutex_lock(&of_overlay_phandle_mutex); } void of_overlay_mutex_unlock(void) { mutex_unlock(&of_overlay_phandle_mutex); } static LIST_HEAD(ovcs_list); static DEFINE_IDR(ovcs_idr); static BLOCKING_NOTIFIER_HEAD(overlay_notify_chain); /** * of_overlay_notifier_register() - Register notifier for overlay operations * @nb: Notifier block to register * * Register for notification on overlay operations on device tree nodes. The * reported actions definied by @of_reconfig_change. The notifier callback * furthermore receives a pointer to the affected device tree node. * * Note that a notifier callback is not supposed to store pointers to a device * tree node or its content beyond @OF_OVERLAY_POST_REMOVE corresponding to the * respective node it received. */ int of_overlay_notifier_register(struct notifier_block *nb) { return blocking_notifier_chain_register(&overlay_notify_chain, nb); } EXPORT_SYMBOL_GPL(of_overlay_notifier_register); /** * of_overlay_notifier_register() - Unregister notifier for overlay operations * @nb: Notifier block to unregister */ int of_overlay_notifier_unregister(struct notifier_block *nb) { return blocking_notifier_chain_unregister(&overlay_notify_chain, nb); } EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister); static char *of_overlay_action_name[] = { "pre-apply", "post-apply", "pre-remove", "post-remove", }; static int overlay_notify(struct overlay_changeset *ovcs, enum of_overlay_notify_action action) { struct of_overlay_notify_data nd; int i, ret; for (i = 0; i < ovcs->count; i++) { struct fragment *fragment = &ovcs->fragments[i]; nd.target = fragment->target; nd.overlay = fragment->overlay; ret = blocking_notifier_call_chain(&overlay_notify_chain, action, &nd); if (ret == NOTIFY_OK || ret == NOTIFY_STOP) return 0; if (ret) { ret = notifier_to_errno(ret); pr_err("overlay changeset %s notifier error %d, target: %pOF\n", of_overlay_action_name[action], ret, nd.target); return ret; } } return 0; } /* * The values of properties in the "/__symbols__" node are paths in * the ovcs->overlay_tree. When duplicating the properties, the paths * need to be adjusted to be the correct path for the live device tree. * * The paths refer to a node in the subtree of a fragment node's "__overlay__" * node, for example "/fragment@0/__overlay__/symbol_path_tail", * where symbol_path_tail can be a single node or it may be a multi-node path. * * The duplicated property value will be modified by replacing the * "/fragment_name/__overlay/" portion of the value with the target * path from the fragment node. */ static struct property *dup_and_fixup_symbol_prop( struct overlay_changeset *ovcs, const struct property *prop) { struct fragment *fragment; struct property *new_prop; struct device_node *fragment_node; struct device_node *overlay_node; const char *path; const char *path_tail; const char *target_path; int k; int overlay_name_len; int path_len; int path_tail_len; int target_path_len; if (!prop->value) return NULL; if (strnlen(prop->value, prop->length) >= prop->length) return NULL; path = prop->value; path_len = strlen(path); if (path_len < 1) return NULL; fragment_node = __of_find_node_by_path(ovcs->overlay_tree, path + 1); overlay_node = __of_find_node_by_path(fragment_node, "__overlay__/"); of_node_put(fragment_node); of_node_put(overlay_node); for (k = 0; k < ovcs->count; k++) { fragment = &ovcs->fragments[k]; if (fragment->overlay == overlay_node) break; } if (k >= ovcs->count) return NULL; overlay_name_len = snprintf(NULL, 0, "%pOF", fragment->overlay); if (overlay_name_len > path_len) return NULL; path_tail = path + overlay_name_len; path_tail_len = strlen(path_tail); target_path = kasprintf(GFP_KERNEL, "%pOF", fragment->target); if (!target_path) return NULL; target_path_len = strlen(target_path); new_prop = kzalloc(sizeof(*new_prop), GFP_KERNEL); if (!new_prop) goto err_free_target_path; new_prop->name = kstrdup(prop->name, GFP_KERNEL); new_prop->length = target_path_len + path_tail_len + 1; new_prop->value = kzalloc(new_prop->length, GFP_KERNEL); if (!new_prop->name || !new_prop->value) goto err_free_new_prop; strcpy(new_prop->value, target_path); strcpy(new_prop->value + target_path_len, path_tail); of_property_set_flag(new_prop, OF_DYNAMIC); return