[RFC PATCH v2 02/23] hw/core/qdev: Add qdev_warn_deprecated_function_used() helper

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

When built with --enable-qdev-deprecation-warning, calling
qdev_warn_deprecated_function_used() will emit a warning such:

  $ qemu-system-arm -M verdex ...
  qemu-system-arm: warning: use of deprecated non-qdev/non-qom code in pxa2xx_lcdc_init()
  qemu-system-arm: warning: use of deprecated non-qdev/non-qom code in pxa2xx_i2s_init()
  qemu-system-arm: warning: use of deprecated non-qdev/non-qom code in pxa27x_keypad_init()

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
I'd rather use --enable-qdev-debug suggested here:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg719802.html
---
 configure                    |  8 ++++++++
 include/hw/qdev-deprecated.h | 26 ++++++++++++++++++++++++++
 hw/core/qdev.c               |  8 ++++++++
 3 files changed, 42 insertions(+)
 create mode 100644 include/hw/qdev-deprecated.h

diff --git a/configure b/configure
index 8a65240d4a..aac3dc0767 100755
--- a/configure
+++ b/configure
@@ -441,6 +441,7 @@ edk2_blobs="no"
 pkgversion=""
 pie=""
 qom_cast_debug="yes"
+qdev_deprecation_warning="no"
 trace_backends="log"
 trace_file="trace"
 spice=""
@@ -1124,6 +1125,8 @@ for opt do
   ;;
   --enable-qom-cast-debug) qom_cast_debug="yes"
   ;;
+  --enable-qdev-deprecation-warning) qdev_deprecation_warning="yes"
+  ;;
   --disable-virtfs) virtfs="no"
   ;;
   --enable-virtfs) virtfs="yes"
@@ -1915,6 +1918,7 @@ disabled with --disable-FEATURE, default is enabled if available:
   virglrenderer   virgl rendering support
   xfsctl          xfsctl support
   qom-cast-debug  cast debugging support
+  qdev-deprecation-warning display qdev deprecation warnings
   tools           build qemu-io, qemu-nbd and qemu-img tools
   vxhs            Veritas HyperScale vDisk backend support
   bochs           bochs image format support
@@ -6966,6 +6970,7 @@ echo "gcov enabled      $gcov"
 echo "TPM support       $tpm"
 echo "libssh support    $libssh"
 echo "QOM debugging     $qom_cast_debug"
+echo "QDEV deprecation warnings $qdev_deprecation_warning"
 echo "Live block migration $live_block_migration"
 echo "lzo support       $lzo"
 echo "snappy support    $snappy"
@@ -7594,6 +7599,9 @@ fi
 if test "$qom_cast_debug" = "yes" ; then
   echo "CONFIG_QOM_CAST_DEBUG=y" >> $config_host_mak
 fi
+if test "$qdev_deprecation_warning" = "yes" ; then
+  echo "CONFIG_QDEV_DEPRECATION_WARNING=y" >> $config_host_mak
+fi
 if test "$rbd" = "yes" ; then
   echo "CONFIG_RBD=m" >> $config_host_mak
   echo "RBD_CFLAGS=$rbd_cflags" >> $config_host_mak
diff --git a/include/hw/qdev-deprecated.h b/include/hw/qdev-deprecated.h
new file mode 100644
index 0000000000..b815f62dae
--- /dev/null
+++ b/include/hw/qdev-deprecated.h
@@ -0,0 +1,26 @@
+/*
+ * QEMU QOM qdev deprecation helpers
+ *
+ * Copyright (c) 2020 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.
+ */
+#ifndef HW_QDEV_DEPRECATED_H
+#define HW_QDEV_DEPRECATED_H
+
+/**
+ * qdev_warn_deprecated_function_used:
+ *
+ * Display a warning that deprecated code is used.
+ */
+#define qdev_warn_deprecated_function_used() \
+    qdev_warn_deprecated_function(__func__)
+void qdev_warn_deprecated_function(const char *function);
+
+#endif
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 2131c7f951..1134f46631 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -35,6 +35,7 @@
 #include "hw/hotplug.h"
 #include "hw/irq.h"
 #include "hw/qdev-properties.h"
+#include "hw/qdev-deprecated.h"
 #include "hw/boards.h"
 #include "hw/sysbus.h"
 #include "hw/qdev-clock.h"
@@ -838,6 +839,13 @@ void qdev_alias_all_properties(DeviceState *target, Object *source)
     } while (class != object_class_by_name(TYPE_DEVICE));
 }
 
+void qdev_warn_deprecated_function(const char *function)
+{
+#ifdef CONFIG_QDEV_DEPRECATION_WARNING
+    warn_report("use of deprecated non-qdev/non-qom code in %s()", function);
+#endif
+}
+
 static bool device_get_realized(Object *obj, Error **errp)
 {
     DeviceState *dev = DEVICE(obj);
-- 
2.21.3