monitor: introduce HumanReadableText and HMP support

This provides a foundation on which to convert simple HMP commands to
use QMP. The QMP implementation will generate formatted text targeted
for human consumption, returning it in the HumanReadableText data type.

The HMP command handler will simply print out the formatted string
within the HumanReadableText data type. Since this will be an entirely
formulaic action in the case of HMP commands taking no arguments, a
custom command handler is provided.

Thus instead of registering a 'cmd' callback for the HMP command, a
'cmd_info_hrt' callback is provided, which will simply be a pointer
to the QMP implementation.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

3 files changed, 53 insertions, 4 deletions

diff --git a/monitor/hmp.c b/monitor/hmp.c
index d50c3124e1..b20737e63c 100644
--- a/monitor/hmp.c
+++ b/monitor/hmp.c
@@ -26,6 +26,7 @@
 #include <dirent.h>
 #include "hw/qdev-core.h"
 #include "monitor-internal.h"
+#include "monitor/hmp.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qnum.h"
@@ -1061,6 +1062,31 @@ fail:
     return NULL;
 }
 
+static void hmp_info_human_readable_text(Monitor *mon,
+                                         HumanReadableText *(*handler)(Error **))
+{
+    Error *err = NULL;
+    g_autoptr(HumanReadableText) info = handler(&err);
+
+    if (hmp_handle_error(mon, err)) {
+        return;
+    }
+
+    monitor_printf(mon, "%s", info->human_readable_text);
+}
+
+static void handle_hmp_command_exec(Monitor *mon,
+                                    const HMPCommand *cmd,
+                                    QDict *qdict)
+{
+    if (cmd->cmd_info_hrt) {
+        hmp_info_human_readable_text(mon,
+                                     cmd->cmd_info_hrt);
+    } else {
+        cmd->cmd(mon, qdict);
+    }
+}
+
 typedef struct HandleHmpCommandCo {
     Monitor *mon;
     const HMPCommand *cmd;
@@ -1071,7 +1097,7 @@ typedef struct HandleHmpCommandCo {
 static void handle_hmp_command_co(void *opaque)
 {
     HandleHmpCommandCo *data = opaque;
-    data->cmd->cmd(data->mon, data->qdict);
+    handle_hmp_command_exec(data->mon, data->cmd, data->qdict);
     monitor_set_cur(qemu_coroutine_self(), NULL);
     data->done = true;
 }
@@ -1089,7 +1115,7 @@ void handle_hmp_command(MonitorHMP *mon, const char *cmdline)
         return;
     }
 
-    if (!cmd->cmd) {
+    if (!cmd->cmd && !cmd->cmd_info_hrt) {
         /* FIXME: is it useful to try autoload modules here ??? */
         monitor_printf(&mon->common, "Command \"%.*s\" is not available.\n",
                        (int)(cmdline - cmd_start), cmd_start);
@@ -1109,7 +1135,7 @@ void handle_hmp_command(MonitorHMP *mon, const char *cmdline)
     if (!cmd->coroutine) {
         /* old_mon is non-NULL when called from qmp_human_monitor_command() */
         Monitor *old_mon = monitor_set_cur(qemu_coroutine_self(), &mon->common);
-        cmd->cmd(&mon->common, qdict);
+        handle_hmp_command_exec(&mon->common, cmd, qdict);
         monitor_set_cur(qemu_coroutine_self(), old_mon);
     } else {
         HandleHmpCommandCo data = {
diff --git a/monitor/misc.c b/monitor/misc.c
index c2d227a07c..0e124044d0 100644
--- a/monitor/misc.c
+++ b/monitor/misc.c
@@ -1964,7 +1964,7 @@ void monitor_register_hmp(const char *name, bool info,
 
     while (table->name != NULL) {
         if (strcmp(table->name, name) == 0) {
-            g_assert(table->cmd == NULL);
+            g_assert(table->cmd == NULL && table->cmd_info_hrt == NULL);
             table->cmd = cmd;
             return;
         }
@@ -1973,6 +1973,22 @@ void monitor_register_hmp(const char *name, bool info,
     g_assert_not_reached();
 }
 
+void monitor_register_hmp_info_hrt(const char *name,
+                                   HumanReadableText *(*handler)(Error **errp))
+{
+    HMPCommand *table = hmp_info_cmds;
+
+    while (table->name != NULL) {
+        if (strcmp(table->name, name) == 0) {
+            g_assert(table->cmd == NULL && table->cmd_info_hrt == NULL);
+            table->cmd_info_hrt = handler;
+            return;
+        }
+        table++;
+    }
+    g_assert_not_reached();
+}
+
 void monitor_init_globals(void)
 {
     monitor_init_globals_core();
diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h
index 9c3a09cb01..3da3f86c6a 100644
--- a/monitor/monitor-internal.h
+++ b/monitor/monitor-internal.h
@@ -74,6 +74,13 @@ typedef struct HMPCommand {
     const char *help;
     const char *flags; /* p=preconfig */
     void (*cmd)(Monitor *mon, const QDict *qdict);
+    /*
+     * If implementing a command that takes no arguments and simply
+     * prints formatted data, then leave @cmd NULL, and then set
+     * @cmd_info_hrt to the corresponding QMP handler that returns
+     * the formatted text.
+     */
+    HumanReadableText *(*cmd_info_hrt)(Error **errp);
     bool coroutine;
     /*
      * @sub_table is a list of 2nd level of commands. If it does not exist,