new_prop; err_free_new_prop: kfree(new_prop->name); kfree(new_prop->value); kfree(new_prop); err_free_target_path: kfree(target_path); return NULL; } /** * add_changeset_property() - add @overlay_prop to overlay changeset * @ovcs: overlay changeset * @target_node: where to place @overlay_prop in live tree * @overlay_prop: property to add or update, from overlay tree * @is_symbols_prop: 1 if @overlay_prop is from node "/__symbols__" * * If @overlay_prop does not already exist in @target_node, add changeset entry * to add @overlay_prop in @target_node, else add changeset entry to update * value of @overlay_prop. * * Some special properties are not updated (no error returned). * * Update of property in symbols node is not allowed. * * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid @overlay. */ static int add_changeset_property(struct overlay_changeset *ovcs, struct device_node *target_node, struct property *overlay_prop, bool is_symbols_prop) { struct property *new_prop = NULL, *prop; int ret = 0; prop = of_find_property(target_node, overlay_prop->name, NULL); if (!of_prop_cmp(overlay_prop->name, "name") || !of_prop_cmp(overlay_prop->name, "phandle") || !of_prop_cmp(overlay_prop->name, "linux,phandle")) return 0; if (is_symbols_prop) { if (prop) return -EINVAL; new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop); } else { new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL); } if (!new_prop) return -ENOMEM; if (!prop) ret = of_changeset_add_property(&ovcs->cset, target_node, new_prop); else ret = of_changeset_update_property(&ovcs->cset, target_node, new_prop); if (ret) { kfree(new_prop->name); kfree(new_prop->value); kfree(new_prop); } return ret; } /** * add_changeset_node() - add @node (and children) to overlay changeset * @ovcs: overlay changeset * @target_node: where to place @node in live tree * @node: node from within overlay device tree fragment * * If @node does not already exist in @target_node, add changeset entry * to add @node in @target_node. * * If @node already exists in @target_node, and the existing node has * a phandle, the overlay node is not allowed to have a phandle. * * If @node has child nodes, add the children recursively via * build_changeset_next_level(). * * NOTE_1: A live devicetree created from a flattened device tree (FDT) will * not contain the full path in node->full_name. Thus an overlay * created from an FDT also will not contain the full path in * node->full_name. However, a live devicetree created from Open * Firmware may have the full path in node->full_name. * * add_changeset_node() follows the FDT convention and does not include * the full path in node->full_name. Even though it expects the overlay * to not contain the full path, it uses kbasename() to remove the * full path should it exist. It also uses kbasename() in comparisons * to nodes in the live devicetree so that it can apply an overlay to * a live devicetree created from Open Firmware. * * NOTE_2: Multiple mods of created nodes not supported. * If more than one fragment contains a node that does not already exist * in the live tree, then for each fragment of_changeset_attach_node() * will add a changeset entry to add the node. When the changeset is * applied, __of_attach_node() will attach the node twice (once for * each fragment). At this point the device tree will be corrupted. * * TODO: add integrity check to ensure that multiple fragments do not * create the same node. * * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid @overlay. */ static int add_changeset_node(struct overlay_changeset *ovcs, struct device_node *target_node, struct device_node *node) { const char *node_kbasename; struct device_node *tchild; int ret = 0; node_kbasename = kbasename(node->full_name); for_each_child_of_node(target_node, tchild) if (!of_node_cmp(node_kbasename, kbasename(tchild->full_name))) break; if (!tchild) { tchild = __of_node_dup(node, node_kbasename); if (!tchild) return -ENOMEM; tchild->parent = target_node; ret = of_changeset_attach_node(&ovcs->cset, tchild); if (ret) return ret; return build_changeset_next_level(ovcs, tchild, node); } if (node->phandle && tchild->phandle) ret = -EINVAL; else ret = build_changeset_next_level(ovcs, tchild, node); of_node_put(tchild); return