/* * Functions for working with device tree overlays * * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com> * Copyright (C) 2012 Texas Instruments Inc. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * version 2 as published by the Free Software Foundation. */ #undef DEBUG #include <linux/kernel.h> #include <linux/module.h> #include <linux/of.h> #include <linux/of_device.h> #include <linux/string.h> #include <linux/ctype.h> #include <linux/errno.h> #include <linux/string.h> #include <linux/slab.h> #include <linux/err.h> #include <linux/idr.h> #include "of_private.h" /** * struct of_overlay_info - Holds a single overlay info * @target: target of the overlay operation * @overlay: pointer to the overlay contents node * * Holds a single overlay state, including all the overlay logs & * records. */ struct of_overlay_info { struct device_node *target; struct device_node *overlay; }; /** * struct of_overlay - Holds a complete overlay transaction * @node: List on which we are located * @count: Count of ovinfo structures * @ovinfo_tab: Overlay info table (count sized) * @cset: Changeset to be used * * Holds a complete overlay transaction */ struct of_overlay { int id; struct list_head node; int count; struct of_overlay_info *ovinfo_tab; struct of_changeset cset; }; static int of_overlay_apply_one(struct of_overlay *ov, struct device_node *target, const struct device_node *overlay); static int of_overlay_apply_single_property(struct of_overlay *ov, struct device_node *target, struct property *prop) { struct property *propn, *tprop; /* NOTE: Multiple changes of single properties not supported */ tprop = of_find_property(target, prop->name, NULL); /* special properties are not meant to be updated (silent NOP) */ if (of_prop_cmp(prop->name, "name") == 0 || of_prop_cmp(prop->name, "phandle") == 0 || of_prop_cmp(prop->name, "linux,phandle") == 0) return 0; propn = __of_prop_dup(prop, GFP_KERNEL); if (propn == NULL) return -ENOMEM; /* not found? add */ if (tprop == NULL) return of_changeset_add_property(&ov->cset, target, propn); /* found? update */ return of_changeset_update_property(&ov->cset, target, propn); } static int of_overlay_apply_single_device_node(struct of_overlay *ov, struct device_node *target, struct device_node *child) { const char *cname; struct device_node *tchild; int ret = 0; cname = kbasename(child->full_name); if (cname == NULL) return -ENOMEM; /* NOTE: Multiple mods of created nodes not supported */ tchild = of_get_child_by_name(target, cname); if (tchild != NULL) { /* apply overlay recursively */ ret = of_overlay_apply_one(ov, tchild, child); of_node_put(tchild); } else { /* create empty tree as a target */ tchild = __of_node_dup(child, "%s/%s", target->full_name, cname); if (!tchild) return -ENOMEM; /* point to parent */ tchild->parent = target; ret = of_changeset_attach_node(&ov->cset, tchild); if (ret) return ret; ret = of_overlay_apply_one(ov, tchild, child); if (ret) return ret; } return ret; } /* * Apply a single overlay node recursively. * * Note that the in case of an error the target node is left * in a inconsistent state. Error recovery should be performed * by using the changeset. */ static int of_overlay_apply_one(struct of_overlay *ov, struct device_node *target, const struct device_node *overlay) { struct device_node *child; struct property *prop; int ret; for_each_property_of_node(overlay, prop) { ret = of_overlay_apply_single_property(ov, target, prop); if (ret) { pr_err("%s: Failed to apply prop @%s/%s\n", __func__, target->full_name, prop->name); return ret; } } for_each_child_of_node(overlay, child) { ret = of_overlay_apply_single_device_node(ov, target, child); if (ret != 0) { pr_err("%s: Failed to apply single node @%s/%s\n", __func__, target->full_name, child->name); of_node_put(child); return ret; } } return 0; } /** * of_overlay_apply() - Apply @count overlays pointed at by @ovinfo_tab * @ov: Overlay 