// SPDX-License-Identifier: GPL-2.0 /* * Functions for working with device tree overlays * * Copyright (C) 2012 Pantelis Antoniou <[email protected]> * Copyright (C) 2012 Texas Instruments Inc. */ #define pr_fmt(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 target - info about current target node as recursing through overlay * @np: node where current level of overlay will be applied * @in_livetree: @np is a node in the live devicetree * * Used in the algorithm to create the portion of a changeset that describes * an overlay fragment, which is a devicetree subtree. Initially @np is a node * in the live devicetree where the overlay subtree is targeted to be grafted * into. When recursing to the next level of the overlay subtree, the target * also recurses to the next level of the live devicetree, as long as overlay * subtree node also exists in the live devicetree. When a node in the overlay * subtree does not exist at the same level in the live devicetree, target->np * points to a newly allocated node, and all subsequent targets in the subtree * will be newly allocated nodes. */ struct target { … }; /** * struct fragment - info about fragment nodes in overlay expanded device tree * @overlay: pointer to the __overlay__ node * @target: target of the overlay operation */ struct fragment { … }; /** * struct overlay_changeset * @id: changeset identifier * @ovcs_list: list on which we are located * @new_fdt: Memory allocated to hold unflattened aligned FDT * @overlay_mem: the memory chunk that contains @overlay_root * @overlay_root: expanded device tree that contains the fragment nodes * @notify_state: most recent notify action used on overlay * @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 { … }; /* flags are sticky - once set, do not reset */ static int devicetree_state_flags; #define DTSF_APPLY_FAIL … #define DTSF_REVERT_FAIL … /* * 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) { … } static int build_changeset_next_level(struct overlay_changeset *ovcs, struct target *target, 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) { … } void of_overlay_mutex_unlock(void) { … } 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) { … } EXPORT_SYMBOL_GPL(…); /** * of_overlay_notifier_unregister() - Unregister notifier for overlay operations * @nb: Notifier block to unregister */ int of_overlay_notifier_unregister(struct notifier_block *nb) { … } EXPORT_SYMBOL_GPL(…); static int overlay_notify(struct overlay_changeset *ovcs, enum of_overlay_notify_action action) { … } /* * The values of properties in the "/__symbols__" node are paths in * the ovcs->overlay_root. 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) { … } /** * add_changeset_property() - add @overlay_prop to overlay changeset * @ovcs: overlay changeset * @target: where @overlay_prop will be placed * @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 live devicetree, add changeset * entry to add @overlay_prop in @target, else add changeset entry to update * value of @overlay_prop. * * @target may be either in the live devicetree or in a new subtree that * is contained in the changeset. * * Some special properties are not added or updated (no error returned): * "name", "phandle", "linux,phandle". * * Properties "#address-cells" and "#size-cells" are not updated if they * are already in the live tree, but if present in the live tree, the values * in the overlay must match the values in the live tree. * * Update of property in symbols node is not allowed. * * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid @overlay. */ static int add_changeset_property(struct overlay_changeset *ovcs, struct target *target, struct property *overlay_prop, bool is_symbols_prop) { … } /** * add_changeset_node() - add @node (and children) to overlay changeset * @ovcs: overlay changeset * @target: where @node will be placed in live tree or changeset * @node: node from within overlay device tree fragment * * If @node does not already exist in @target, add changeset entry * to add @node in @target. * * If @node already exists in @target, 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. * * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid @overlay. */ static int add_changeset_node(struct overlay_changeset *ovcs, struct target *target, struct device_node *node) { … } /** * build_changeset_next_level() - add level of overlay changeset * @ovcs: overlay changeset * @target: 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. * * Return: 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 target *target, const struct device_node *overlay_node) { … } /* * Add the properties from __overlay__ node to the @ovcs->cset changeset. */ static int build_changeset_symbols_node(struct overlay_changeset *ovcs, struct target *target, const struct device_node *overlay_symbols_node) { … } static int find_dup_cset_node_entry(struct overlay_changeset *ovcs, struct of_changeset_entry *ce_1) { … } static int find_dup_cset_prop(struct overlay_changeset *ovcs, struct of_changeset_entry *ce_1) { … } /** * changeset_dup_entry_check() - check for duplicate entries * @ovcs: Overlay changeset * * Check changeset @ovcs->cset for multiple {add or delete} node entries for * the same node or duplicate {add, delete, or update} properties entries * for the same property. * * Return: 0 on success, or -EINVAL if duplicate changeset entry found. */ static int changeset_dup_entry_check(struct overlay_changeset *ovcs) { … } /** * 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. * * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if * invalid overlay in @ovcs->fragments[]. */ static int build_changeset(struct overlay_changeset *ovcs) { … } /* * 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(struct device_node *info_node, struct device_node *target_base) { … } /** * init_overlay_changeset() - initialize overlay changeset from overlay tree * @ovcs: Overlay changeset to build * @target_base: Point to the target node to apply overlay * * Initialize @ovcs. Populate @ovcs->fragments with node information from * the top level of @overlay_root. The relevant top level nodes are the * fragment nodes and the __symbols__ node. Any other top level node will * be ignored. Populate other @ovcs fields. * * Return: 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error * detected in @overlay_root. On error return, the caller of * init_overlay_changeset() must call free_overlay_changeset(). */ static int init_overlay_changeset(struct overlay_changeset *ovcs, struct device_node *target_base) { … } static void free_overlay_changeset(struct overlay_changeset *ovcs) { … } /* * internal documentation * * of_overlay_apply() - Create and apply an overlay changeset * @ovcs: overlay changeset * @base: point to the target node to apply overlay * * Creates and applies an overlay changeset. * * If an error is returned by an overlay changeset pre-apply notifier * then no further overlay changeset pre-apply notifier will be called. * * 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. On error return, * the caller of of_overlay_apply() must call free_overlay_changeset(). */ static int of_overlay_apply(struct overlay_changeset *ovcs, struct device_node *base) { … } /** * of_overlay_fdt_apply() - Create and apply an overlay changeset * @overlay_fdt: pointer to overlay FDT * @overlay_fdt_size: number of bytes in @overlay_fdt * @ret_ovcs_id: pointer for returning created changeset id * @base: pointer for the target node to apply overlay * * Creates and applies an overlay changeset. * * See of_overlay_apply() for important behavior information. * * Return: 0 on success, or a negative error number. *@ret_ovcs_id is set to * the value of overlay changeset id, which can be passed to of_overlay_remove() * to remove the overlay. * * On error return, the changeset may be partially applied. This is especially * likely if an OF_OVERLAY_POST_APPLY notifier returns an error. In this case * the caller should call of_overlay_remove() with the value in *@ret_ovcs_id. */ int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size, int *ret_ovcs_id, struct device_node *base) { … } EXPORT_SYMBOL_GPL(…); /* * 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) { … } /* * 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) { … } /* * 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 permitted. */ static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs) { … } /** * 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. * * Return: 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) { … } EXPORT_SYMBOL_GPL(…); /** * of_overlay_remove_all() - Reverts and frees all overlay changesets * * Removes all overlays from the system in the correct order. * * Return: 0 on success, or a negative error number */ int of_overlay_remove_all(void) { … } EXPORT_SYMBOL_GPL(…);
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