ret; } /** * build_changeset_next_level() - add level of overlay changeset * @ovcs: overlay changeset * @target_node: where to place @overlay_node in live tree * @overlay_node: node from within an overlay device tree fragment * * Add the properties (if any) and nodes (if any) from @overlay_node to the * @ovcs->cset changeset. If an added node has child nodes, they will * be added recursively. * * Do not allow symbols node to have any children. * * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid @overlay_node. */ static int build_changeset_next_level(struct overlay_changeset *ovcs, struct device_node *target_node, const struct device_node *overlay_node) { struct device_node *child; struct property *prop; int ret; for_each_property_of_node(overlay_node, prop) { ret = add_changeset_property(ovcs, target_node, prop, 0); if (ret) { pr_debug("Failed to apply prop @%pOF/%s, err=%d\n", target_node, prop->name, ret); return ret; } } for_each_child_of_node(overlay_node, child) { ret = add_changeset_node(ovcs, target_node, child); if (ret) { pr_debug("Failed to apply node @%pOF/%s, err=%d\n", target_node, child->name, ret); of_node_put(child); return ret; } } return 0; } /* * Add the properties from __overlay__ node to the @ovcs->cset changeset. */ static int build_changeset_symbols_node(struct overlay_changeset *ovcs, struct device_node *target_node, const struct device_node *overlay_symbols_node) { struct property *prop; int ret; for_each_property_of_node(overlay_symbols_node, prop) { ret = add_changeset_property(ovcs, target_node, prop, 1); if (ret) { pr_debug("Failed to apply prop @%pOF/%s, err=%d\n", target_node, prop->name, ret); return ret; } } return 0; } /** * build_changeset() - populate overlay changeset in @ovcs from @ovcs->fragments * @ovcs: Overlay changeset * * Create changeset @ovcs->cset to contain the nodes and properties of the * overlay device tree fragments in @ovcs->fragments[]. If an error occurs, * any portions of the changeset that were successfully created will remain * in @ovcs->cset. * * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid overlay in @ovcs->fragments[]. */ static int build_changeset(struct overlay_changeset *ovcs) { struct fragment *fragment; int fragments_count, i, ret; /* * if there is a symbols fragment in ovcs->fragments[i] it is * the final element in the array */ if (ovcs->symbols_fragment) fragments_count = ovcs->count - 1; else fragments_count = ovcs->count; for (i = 0; i < fragments_count; i++) { fragment = &ovcs->fragments[i]; ret = build_changeset_next_level(ovcs, fragment->target, fragment->overlay); if (ret) { pr_debug("apply failed '%pOF'\n", fragment->target); return ret; } } if (ovcs->symbols_fragment) { fragment = &ovcs->fragments[ovcs->count - 1]; ret = build_changeset_symbols_node(ovcs, fragment->target, fragment->overlay); if (ret) { pr_debug("apply failed '%pOF'\n", fragment->target); return ret; } } return 0; } /* * Find the target node using a number of different strategies * in order of preference: * * 1) "target" property containing the phandle of the target * 2) "target-path" property containing the path of the target */ static struct device_node *find_target_node(struct device_node *info_node) { struct device_node *node; const char *path; u32 val; int ret; ret = of_property_read_u32(info_node, "target", &val); if (!ret) { node = of_find_node_by_phandle(val); if (!node) pr_err("find target, node: %pOF, phandle 0x%x not found\n", info_node, val); return node; } ret = of_property_read_string(info_node, "target-path", &path); if (!ret) { node = of_find_node_by_path(path); if (!node) pr_err("find target, node: %pOF, path '%s' not found\n", info_node, path); return node; } pr_err("find target, node: %pOF, no target property\n", info_node); return NULL; } /** * init_overlay_changeset() - initialize overlay changeset from overlay tree * @ovcs: Overlay changeset to build * @fdt: the FDT that was unflattened to create @tree * @tree: Contains all the overlay fragments and overlay fixup nodes * * Initialize @ovcs. Populate @ovcs->fragments with node information from * the top level of @tree. The relevant top level nodes are the fragment * nodes and the __symbols__ node. Any other top level node will be ignored. * * Returns 