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