FDT: Add a helper to get the subnode by given name

Sometimes it needs to check if there is a subnode of given node in FDT
by given name. Introduce this helper to get the subnode if it exists.

CC: Rob Herring <robh@kernel.org>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Rob Herring <robh@kernel.org>
Tested-by: Julien Grall <julien.grall@arm.com>

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 33daffc..0e02947 100644 (file)
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -744,6 +744,19 @@ int __init of_scan_flat_dt(int (*it)(unsigned long node,
 }
 
 /**
+ * of_get_flat_dt_subnode_by_name - get the subnode by given name
+ *
+ * @node: the parent node
+ * @uname: the name of subnode
+ * @return offset of the subnode, or -FDT_ERR_NOTFOUND if there is none
+ */
+
+int of_get_flat_dt_subnode_by_name(unsigned long node, const char *uname)
+{
+       return fdt_subnode_offset(initial_boot_params, node, uname);
+}
+
+/**
  * of_get_flat_dt_root - find the root node in the flat blob
  */
 unsigned long __init of_get_flat_dt_root(void)

diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index 901ec01..26c3302 100644 (file)
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -53,6 +53,8 @@ extern char __dtb_end[];
 extern int of_scan_flat_dt(int (*it)(unsigned long node, const char *uname,
                                     int depth, void *data),
                           void *data);
+extern int of_get_flat_dt_subnode_by_name(unsigned long node,
+                                         const char *uname);
 extern const void *of_get_flat_dt_prop(unsigned long node, const char *name,
                                       int *size);
 extern int of_flat_dt_is_compatible(unsigned long node, const char *name);