device_tree: add qemu_fdt_setprop_string_array helper

A string array in device tree is simply a series of \0 terminated
strings next to each other. As libfdt doesn't support that directly
we need to build it ourselves.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20210303173642.3805-4-alex.bennee@linaro.org>

include/sysemu/device_tree.h

@@ -70,6 +70,23 @@ int qemu_fdt_setprop_u64(void *fdt, const char *node_path,
                          const char *property, uint64_t val);
 int qemu_fdt_setprop_string(void *fdt, const char *node_path,
                             const char *property, const char *string);
+
+/**
+ * qemu_fdt_setprop_string_array: set a string array property
+ *
+ * @fdt: pointer to the dt blob
+ * @name: node name
+ * @prop: property array
+ * @array: pointer to an array of string pointers
+ * @len: length of array
+ *
+ * assigns a string array to a property. This function converts and
+ * array of strings to a sequential string with \0 separators before
+ * setting the property.
+ */
+int qemu_fdt_setprop_string_array(void *fdt, const char *node_path,
+                                  const char *prop, char **array, int len);
+
 int qemu_fdt_setprop_phandle(void *fdt, const char *node_path,
                              const char *property,
                              const char *target_node_path);

softmmu/device_tree.c

@@ -21,6 +21,7 @@
 #include "qemu/error-report.h"
 #include "qemu/option.h"
 #include "qemu/bswap.h"
+#include "qemu/cutils.h"
 #include "sysemu/device_tree.h"
 #include "sysemu/sysemu.h"
 #include "hw/loader.h"
@@ -397,6 +398,31 @@ int qemu_fdt_setprop_string(void *fdt, const char *node_path,
     return r;
 }
 
+/*
+ * libfdt doesn't allow us to add string arrays directly but they are
+ * test a series of null terminated strings with a length. We build
+ * the string up here so we can calculate the final length.
+ */
+int qemu_fdt_setprop_string_array(void *fdt, const char *node_path,
+                                  const char *prop, char **array, int len)
+{
+    int ret, i, total_len = 0;
+    char *str, *p;
+    for (i = 0; i < len; i++) {
+        total_len += strlen(array[i]) + 1;
+    }
+    p = str = g_malloc0(total_len);
+    for (i = 0; i < len; i++) {
+        int len = strlen(array[i]) + 1;
+        pstrcpy(p, len, array[i]);
+        p += len;
+    }
+
+    ret = qemu_fdt_setprop(fdt, node_path, prop, str, total_len);
+    g_free(str);
+    return ret;
+}
+
 const void *qemu_fdt_getprop(void *fdt, const char *node_path,
                              const char *property, int *lenp, Error **errp)
 {