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error * detected in @tree, or -ENOSPC if idr_alloc() error. */ static int init_overlay_changeset(struct overlay_changeset *ovcs, const void *fdt, struct device_node *tree) { struct device_node *node, *overlay_node; struct fragment *fragment; struct fragment *fragments; int cnt, id, ret; /* * Warn for some issues. Can not return -EINVAL for these until * of_unittest_apply_overlay() is fixed to pass these checks. */ if (!of_node_check_flag(tree, OF_DYNAMIC)) pr_debug("%s() tree is not dynamic\n", __func__); if (!of_node_check_flag(tree, OF_DETACHED)) pr_debug("%s() tree is not detached\n", __func__); if (!of_node_is_root(tree)) pr_debug("%s() tree is not root\n", __func__); ovcs->overlay_tree = tree; ovcs->fdt = fdt; INIT_LIST_HEAD(&ovcs->ovcs_list); of_changeset_init(&ovcs->cset); id = idr_alloc(&ovcs_idr, ovcs, 1, 0, GFP_KERNEL); if (id <= 0) return id; cnt = 0; /* fragment nodes */ for_each_child_of_node(tree, node) { overlay_node = of_get_child_by_name(node, "__overlay__"); if (overlay_node) { cnt++; of_node_put(overlay_node); } } node = of_get_child_by_name(tree, "__symbols__"); if (node) { cnt++; of_node_put(node); } fragments = kcalloc(cnt, sizeof(*fragments), GFP_KERNEL); if (!fragments) { ret = -ENOMEM; goto err_free_idr; } cnt = 0; for_each_child_of_node(tree, node) { overlay_node = of_get_child_by_name(node, "__overlay__"); if (!overlay_node) continue; fragment = &fragments[cnt]; fragment->overlay = overlay_node; fragment->target = find_target_node(node); if (!fragment->target) { of_node_put(fragment->overlay); ret = -EINVAL; goto err_free_fragments; } cnt++; } /* * if there is a symbols fragment in ovcs->fragments[i] it is * the final element in the array */ node = of_get_child_by_name(tree, "__symbols__"); if (node) { ovcs->symbols_fragment = 1; fragment = &fragments[cnt]; fragment->overlay = node; fragment->target = of_find_node_by_path("/__symbols__"); if (!fragment->target) { pr_err("symbols in overlay, but not in live tree\n"); ret = -EINVAL; goto err_free_fragments; } cnt++; } if (!cnt) { pr_err("no fragments or symbols in overlay\n"); ret = -EINVAL; goto err_free_fragments; } ovcs->id = id; ovcs->count = cnt; ovcs->fragments = fragments; return 0; err_free_fragments: kfree(fragments); err_free_idr: idr_remove(&ovcs_idr, id); pr_err("%s() failed, ret = %d\n", __func__, ret); return ret; } static void free_overlay_changeset(struct overlay_changeset *ovcs) { int i; if (ovcs->cset.entries.next) of_changeset_destroy(&ovcs->cset); if (ovcs->id) idr_remove(&ovcs_idr, ovcs->id); for (i = 0; i < ovcs->count; i++) { of_node_put(ovcs->fragments[i].target); of_node_put(ovcs->fragments[i].overlay); } kfree(ovcs->fragments); /* * There should be no live pointers into ovcs->overlay_tree and * ovcs->fdt due to the policy that overlay notifiers are not allowed * to retain pointers into the overlay devicetree. */ kfree(ovcs->overlay_tree); kfree(ovcs->fdt); kfree(ovcs); } /* * internal documentation * * of_overlay_apply() - Create and apply an overlay changeset * @fdt: the FDT that was unflattened to create @tree * @tree: Expanded overlay device tree * @ovcs_id: Pointer to overlay changeset id * * Creates and applies an overlay changeset. * * If an error occurs in a pre-apply notifier, then no changes are made * to the device tree. * * A non-zero return value will not have created the changeset if error is from: * - parameter checks * - building the changeset * - overlay changeset pre-apply notifier * * If an error is returned by an overlay changeset pre-apply notifier * then no further overlay changeset pre-apply notifier will be called. * * A non-zero return value will have created the changeset if error is from: * - overlay changeset entry notifier * - overlay changeset post-apply notifier * * If an error is returned by an overlay changeset post-apply notifier * then no further overlay changeset post-apply notifier will be called. * * If more than one notifier returns an error, then the last notifier * error to occur is returned. * * If an error occurred while applying the overlay changeset, then an * attempt is made to revert any changes that were made to the * device tree. If there were any errors during the revert attempt * then the state of the device tree can not be determined, and any * following attempt to apply or remove an overlay changeset will be * refused. * * Returns 0 on success, or a negative error number. Overlay changeset * id is returned to *ovcs_id. */ static int of_overlay_apply(const void *fdt, struct device_node *tree, int *ovcs_id) { struct overlay_changeset *ovcs; int ret = 0, ret_revert, ret_tmp; /* * As of this point, fdt and tree belong to the overlay changeset. * overlay changeset code is responsible for freeing them. */ if (devicetree_corrupt()) { pr_err("devicetree state suspect, refuse to apply overlay\n"); kfree(fdt); kfree(tree); ret = -EBUSY; goto out; } ovcs = kzalloc(sizeof(*ovcs), GFP_KERNEL); if (!ovcs) { kfree(fdt); kfree(tree); ret = -ENOMEM; goto out; } of_overlay_mutex_lock(); mutex_lock(&of_mutex); ret = of_resolve_phandles(tree); if (ret) goto err_free_tree; ret = init_overlay_changeset(ovcs, fdt, tree); if (ret) goto err_free_tree; /* * after overlay_notify(), ovcs->overlay_tree related pointers may have * leaked to drivers, so can not kfree() tree, aka ovcs->overlay_tree; * and can not free fdt, aka ovcs->fdt */ ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY); if (ret) { pr_err("overlay changeset pre-apply notify error %d\n", ret); goto err_free_overlay_changeset; } ret = build_changeset(ovcs); if (ret) goto err_free_overlay_changeset; ret_revert = 0; ret = __of_changeset_apply_entries(&ovcs->cset, &ret_revert); if (ret) { if (ret_revert) { pr_debug("overlay changeset revert error %d\n", ret_revert); devicetree_state_flags |= DTSF_APPLY_FAIL; } goto err_free_overlay_changeset; } ret = __of_changeset_apply_notify(&ovcs->cset); if (ret) pr_err("overlay changeset entry notify error %d\n", ret); /* notify failure is not fatal, continue */ list_add_tail(&ovcs->ovcs_list, &ovcs_list); *ovcs_id = ovcs->id; ret_tmp = overlay_notify(ovcs, OF_OVERLAY_POST_APPLY); if (ret_tmp) { pr_err("overlay changeset post-apply notify error %d\n", ret_tmp); if (!ret) ret = ret_tmp; } goto out_unlock; err_free_tree: kfree(fdt); kfree(tree); err_free_overlay_changeset: free_overlay_changeset(ovcs); out_unlock: mutex_unlock(&of_mutex); of_overlay_mutex_unlock(); out: pr_debug("%s() err=%d\n", __func__, ret); return ret; } int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size, int *ovcs_id) { const void *new_fdt; int ret; u32 size; struct device_node *overlay_root; *ovcs_id = 0; ret = 0; if (overlay_fdt_size < sizeof(struct fdt_header) || fdt_check_header(overlay_fdt)) { pr_err("Invalid overlay_fdt header\n"); return -EINVAL; } size = fdt_totalsize(overlay_fdt); if (overlay_fdt_size < size) return -EINVAL; /* * Must create permanent copy of FDT because of_fdt_unflatten_tree() * will create pointers to the passed in FDT in the unflattened tree. */ new_fdt = kmemdup(overlay_fdt, size, GFP_KERNEL); if (!new_fdt) return -ENOMEM; of_fdt_unflatten_tree(new_fdt, NULL, &overlay_root); if (!overlay_root) { pr_err("unable to unflatten overlay_fdt\n"); ret = -EINVAL; goto out_free_new_fdt; } ret = of_overlay_apply(new_fdt, overlay_root, ovcs_id); if (ret < 0) { /* * new_fdt and overlay_root now belong to the overlay * changeset. * overlay changeset code is responsible for freeing them. */ goto out; } return 0; out_free_new_fdt: kfree(new_fdt); out: return ret; } EXPORT_SYMBOL_GPL(of_overlay_fdt_apply); /* * Find @np in @tree. * * Returns 1 if @np is @tree or is contained in @tree, else 0 */ static int find_node(struct device_node *tree, struct device_node *np) { struct device_node *child; if (tree == np) return 1; for_each_child_of_node(tree, child) { if (find_node(child, np)) { of_node_put(child); return 1; } } return 0; } /* * Is @remove_ce_node a child of, a parent of, or the same as any * node in an overlay changeset more topmost than @remove_ovcs? * * Returns 1 if found, else 0 */ static int node_overlaps_later_cs(struct overlay_changeset *remove_ovcs, struct device_node *remove_ce_node) { struct overlay_changeset *ovcs; struct of_changeset_entry *ce; list_for_each_entry_reverse(ovcs, &ovcs_list, ovcs_list) { if (ovcs == remove_ovcs) break; list_for_each_entry(ce, &ovcs->cset.entries, node) { if (find_node(ce->np, remove_ce_node)) { pr_err("%s: #%d overlaps with #%d @%pOF\n", __func__, remove_ovcs->id, ovcs->id, remove_ce_node); return 1; } if (find_node(remove_ce_node, ce->np)) { pr_err("%s: #%d overlaps with #%d @%pOF\n", __func__, remove_ovcs->id, ovcs->id, remove_ce_node); return 1; } } } return 0; } /* * We can safely remove the overlay only if it's the top-most one. * Newly applied overlays are inserted at the tail of the overlay list, * so a top most overlay is the one that is closest to the tail. * * The topmost check is done by exploiting this property. For each * affected device node in the log list we check if this overlay is * the one closest to the tail. If another overlay has affected this * device node and is closest to the tail, then removal is not permited. */ static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs) { struct of_changeset_entry *remove_ce; list_for_each_entry(remove_ce, &remove_ovcs->cset.entries, node) { if (node_overlaps_later_cs(remove_ovcs, remove_ce->np)) { pr_err("overlay #%d is not topmost\n", remove_ovcs->id); return 0; } } return 1; } /** * of_overlay_remove() - Revert and free an overlay changeset * @ovcs_id: Pointer to overlay changeset id * * Removes an overlay if it is permissible. @ovcs_id was previously returned * by of_overlay_fdt_apply(). * * If an error occurred while attempting to revert the overlay changeset, * then an attempt is made to re-apply any changeset entry that was * reverted. If an error occurs on re-apply then the state of the device * tree can not be determined, and any following attempt to apply or remove * an overlay changeset will be refused. * * A non-zero return value will not revert the changeset if error is from: * - parameter checks * - overlay changeset pre-remove notifier * - overlay changeset entry revert * * If an error is returned by an overlay changeset pre-remove notifier * then no further overlay changeset pre-remove notifier will be called. * * If more than one notifier returns an error, then the last notifier * error to occur is returned. * * A non-zero return value will revert the changeset if error is from: * - overlay changeset entry notifier * - overlay changeset post-remove notifier * * If an error is returned by an overlay changeset post-remove notifier * then no further overlay changeset post-remove notifier will be called. * * Returns 0 on success, or a negative error number. *ovcs_id is set to * zero after reverting the changeset, even if a subsequent error occurs. */ int of_overlay_remove(int *ovcs_id) { struct overlay_changeset *ovcs; int ret, ret_apply, ret_tmp; ret = 0; if (devicetree_corrupt()) { pr_err("suspect devicetree state, refuse to remove overlay\n"); ret = -EBUSY; goto out; } mutex_lock(&of_mutex); ovcs = idr_find(&ovcs_idr, *ovcs_id); if (!ovcs) { ret = -ENODEV; pr_err("remove: Could not find overlay #%d\n", *ovcs_id); goto out_unlock; } if (!overlay_removal_is_ok(ovcs)) { ret = -EBUSY; goto out_unlock; } ret = overlay_notify(ovcs, OF_OVERLAY_PRE_REMOVE); if (ret) { pr_err("overlay changeset pre-remove notify error %d\n", ret); goto out_unlock; } list_del(&ovcs->ovcs_list); ret_apply = 0; ret = __of_changeset_revert_entries(&ovcs->cset, &ret_apply); if (ret) { if (ret_apply) devicetree_state_flags |= DTSF_REVERT_FAIL; goto out_unlock; } ret = __of_changeset_revert_notify(&ovcs->cset); if (ret) pr_err("overlay changeset entry notify error %d\n", ret); /* notify failure is not fatal, continue */ *ovcs_id = 0; ret_tmp = overlay_notify(ovcs, OF_OVERLAY_POST_REMOVE); if (ret_tmp) { pr_err("overlay changeset post-remove notify error %d\n", ret_tmp); if (!ret) ret = ret_tmp; } free_overlay_changeset(ovcs); out_unlock: mutex_unlock(&of_mutex); out: pr_debug("%s() err=%d\n", __func__, ret); return ret; } EXPORT_SYMBOL_GPL(of_overlay_remove); /** * of_overlay_remove_all() - Reverts and frees all overlay changesets * * Removes all overlays from the system in the correct order. * * Returns 0 on success, or a negative error number */ int of_overlay_remove_all(void) { struct overlay_changeset *ovcs, *ovcs_n; int ret; /* the tail of list is guaranteed to be safe to remove */ list_for_each_entry_safe_reverse(ovcs, ovcs_n, &ovcs_list, ovcs_list) { ret = of_overlay_remove(&ovcs->id); if (ret) return ret; } return 0; } EXPORT_SYMBOL_GPL(of_overlay_remove_all);