- 根目录:
- drivers
- of
- overlay.c
/*
* 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);