[PATCH v6 1/5] hw/nvram/fw_cfg: Add the FW_CFG_DATA_GENERATOR interface

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

The FW_CFG_DATA_GENERATOR allow any object to product
blob of data consumable by the fw_cfg device.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 include/hw/nvram/fw_cfg.h | 49 +++++++++++++++++++++++++++++++++++++++
 hw/nvram/fw_cfg.c         | 30 ++++++++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index 25d9307018..74b4790fae 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -9,11 +9,40 @@
 #define TYPE_FW_CFG     "fw_cfg"
 #define TYPE_FW_CFG_IO  "fw_cfg_io"
 #define TYPE_FW_CFG_MEM "fw_cfg_mem"
+#define TYPE_FW_CFG_DATA_GENERATOR_INTERFACE "fw_cfg-data-generator"
 
 #define FW_CFG(obj)     OBJECT_CHECK(FWCfgState,    (obj), TYPE_FW_CFG)
 #define FW_CFG_IO(obj)  OBJECT_CHECK(FWCfgIoState,  (obj), TYPE_FW_CFG_IO)
 #define FW_CFG_MEM(obj) OBJECT_CHECK(FWCfgMemState, (obj), TYPE_FW_CFG_MEM)
 
+#define FW_CFG_DATA_GENERATOR_CLASS(class) \
+    OBJECT_CLASS_CHECK(FWCfgDataGeneratorClass, (class), \
+                       TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
+#define FW_CFG_DATA_GENERATOR_GET_CLASS(obj) \
+    OBJECT_GET_CLASS(FWCfgDataGeneratorClass, (obj), \
+                     TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)
+
+typedef struct FWCfgDataGeneratorClass {
+    /*< private >*/
+    InterfaceClass parent_class;
+    /*< public >*/
+
+    /**
+     * get_data:
+     * @obj: the object implementing this interface
+     *
+     * Returns: pointer to start of the generated item data
+     */
+    const void *(*get_data)(Object *obj);
+    /**
+     * get_length:
+     * @obj: the object implementing this interface
+     *
+     * Returns: the size of the generated item data in bytes
+     */
+    size_t (*get_length)(Object *obj);
+} FWCfgDataGeneratorClass;
+
 typedef struct fw_cfg_file FWCfgFile;
 
 #define FW_CFG_ORDER_OVERRIDE_VGA    70
@@ -263,6 +292,26 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char *filename,
 void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
                          size_t len);
 
+/**
+ * fw_cfg_add_from_generator:
+ * @s: fw_cfg device being modified
+ * @filename: name of new fw_cfg file item
+ * @generator_id: name of object implementing FW_CFG_DATA_GENERATOR interface
+ * @errp: pointer to a NULL initialized error object
+ *
+ * Add a new NAMED fw_cfg item with the content generated from the
+ * @generator_id object. The data referenced by the starting pointer is copied
+ * into the data structure of the fw_cfg device.
+ * The next available (unused) selector key starting at FW_CFG_FILE_FIRST
+ * will be used; also, a new entry will be added to the file directory
+ * structure residing at key value FW_CFG_FILE_DIR, containing the item name,
+ * data size, and assigned selector key value.
+ *
+ * Returns: the size of the generated item data on success, -1 otherwise.
+ */
+ssize_t fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
+                                  const char *generator_id, Error **errp);
+
 FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
                                 AddressSpace *dma_as);
 FWCfgState *fw_cfg_init_io(uint32_t iobase);
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 8dd50c2c72..e18cb074df 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -1032,6 +1032,30 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename,
     return NULL;
 }
 
+ssize_t fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
+                                  const char *generator_id, Error **errp)
+{
+    FWCfgDataGeneratorClass *k;
+    Object *o;
+    size_t sz;
+
+    o = object_resolve_path_component(object_get_objects_root(), generator_id);
+    if (!o) {
+        error_setg(errp, "Cannot find object ID %s", generator_id);
+        return -1;
+    }
+    if (!object_dynamic_cast(o, TYPE_FW_CFG_DATA_GENERATOR_INTERFACE)) {
+        error_setg(errp, "Object '%s' is not a fw_cfg-data-generator subclass",
+                         generator_id);
+        return -1;
+    }
+    k = FW_CFG_DATA_GENERATOR_GET_CLASS(o);
+    sz = k->get_length(o);
+    fw_cfg_add_file(s, filename, g_memdup(k->get_data(o), sz), sz);
+
+    return sz;
+}
+
 static void fw_cfg_machine_reset(void *opaque)
 {
     MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());
@@ -1333,12 +1357,18 @@ static const TypeInfo fw_cfg_mem_info = {
     .class_init    = fw_cfg_mem_class_init,
 };
 
+static const TypeInfo fw_cfg_data_generator_interface_info = {
+    .name = TYPE_FW_CFG_DATA_GENERATOR_INTERFACE,
+    .parent = TYPE_INTERFACE,
+    .class_size = sizeof(FWCfgDataGeneratorClass),
+};
 
 static void fw_cfg_register_types(void)
 {
     type_register_static(&fw_cfg_info);
     type_register_static(&fw_cfg_io_info);
     type_register_static(&fw_cfg_mem_info);
+    type_register_static(&fw_cfg_data_generator_interface_info);
 }
 
 type_init(fw_cfg_register_types)
-- 
2.21.3