[Qemu-devel] [RESEND RFC 4/6] device_tree: introduce qemu_fdt_getprop_optional

[Eric Auger <eric.auger@linaro.org>]

Current qemu_fdt_getprop exits if the property is not found. It is
sometimes needed to read an optional property, in which case we do
not wish to exit but simply returns a null value.

This is what this new qemu_fdt_getprop_optional function does.

Signed-off-by: Eric Auger <eric.auger@linaro.org>
---
 device_tree.c                | 17 +++++++++++++++++
 include/sysemu/device_tree.h |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/device_tree.c b/device_tree.c
index f184e3c..a318683 100644
--- a/device_tree.c
+++ b/device_tree.c
@@ -280,6 +280,23 @@ const void *qemu_fdt_getprop(void *fdt, const char *node_path,
     return r;
 }
 
+const void *qemu_fdt_getprop_optional(void *fdt, const char *node_path,
+                             const char *property, bool optional, int *lenp)
+{
+    int len;
+    const void *r;
+    if (!lenp) {
+        lenp = &len;
+    }
+    r = fdt_getprop(fdt, findnode_nofail(fdt, node_path), property, lenp);
+    if (!r && !optional) {
+        error_report("%s: Couldn't get %s/%s: %s", __func__,
+                     node_path, property, fdt_strerror(*lenp));
+        exit(1);
+    }
+    return r;
+}
+
 uint32_t qemu_fdt_getprop_cell(void *fdt, const char *node_path,
                                const char *property)
 {
diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
index f9e6e6e..10cbe8e 100644
--- a/include/sysemu/device_tree.h
+++ b/include/sysemu/device_tree.h
@@ -34,6 +34,8 @@ int qemu_fdt_setprop_phandle(void *fdt, const char *node_path,
                              const char *target_node_path);
 const void *qemu_fdt_getprop(void *fdt, const char *node_path,
                              const char *property, int *lenp);
+const void *qemu_fdt_getprop_optional(void *fdt, const char *node_path,
+                             const char *property, bool optional, int *lenp);
 uint32_t qemu_fdt_getprop_cell(void *fdt, const char *node_path,
                                const char *property);
 uint32_t qemu_fdt_get_phandle(void *fdt, const char *path);
-- 
1.8.3.2