hw/i386: Implement fw_cfg_arch_key_name()

Implement fw_cfg_arch_key_name(), which returns the name of a
i386-specific key.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190422195020.1494-5-philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

hw/i386/Makefile.objs

@@ -3,7 +3,7 @@ obj-y += multiboot.o
 obj-y += pc.o
 obj-$(CONFIG_I440FX) += pc_piix.o
 obj-$(CONFIG_Q35) += pc_q35.o
-obj-y += pc_sysfw.o
+obj-y += fw_cfg.o pc_sysfw.o
 obj-y += x86-iommu.o
 obj-$(CONFIG_VTD) += intel_iommu.o
 obj-$(CONFIG_AMD_IOMMU) += amd_iommu.o

hw/i386/fw_cfg.c

@@ -0,0 +1,38 @@
+/*
+ * QEMU fw_cfg helpers (X86 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/i386/fw_cfg.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_ACPI_TABLES, "acpi_tables"},
+        {FW_CFG_SMBIOS_ENTRIES, "smbios_entries"},
+        {FW_CFG_IRQ0_OVERRIDE, "irq0_override"},
+        {FW_CFG_E820_TABLE, "e820_table"},
+        {FW_CFG_HPET, "hpet"},
+    };
+
+    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;
+}