[v6,5/8] device_tree: qemu_fdt_getprop_cell converted to use the error API

diff --git a/device_tree.c b/device_tree.c
index 2c44a3d..c25a7b0 100644
--- a/device_tree.c
+++ b/device_tree.c
@@ -351,15 +351,22 @@  const void *qemu_fdt_getprop(void *fdt, const char *node_path,
 }
 
 uint32_t qemu_fdt_getprop_cell(void *fdt, const char *node_path,
-                               const char *property)
+                               const char *property, int *lenp, Error **errp)
 {
     int 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);
-        exit(1);
+    const uint32_t *p;
+
+    if (!lenp) {
+        lenp = &len;
+    }
+    p = qemu_fdt_getprop(fdt, node_path, property, lenp, errp);
+    if (!p) {
+        return 0;
+    } else if (*lenp != 4) {
+        error_setg(errp, "%s: %s/%s not 4 bytes long (not a cell?)",
+                   __func__, node_path, property);
+        *lenp = -EINVAL;
+        return 0;
     }
     return be32_to_cpu(*p);
 }
diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 7742dd3..65b2d9d 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -386,8 +386,10 @@  static int load_dtb(hwaddr addr, const struct arm_boot_info *binfo,
         return 0;
     }
 
-    acells = qemu_fdt_getprop_cell(fdt, "/", "#address-cells");
-    scells = qemu_fdt_getprop_cell(fdt, "/", "#size-cells");
+    acells = qemu_fdt_getprop_cell(fdt, "/", "#address-cells",
+                                   NULL, &error_fatal);
+    scells = qemu_fdt_getprop_cell(fdt, "/", "#size-cells",
+                                   NULL, &error_fatal);
     if (acells == 0 || scells == 0) {
         fprintf(stderr, "dtb file invalid (#address-cells or #size-cells 0)\n");
         goto fail;
diff --git a/hw/arm/vexpress.c b/hw/arm/vexpress.c
index 3154aea..726c4e0 100644
--- a/hw/arm/vexpress.c
+++ b/hw/arm/vexpress.c
@@ -478,8 +478,10 @@  static void vexpress_modify_dtb(const struct arm_boot_info *info, void *fdt)
     uint32_t acells, scells, intc;
     const VEDBoardInfo *daughterboard = (const VEDBoardInfo *)info;
 
-    acells = qemu_fdt_getprop_cell(fdt, "/", "#address-cells");
-    scells = qemu_fdt_getprop_cell(fdt, "/", "#size-cells");
+    acells = qemu_fdt_getprop_cell(fdt, "/", "#address-cells",
+                                   NULL, &error_fatal);
+    scells = qemu_fdt_getprop_cell(fdt, "/", "#size-cells",
+                                   NULL, &error_fatal);
     intc = find_int_controller(fdt);
     if (!intc) {
         /* Not fatal, we just won't provide virtio. This will
diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
index 48bf3b5..705650a 100644
--- a/include/sysemu/device_tree.h
+++ b/include/sysemu/device_tree.h
@@ -67,8 +67,20 @@  int qemu_fdt_setprop_phandle(void *fdt, const char *node_path,
 const void *qemu_fdt_getprop(void *fdt, const char *node_path,
                              const char *property, int *lenp,
                              Error **errp);
+/**
+ * qemu_fdt_getprop_cell: retrieve the value of a given 4 byte 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 -EINVAL if the property size is different from
+ *        4 bytes, or 4 (expected length of the property) upon success.
+ * @errp: handle to an error object
+ *
+ * returns the property value on success
+ */
 uint32_t qemu_fdt_getprop_cell(void *fdt, const char *node_path,
-                               const char *property);
+                               const char *property, int *lenp,
+                               Error **errp);
 uint32_t qemu_fdt_get_phandle(void *fdt, const char *path);
 uint32_t qemu_fdt_alloc_phandle(void *fdt);
 int qemu_fdt_nop_node(void *fdt, const char *node_path);