[PATCH 1/3] core/device: Add function to return child node using name at substring "@"

[Athira Rajeev <atrajeev@linux.vnet.ibm.com>]

Add a function dt_find_by_name_before_addr() that returns the child node if
it matches till first occurrence at "@" of a given name, otherwise NULL.
This is helpful for cases with node name like: "name@addr". In
scenarios where nodes are added with "name@addr" format and if the
value of "addr" is not known, that node can't be matched with node
name or addr. Hence matching with substring as node name will return
the expected result. Patch adds dt_find_by_name_before_addr() function
and testcase for the same in core/test/run-device.c

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
---
Changelog:
v5 -> v6:
- Addressed review comment from Reza. Instead of using new
  variable for "node", use the node "name" as-is since the
  utility is to check the name before addr. Updated the
  test/run-device.c accordingly

v4 -> v5:
- Addressed review comment from Reza and renamed
  dt_find_by_name_substr to dt_find_by_name_before_addr

v3 -> v4:
- Addressed review comment from Mahesh and added his Reviewed-by.

v2 -> v3:
- After review comments from Mahesh, fixed the code
  to consider string upto "@" for both input node name
  as well as child node name. V2 version was comparing
  input node name and child node name upto string length
  of child name. But this will return wrong node if input
  name is larger than child name. Because it will match
  as substring for child name.
  https://lists.ozlabs.org/pipermail/skiboot/2023-January/018596.html

v1 -> v2:
- Addressed review comment from Dan to update
  the utility funtion to search and compare
  upto "@". Renamed it as dt_find_by_name_substr.

 core/device.c          | 25 +++++++++++++++++++++++++
 core/test/run-device.c | 14 ++++++++++++++
 include/device.h       |  3 +++
 3 files changed, 42 insertions(+)

diff --git a/core/device.c b/core/device.c
index 2de37c741..c22b6b3c3 100644
--- a/core/device.c
+++ b/core/device.c
@@ -395,6 +395,31 @@ struct dt_node *dt_find_by_name(struct dt_node *root, const char *name)
 }
 
 
+struct dt_node *dt_find_by_name_before_addr(struct dt_node *root, const char *name)
+{
+	struct dt_node *child, *match;
+	char *child_node = NULL;
+
+	list_for_each(&root->children, child, list) {
+		child_node = strdup(child->name);
+		if (!child_node)
+			goto err;
+		child_node = strtok(child_node, "@");
+		if (!strcmp(child_node, name)) {
+			free(child_node);
+			return child;
+		}
+
+		match = dt_find_by_name_before_addr(child, name);
+		if (match)
+			return match;
+	}
+
+	free(child_node);
+err:
+	return NULL;
+}
+
 struct dt_node *dt_new_check(struct dt_node *parent, const char *name)
 {
 	struct dt_node *node = dt_find_by_name(parent, name);
diff --git a/core/test/run-device.c b/core/test/run-device.c
index 4a12382bb..fb7a7d2c0 100644
--- a/core/test/run-device.c
+++ b/core/test/run-device.c
@@ -466,6 +466,20 @@ int main(void)
 	new_prop_ph = dt_prop_get_u32(ut2, "something");
 	assert(!(new_prop_ph == ev1_ph));
 	dt_free(subtree);
+
+	/* Test dt_find_by_name_before_addr */
+	root = dt_new_root("");
+	addr1 = dt_new_addr(root, "node", 0x1);
+	addr2 = dt_new_addr(root, "node0_1", 0x2);
+	assert(dt_find_by_name(root, "node@1") == addr1);
+	assert(dt_find_by_name(root, "node0_1@2") == addr2);
+	assert(dt_find_by_name_before_addr(root, "node") == addr1);
+	assert(dt_find_by_name_before_addr(root, "node0_") == NULL);
+	assert(dt_find_by_name_before_addr(root, "node0_1") == addr2);
+	assert(dt_find_by_name_before_addr(root, "node0") == NULL);
+	assert(dt_find_by_name_before_addr(root, "node0_") == NULL);
+	dt_free(root);
+
 	return 0;
 }
 
diff --git a/include/device.h b/include/device.h
index 93fb90ff4..f2402cc4d 100644
--- a/include/device.h
+++ b/include/device.h
@@ -184,6 +184,9 @@ struct dt_node *dt_find_by_path(struct dt_node *root, const char *path);
 /* Find a child node by name */
 struct dt_node *dt_find_by_name(struct dt_node *root, const char *name);
 
+/* Find a child node by name and substring */
+struct dt_node *dt_find_by_name_before_addr(struct dt_node *root, const char *name);
+
 /* Find a node by phandle */
 struct dt_node *dt_find_by_phandle(struct dt_node *root, u32 phandle);
 
-- 
2.31.1