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of: Transactional DT support.
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Introducing DT transactional support.

A DT transaction is a method which allows one to apply changes
in the live tree, in such a way that either the full set of changes
take effect, or the state of the tree can be rolled-back to the
state it was before it was attempted. An applied transaction
can be rolled-back at any time.

Documentation is in
	Documentation/devicetree/changesets.txt

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[glikely: Removed device notifiers and reworked to be more consistent]
Signed-off-by: Grant Likely <grant.likely@linaro.org>
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@pantoniou @glikely
pantoniou authored and glikely committed Jul 23, 2014
1 parent 259092a commit 201c910
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40 changes: 40 additions & 0 deletions Documentation/devicetree/changesets.txt
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@@ -0,0 +1,40 @@
A DT changeset is a method which allows one to apply changes
in the live tree in such a way that either the full set of changes
will be applied, or none of them will be. If an error occurs partway
through applying the changeset, then the tree will be rolled back to the
previous state. A changeset can also be removed after it has been
applied.

When a changeset is applied, all of the changes get applied to the tree
at once before emitting OF_RECONFIG notifiers. This is so that the
receiver sees a complete and consistent state of the tree when it
receives the notifier.

The sequence of a changeset is as follows.

1. of_changeset_init() - initializes a changeset

2. A number of DT tree change calls, of_changeset_attach_node(),
of_changeset_detach_node(), of_changeset_add_property(),
of_changeset_remove_property, of_changeset_update_property() to prepare
a set of changes. No changes to the active tree are made at this point.
All the change operations are recorded in the of_changeset 'entries'
list.

3. mutex_lock(of_mutex) - starts a changeset; The global of_mutex
ensures there can only be one editor at a time.

4. of_changeset_apply() - Apply the changes to the tree. Either the
entire changeset will get applied, or if there is an error the tree will
be restored to the previous state

5. mutex_unlock(of_mutex) - All operations complete, release the mutex

If a successfully applied changeset needs to be removed, it can be done
with the following sequence.

1. mutex_lock(of_mutex)

2. of_changeset_revert()

3. mutex_unlock(of_mutex)
344 changes: 344 additions & 0 deletions drivers/of/dynamic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -314,3 +314,347 @@ struct device_node *__of_node_alloc(const char *full_name, gfp_t allocflags)
kfree(node);
return NULL;
}

static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
{
of_node_put(ce->np);
list_del(&ce->node);
kfree(ce);
}

#ifdef DEBUG
static void __of_changeset_entry_dump(struct of_changeset_entry *ce)
{
switch (ce->action) {
case OF_RECONFIG_ADD_PROPERTY:
pr_debug("%p: %s %s/%s\n",
ce, "ADD_PROPERTY ", ce->np->full_name,
ce->prop->name);
break;
case OF_RECONFIG_REMOVE_PROPERTY:
pr_debug("%p: %s %s/%s\n",
ce, "REMOVE_PROPERTY", ce->np->full_name,
ce->prop->name);
break;
case OF_RECONFIG_UPDATE_PROPERTY:
pr_debug("%p: %s %s/%s\n",
ce, "UPDATE_PROPERTY", ce->np->full_name,
ce->prop->name);
break;
case OF_RECONFIG_ATTACH_NODE:
pr_debug("%p: %s %s\n",
ce, "ATTACH_NODE ", ce->np->full_name);
break;
case OF_RECONFIG_DETACH_NODE:
pr_debug("%p: %s %s\n",
ce, "DETACH_NODE ", ce->np->full_name);
break;
}
}
#else
static inline void __of_changeset_entry_dump(struct of_changeset_entry *ce)
{
/* empty */
}
#endif

static void __of_changeset_entry_invert(struct of_changeset_entry *ce,
struct of_changeset_entry *rce)
{
memcpy(rce, ce, sizeof(*rce));

switch (ce->action) {
case OF_RECONFIG_ATTACH_NODE:
rce->action = OF_RECONFIG_DETACH_NODE;
break;
case OF_RECONFIG_DETACH_NODE:
rce->action = OF_RECONFIG_ATTACH_NODE;
break;
case OF_RECONFIG_ADD_PROPERTY:
rce->action = OF_RECONFIG_REMOVE_PROPERTY;
break;
case OF_RECONFIG_REMOVE_PROPERTY:
rce->action = OF_RECONFIG_ADD_PROPERTY;
break;
case OF_RECONFIG_UPDATE_PROPERTY:
rce->old_prop = ce->prop;
rce->prop = ce->old_prop;
break;
}
}