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. */ static int of_overlay_apply(struct of_overlay *ov) { int i, err; /* first we apply the overlays atomically */ for (i = 0; i < ov->count; i++) { struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i]; err = of_overlay_apply_one(ov, ovinfo->target, ovinfo->overlay); if (err != 0) { pr_err("%s: overlay failed '%s'\n", __func__, ovinfo->target->full_name); return err; } } return 0; } /* * Find the target node using a number of different strategies * in order of preference * * "target" property containing the phandle of the target * "target-path" property containing the path of the target */ static struct device_node *find_target_node(struct device_node *info_node) { const char *path; u32 val; int ret; /* first try to go by using the target as a phandle */ ret = of_property_read_u32(info_node, "target", &val); if (ret == 0) return of_find_node_by_phandle(val); /* now try to locate by path */ ret = of_property_read_string(info_node, "target-path", &path); if (ret == 0) return of_find_node_by_path(path); pr_err("%s: Failed to find target for node %p (%s)\n", __func__, info_node, info_node->name); return NULL; } /** * of_fill_overlay_info() - Fill an overlay info structure * @ov Overlay to fill * @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. */ static int of_fill_overlay_info(struct of_overlay *ov, struct device_node *info_node, struct of_overlay_info *ovinfo) { ovinfo->overlay = of_get_child_by_name(info_node, "__overlay__"); if (ovinfo->overlay == NULL) goto err_fail; ovinfo->target = find_target_node(info_node); if (ovinfo->target == NULL) goto err_fail; return 0; err_fail: of_node_put(ovinfo->target); of_node_put(ovinfo->overlay); memset(ovinfo, 0, sizeof(*ovinfo)); return -EINVAL; } /** * of_build_overlay_info() - Build an overlay info array * @ov Overlay to build * @tree: Device node containing all the overlays * * Helper function that given a tree containing overlay information, * allocates and builds an overlay info array containing it, ready * for use using of_overlay_apply. * * Returns 0 on success with the @cntp @ovinfop pointers valid, * while on error a negative error value is returned. */ static int of_build_overlay_info(struct of_overlay *ov, struct device_node *tree) { struct device_node *node; struct of_overlay_info *ovinfo; int cnt, err; /* worst case; every child is a node */ cnt = 0; for_each_child_of_node(tree, node) cnt++; ovinfo = kcalloc(cnt, sizeof(*ovinfo), GFP_KERNEL); if (ovinfo == NULL) return -ENOMEM; cnt = 0; for_each_child_of_node(tree, node) { memset(&ovinfo[cnt], 0, sizeof(*ovinfo)); err = of_fill_overlay_info(ov, node, &ovinfo[cnt]); if (err == 0) cnt++; } /* if nothing filled, return error */ if (cnt == 0) { kfree(ovinfo); return -ENODEV; } ov->count = cnt; ov->ovinfo_tab = ovinfo; return 0; } /** * of_free_overlay_info() - Free an overlay info array * @ov Overlay to free the overlay info from * @ovinfo_tab: Array of overlay_info's to free * * Releases the memory of a previously allocated ovinfo array * by of_build_overlay_info. * Returns 0, or an error if the arguments are bogus. */ static int of_free_overlay_info(struct of_overlay *ov) { struct of_overlay_info *ovinfo; int i; /* do it in reverse */ for (i = ov->count - 1; i >= 0; i--) { ovinfo = &ov->ovinfo_tab[i]; of_node_put(ovinfo->target); of_node_put(ovinfo->overlay); } kfree(ov->ovinfo_tab); return 0; } static LIST_HEAD(ov_list); static DEFINE_IDR(ov_idr); /** * of_overlay_create() - Create and apply an overlay * @tree: Device node containing all the overlays * * Creates and applies an overlay while also keeping track * of the overlay in a list. This list can be used to prevent * illegal overlay removals. * * Returns the id of the created overlay, or a negative error number */ int of_overlay_create(struct device_node *tree) { struct of_overlay *ov; int err, id; /* allocate the overlay structure */ ov = kzalloc(sizeof(*ov), GFP_KERNEL); if (ov == NULL) return -ENOMEM; ov->id = -1; INIT_LIST_HEAD(&ov->node); of_changeset_init(&ov->cset); mutex_lock(&of_mutex); id = idr_alloc(&ov_idr, ov, 0, 0, GFP_KERNEL); if (id < 0) { pr_err("%s: idr_alloc() failed for tree@%s\n", __func__, tree->full_name); err = id; goto err_destroy_trans; } ov->id = id; /* build the overlay info structures */ err = of_build_overlay_info(ov, tree); if (err) { pr_err("%s: of_build_overlay_info() failed for tree@%s\n", __func__, tree->full_name); goto err_free_idr; } /* apply the overlay */ err = of_overlay_apply(ov); if (err) { pr_err("%s: of_overlay_apply() failed for tree@%s\n", __func__, tree->full_name); goto err_abort_trans; } /* apply the changeset */ err = __of_changeset_apply(&ov->cset); if (err) { pr_err("%s: __of_changeset_apply() failed for tree@%s\n", __func__, tree->full_name); goto err_revert_overlay; } /* add to the tail of the overlay list */ list_add_tail(&ov->node, &ov_list); mutex_unlock(&of_mutex); return id; err_revert_overlay: err_abort_trans: of_free_overlay_info(ov); err_free_idr: idr_remove(&ov_idr, ov->id); err_destroy_trans: of_changeset_destroy(&ov->cset); kfree(ov); mutex_unlock(&of_mutex); return err; } EXPORT_SYMBOL_GPL(of_overlay_create); /* check whether the given node, lies under the given tree */ static int overlay_subtree_check(struct device_node *tree, struct device_node *dn) { struct device_node *child; /* match? */ if (tree == dn) return 1; for_each_child_of_node(tree, child) { if (overlay_subtree_check(child, dn)) { of_node_put(child); return 1; } } return 0; } /* check whether this overlay is the topmost */ static int overlay_is_topmost(struct of_overlay *ov, struct device_node *dn) { struct of_overlay *ovt; struct of_changeset_entry *ce; list_for_each_entry_reverse(ovt, &ov_list, node) { /* if we hit ourselves, we're done */ if (ovt == ov) break; /* check against each subtree affected by this overlay */ list_for_each_entry(ce, &ovt->cset.entries, node) { if (overlay_subtree_check(ce->np, dn)) { pr_err("%s: #%d clashes #%d @%s\n", __func__, ov->id, ovt->id, dn->full_name); return 0; } } } /* overlay is topmost */ return 1; } /* * 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 of_overlay *ov) { struct of_changeset_entry *ce; list_for_each_entry(ce, &ov->cset.entries, node) { if (!overlay_is_topmost(ov, ce->np)) { pr_err("%s: overlay #%d is not topmost\n", __func__, ov->id); return 0; } } return 1; } /** * of_overlay_destroy() - Removes an overlay * @id: Overlay id number returned by a previous call to of_overlay_create * * Removes an overlay if it is permissible. * * Returns 0 on success, or a negative error number */ int of_overlay_destroy(int id) { struct of_overlay *ov; int err; mutex_lock(&of_mutex); ov = idr_find(&ov_idr, id); if (ov == NULL) { err = -ENODEV; pr_err("%s: Could not find overlay #%d\n", __func__, id); goto out; } /* check whether the overlay is safe to remove */ if (!overlay_removal_is_ok(ov)) { err = -EBUSY; pr_err("%s: removal check failed for overlay #%d\n", __func__, id); goto out; } list_del(&ov->node); __of_changeset_revert(&ov->cset); of_free_overlay_info(ov); idr_remove(&ov_idr, id); of_changeset_destroy(&ov->cset); kfree(ov); err = 0; out: mutex_unlock(&of_mutex); return err; } EXPORT_SYMBOL_GPL(of_overlay_destroy); /** * of_overlay_destroy_all() - Removes all overlays from the system * * Removes all overlays from the system in the correct order. * * Returns 0 on success, or a negative error number */ int of_overlay_destroy_all(void) { struct of_overlay *ov, *ovn; mutex_lock(&of_mutex); /* the tail of list is guaranteed to be safe to remove */ list_for_each_entry_safe_reverse(ov, ovn, &ov_list, node) { list_del(&ov->node); __of_changeset_revert(&ov->cset); of_free_overlay_info(ov); idr_remove(&ov_idr, ov->id); kfree(ov); } mutex_unlock(&of_mutex); return 0; } EXPORT_SYMBOL_GPL(of_overlay_destroy_all);