hw/ppc: Implement fw_cfg_arch_key_name()

Implement fw_cfg_arch_key_name(), which returns the name of a
ppc-specific key.

The fw_cfg device is used by the machine using OpenBIOS:
- 40p
- mac99 (oldworld)
- g3beige (newworld)

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190422195020.1494-6-philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

hw/ppc/Makefile.objs

@@ -1,5 +1,5 @@
 # shared objects
-obj-y += ppc.o ppc_booke.o fdt.o
+obj-y += ppc.o ppc_booke.o fdt.o fw_cfg.o
 # IBM pSeries (sPAPR)
 obj-$(CONFIG_PSERIES) += spapr.o spapr_caps.o spapr_vio.o spapr_events.o
 obj-$(CONFIG_PSERIES) += spapr_hcall.o spapr_iommu.o spapr_rtas.o

hw/ppc/fw_cfg.c

@@ -0,0 +1,45 @@
+/*
+ * fw_cfg helpers (PPC specific)
+ *
+ * Copyright (c) 2019 Red Hat, Inc.
+ *
+ * Author:
+ *   Philippe Mathieu-Daudé <philmd@redhat.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "hw/ppc/ppc.h"
+#include "hw/nvram/fw_cfg.h"
+
+const char *fw_cfg_arch_key_name(uint16_t key)
+{
+    static const struct {
+        uint16_t key;
+        const char *name;
+    } fw_cfg_arch_wellknown_keys[] = {
+        {FW_CFG_PPC_WIDTH, "width"},
+        {FW_CFG_PPC_HEIGHT, "height"},
+        {FW_CFG_PPC_DEPTH, "depth"},
+        {FW_CFG_PPC_TBFREQ, "tbfreq"},
+        {FW_CFG_PPC_CLOCKFREQ, "clockfreq"},
+        {FW_CFG_PPC_IS_KVM, "is_kvm"},
+        {FW_CFG_PPC_KVM_HC, "kvm_hc"},
+        {FW_CFG_PPC_KVM_PID, "pid"},
+        {FW_CFG_PPC_NVRAM_ADDR, "nvram_addr"},
+        {FW_CFG_PPC_BUSFREQ, "busfreq"},
+        {FW_CFG_PPC_NVRAM_FLAT, "nvram_flat"},
+        {FW_CFG_PPC_VIACONFIG, "viaconfig"},
+    };
+
+    for (size_t i = 0; i < ARRAY_SIZE(fw_cfg_arch_wellknown_keys); i++) {
+        if (fw_cfg_arch_wellknown_keys[i].key == key) {
+            return fw_cfg_arch_wellknown_keys[i].name;
+        }
+    }
+    return NULL;
+}