static void __of_changeset_entry_notify(struct of_changeset_entry *ce, bool revert)
{
struct of_changeset_entry ce_inverted;
int ret;

if (revert) {
__of_changeset_entry_invert(ce, &ce_inverted);
ce = &ce_inverted;
}

switch (ce->action) {
case OF_RECONFIG_ATTACH_NODE:
case OF_RECONFIG_DETACH_NODE:
ret = of_reconfig_notify(ce->action, ce->np);
break;
case OF_RECONFIG_ADD_PROPERTY:
case OF_RECONFIG_REMOVE_PROPERTY:
case OF_RECONFIG_UPDATE_PROPERTY:
ret = of_property_notify(ce->action, ce->np, ce->prop, ce->old_prop);
break;
default:
pr_err("%s: invalid devicetree changeset action: %i\n", __func__,
(int)ce->action);
return;
}

if (ret)
pr_err("%s: notifier error @%s\n", __func__, ce->np->full_name);
}

static int __of_changeset_entry_apply(struct of_changeset_entry *ce)
{
struct property *old_prop, **propp;
unsigned long flags;
int ret = 0;

__of_changeset_entry_dump(ce);

raw_spin_lock_irqsave(&devtree_lock, flags);
switch (ce->action) {
case OF_RECONFIG_ATTACH_NODE:
__of_attach_node(ce->np);
break;
case OF_RECONFIG_DETACH_NODE:
__of_detach_node(ce->np);
break;
case OF_RECONFIG_ADD_PROPERTY:
/* If the property is in deadprops then it must be removed */
for (propp = &ce->np->deadprops; *propp; propp = &(*propp)->next) {
if (*propp == ce->prop) {
*propp = ce->prop->next;
ce->prop->next = NULL;
break;
}
}

ret = __of_add_property(ce->np, ce->prop);
if (ret) {
pr_err("%s: add_property failed @%s/%s\n",
__func__, ce->np->full_name,
ce->prop->name);
break;
}
break;
case OF_RECONFIG_REMOVE_PROPERTY:
ret = __of_remove_property(ce->np, ce->prop);
if (ret) {
pr_err("%s: remove_property failed @%s/%s\n",
__func__, ce->np->full_name,
ce->prop->name);
break;
}
break;

case OF_RECONFIG_UPDATE_PROPERTY:
/* If the property is in deadprops then it must be removed */
for (propp = &ce->np->deadprops; *propp; propp = &(*propp)->next) {
if (*propp == ce->prop) {
*propp = ce->prop->next;
ce->prop->next = NULL;
break;
}
}

ret = __of_update_property(ce->np, ce->prop, &old_prop);
if (ret) {
pr_err("%s: update_property failed @%s/%s\n",
__func__, ce->np->full_name,
ce->prop->name);
break;
}
break;
default:
ret = -EINVAL;
}
raw_spin_unlock_irqrestore(&devtree_lock, flags);

if (ret)
return ret;

switch (ce->action) {
case OF_RECONFIG_ATTACH_NODE:
__of_attach_node_sysfs(ce->np);
break;
case OF_RECONFIG_DETACH_NODE:
__of_detach_node_sysfs(ce->np);
break;
case OF_RECONFIG_ADD_PROPERTY:
/* ignore duplicate names */
__of_add_property_sysfs(ce->np, ce->prop);
break;
case OF_RECONFIG_REMOVE_PROPERTY:
__of_remove_property_sysfs(ce->np, ce->prop);
break;
case OF_RECONFIG_UPDATE_PROPERTY:
__of_update_property_sysfs(ce->np, ce->prop, ce->old_prop);
break;
}

return 0;
}

static inline int __of_changeset_entry_revert(struct of_changeset_entry *ce)
{
struct of_changeset_entry ce_inverted;

__of_changeset_entry_invert(ce, &ce_inverted);
return __of_changeset_entry_apply(&ce_inverted);
}

/**
* of_changeset_init - Initialize a changeset for use
*
* @ocs: changeset pointer
*
* Initialize a changeset structure
*/
void of_changeset_init(struct of_changeset *ocs)
{
memset(ocs, 0, sizeof(*ocs));
INIT_LIST_HEAD(&ocs->entries);
}

