[Qemu-devel] [PATCH v6 4/8] device_tree: qemu_fdt_getprop converted to use the error API

[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 patch converts qemu_fdt_getprop to accept an Error **, and existing
users are converted to pass &error_fatal. This preserves the existing
behaviour. Then to use the API with your optional semantic a null
parameter can be conveyed.

Signed-off-by: Eric Auger <eric.auger@linaro.org>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>

---
v4 -> v5:
- add Peter's R-b
- remove comment about error_fatal

v1 -> v2:
- add a doc comment in the header file

RFC -> v1:
- get rid of qemu_fdt_getprop_optional and implement Peter's suggestion
  that consists in using the error API

Signed-off-by: Eric Auger <eric.auger@linaro.org>
---
 device_tree.c                | 11 ++++++-----
 include/sysemu/device_tree.h | 13 ++++++++++++-
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/device_tree.c b/device_tree.c
index a89b838..2c44a3d 100644
--- a/device_tree.c
+++ b/device_tree.c
@@ -334,18 +334,18 @@ int qemu_fdt_setprop_string(void *fdt, const char *node_path,
 }
 
 const void *qemu_fdt_getprop(void *fdt, const char *node_path,
-                             const char *property, int *lenp)
+                             const char *property, int *lenp, Error **errp)
 {
     int len;
     const void *r;
+
     if (!lenp) {
         lenp = &len;
     }
     r = fdt_getprop(fdt, findnode_nofail(fdt, node_path), property, lenp);
     if (!r) {
-        error_report("%s: Couldn't get %s/%s: %s", __func__,
-                     node_path, property, fdt_strerror(*lenp));
-        exit(1);
+        error_setg(errp, "%s: Couldn't get %s/%s: %s", __func__,
+                  node_path, property, fdt_strerror(*lenp));
     }
     return r;
 }
@@ -354,7 +354,8 @@ uint32_t qemu_fdt_getprop_cell(void *fdt, const char *node_path,
                                const char *property)
 {
     int len;
-    const uint32_t *p = qemu_fdt_getprop(fdt, node_path, property, &len);
+    const uint32_t *p = qemu_fdt_getprop(fdt, node_path, property, &len,
+                                         &error_fatal);
     if (len != 4) {
         error_report("%s: %s/%s not 4 bytes long (not a cell?)",
                      __func__, node_path, property);
diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
index 552df21..48bf3b5 100644
--- a/include/sysemu/device_tree.h
+++ b/include/sysemu/device_tree.h
@@ -54,8 +54,19 @@ int qemu_fdt_setprop_string(void *fdt, const char *node_path,
 int qemu_fdt_setprop_phandle(void *fdt, const char *node_path,
                              const char *property,
                              const char *target_node_path);
+/**
+ * qemu_fdt_getprop: retrieve the value of a given property
+ * @fdt: pointer to the device tree blob
+ * @node_path: node path
+ * @property: name of the property to find
+ * @lenp: fdt error if any or length of the property on success
+ * @errp: handle to an error object
+ *
+ * returns a pointer to the property on success and NULL on failure
+ */
 const void *qemu_fdt_getprop(void *fdt, const char *node_path,
-                             const char *property, int *lenp);
+                             const char *property, int *lenp,
+                             Error **errp);
 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);
-- 
1.9.1