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of: Update comments to reflect changes and increase clarity

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Update comments to better explain what functions are doing.

Signed-off-by: Frank Rowand <frank.rowand@am.sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>
This commit is contained in:
Frank Rowand 2016-10-28 23:26:29 -07:00 committed by Rob Herring
parent ea8229b788
commit 269f1a67d0
1 changed files with 47 additions and 19 deletions
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66
drivers/of/resolver.c
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@ -50,9 +50,6 @@ static struct device_node *find_node_by_full_name(struct device_node *node,
return NULL;
}
/*
* Find live tree's maximum phandle value.
*/
static phandle live_tree_max_phandle(void)
{
struct device_node *node;
@ -71,9 +68,6 @@ static phandle live_tree_max_phandle(void)
return phandle;
}
/*
* Adjust a subtree's phandle values by a given delta.
*/
static void adjust_overlay_phandles(struct device_node *overlay,
int phandle_delta)
{
@ -81,9 +75,11 @@ static void adjust_overlay_phandles(struct device_node *overlay,
struct property *prop;
phandle phandle;
/* adjust node's phandle in node */
if (overlay->phandle != 0 && overlay->phandle != OF_PHANDLE_ILLEGAL)
overlay->phandle += phandle_delta;
/* copy adjusted phandle into *phandle properties */
for_each_property_of_node(overlay, prop) {
if (of_prop_cmp(prop->name, "phandle") &&
@ -118,6 +114,7 @@ static int update_usages_of_a_phandle_reference(struct device_node *overlay,
return -ENOMEM;
memcpy(value, prop_fixup->value, prop_fixup->length);
/* prop_fixup contains a list of tuples of path:property_name:offset */
end = value + prop_fixup->length;
for (cur = value; cur < end; cur += len + 1) {
len = strlen(cur);
@ -177,10 +174,14 @@ static int node_name_cmp(const struct device_node *dn1,
/*
* Adjust the local phandle references by the given phandle delta.
* Assumes the existances of a __local_fixups__ node at the root.
* Assumes that __of_verify_tree_phandle_references has been called.
* Does not take any devtree locks so make sure you call this on a tree
* which is at the detached state.
*
* Subtree @local_fixups, which is overlay node __local_fixups__,
* mirrors the fragment node structure at the root of the overlay.
*
* For each property in the fragments that contains a phandle reference,
* @local_fixups has a property of the same name that contains a list
* of offsets of the phandle reference(s) within the respective property
* value(s). The values at these offsets will be fixed up.
*/
static int adjust_local_phandle_references(struct device_node *local_fixups,
struct device_node *overlay, int phandle_delta)
@ -225,6 +226,13 @@ static int adjust_local_phandle_references(struct device_node *local_fixups,
}
}
/*
* These nested loops recurse down two subtrees in parallel, where the
* node names in the two subtrees match.
*
* The roots of the subtrees are the overlay's __local_fixups__ node
* and the overlay's root node.
*/
for_each_child_of_node(local_fixups, child) {
for_each_child_of_node(overlay, overlay_child)
@ -244,17 +252,37 @@ static int adjust_local_phandle_references(struct device_node *local_fixups,
}
/**
* of_resolve - Resolve the given node against the live tree.
* of_resolve_phandles - Relocate and resolve overlay against live tree
*
* @resolve: Node to resolve
* @overlay: Pointer to devicetree overlay to relocate and resolve
*
* Perform dynamic Device Tree resolution against the live tree
* to the given node to resolve. This depends on the live tree
* having a __symbols__ node, and the resolve node the __fixups__ &
* __local_fixups__ nodes (if needed).
* The result of the operation is a resolve node that it's contents
* are fit to be inserted or operate upon the live tree.
* Returns 0 on success or a negative error value on error.
* Modify (relocate) values of local phandles in @overlay to a range that
* does not conflict with the live expanded devicetree. Update references
* to the local phandles in @overlay. Update (resolve) phandle references
* in @overlay that refer to the live expanded devicetree.
*
* Phandle values in the live tree are in the range of
* 1 .. live_tree_max_phandle(). The range of phandle values in the overlay
* also begin with at 1. Adjust the phandle values in the overlay to begin
* at live_tree_max_phandle() + 1. Update references to the phandles to
* the adjusted phandle values.
*
* The name of each property in the "__fixups__" node in the overlay matches
* the name of a symbol (a label) in the live tree. The values of each
* property in the "__fixups__" node is a list of the property values in the
* overlay that need to be updated to contain the phandle reference
* corresponding to that symbol in the live tree. Update the references in
* the overlay with the phandle values in the live tree.
*
* @overlay must be detached.
*
* Resolving and applying @overlay to the live expanded devicetree must be
* protected by a mechanism to ensure that multiple overlays are processed
* in a single threaded manner so that multiple overlays will not relocate
* phandles to overlapping ranges. The mechanism to enforce this is not
* yet implemented.
*
* Return: %0 on success or a negative error value on error.
*/
int of_resolve_phandles(struct device_node *overlay)
{