/**
* of_changeset_destroy - Destroy a changeset
*
* @ocs: changeset pointer
*
* Destroys a changeset. Note that if a changeset is applied,
* its changes to the tree cannot be reverted.
*/
void of_changeset_destroy(struct of_changeset *ocs)
{
struct of_changeset_entry *ce, *cen;

list_for_each_entry_safe_reverse(ce, cen, &ocs->entries, node)
__of_changeset_entry_destroy(ce);
}

/**
* of_changeset_apply - Applies a changeset
*
* @ocs: changeset pointer
*
* Applies a changeset to the live tree.
* Any side-effects of live tree state changes are applied here on
* sucess, like creation/destruction of devices and side-effects
* like creation of sysfs properties and directories.
* Returns 0 on success, a negative error value in case of an error.
* On error the partially applied effects are reverted.
*/
int of_changeset_apply(struct of_changeset *ocs)
{
struct of_changeset_entry *ce;
int ret;

/* perform the rest of the work */
pr_debug("of_changeset: applying...\n");
list_for_each_entry(ce, &ocs->entries, node) {
ret = __of_changeset_entry_apply(ce);
if (ret) {
pr_err("%s: Error applying changeset (%d)\n", __func__, ret);
list_for_each_entry_continue_reverse(ce, &ocs->entries, node)
__of_changeset_entry_revert(ce);
return ret;
}
}
pr_debug("of_changeset: applied, emitting notifiers.\n");

/* drop the global lock while emitting notifiers */
mutex_unlock(&of_mutex);
list_for_each_entry(ce, &ocs->entries, node)
__of_changeset_entry_notify(ce, 0);
mutex_lock(&of_mutex);
pr_debug("of_changeset: notifiers sent.\n");

return 0;
}

/**
* of_changeset_revert - Reverts an applied changeset
*
* @ocs: changeset pointer
*
* Reverts a changeset returning the state of the tree to what it
* was before the application.
* Any side-effects like creation/destruction of devices and
* removal of sysfs properties and directories are applied.
* Returns 0 on success, a negative error value in case of an error.
*/
int of_changeset_revert(struct of_changeset *ocs)
{
struct of_changeset_entry *ce;
int ret;

pr_debug("of_changeset: reverting...\n");
list_for_each_entry_reverse(ce, &ocs->entries, node) {
ret = __of_changeset_entry_revert(ce);
if (ret) {
pr_err("%s: Error reverting changeset (%d)\n", __func__, ret);
list_for_each_entry_continue(ce, &ocs->entries, node)
__of_changeset_entry_apply(ce);
return ret;
}
}
pr_debug("of_changeset: reverted, emitting notifiers.\n");

/* drop the global lock while emitting notifiers */
mutex_unlock(&of_mutex);
list_for_each_entry_reverse(ce, &ocs->entries, node)
__of_changeset_entry_notify(ce, 1);
mutex_lock(&of_mutex);
pr_debug("of_changeset: notifiers sent.\n");

return 0;
}

/**
* of_changeset_action - Perform a changeset action
*
* @ocs: changeset pointer
* @action: action to perform
* @np: Pointer to device node
* @prop: Pointer to property
*
* On action being one of:
* + OF_RECONFIG_ATTACH_NODE
* + OF_RECONFIG_DETACH_NODE,
* + OF_RECONFIG_ADD_PROPERTY
* + OF_RECONFIG_REMOVE_PROPERTY,
* + OF_RECONFIG_UPDATE_PROPERTY
* Returns 0 on success, a negative error value in case of an error.
*/
int of_changeset_action(struct of_changeset *ocs, unsigned long action,
struct device_node *np, struct property *prop)
{
struct of_changeset_entry *ce;

ce = kzalloc(sizeof(*ce), GFP_KERNEL);
if (!ce) {
pr_err("%s: Failed to allocate\n", __func__);
return -ENOMEM;
}
/* get a reference to the node */
ce->action = action;
ce->np = of_node_get(np);
ce->prop = prop;

if (action == OF_RECONFIG_UPDATE_PROPERTY && prop)
ce->old_prop = of_find_property(np, prop->name, NULL);

/* add it to the list */
list_add_tail(&ce->node, &ocs->entries);
return 0;
}
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