Re: [Qemu-devel] [PATCH v4 5/5] object: Add 'help' option for all available backends and properties

[Markus Armbruster]

Lin Ma  writes:

> '-object help' prints available user creatable backends.
> '-object $typename,help' prints relevant properties.
>
> Signed-off-by: Lin Ma 
> ---
>  include/qom/object_interfaces.h |  2 ++
>  qemu-options.hx |  7 +-
>  qom/object_interfaces.c | 55 
> +
>  vl.c|  5 
>  4 files changed, 68 insertions(+), 1 deletion(-)
>
> diff --git a/include/qom/object_interfaces.h b/include/qom/object_interfaces.h
> index 8b17f4d..197cd5f 100644
> --- a/include/qom/object_interfaces.h
> +++ b/include/qom/object_interfaces.h
> @@ -165,4 +165,6 @@ int user_creatable_add_opts_foreach(void *opaque,
>   */
>  void user_creatable_del(const char *id, Error **errp);
>  
> +int user_creatable_help_func(void *opaque, QemuOpts *opts, Error **errp);
> +

Ugly interface: two arguments that aren't used, one of them void *.
Suggest to follow the device help example: do a non-ugly interface here,
and an ugly, but static wrapper in vl.c

>  #endif
> diff --git a/qemu-options.hx b/qemu-options.hx
> index b1fbdb0..b9573ce 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3761,7 +3761,9 @@ DEF("object", HAS_ARG, QEMU_OPTION_object,
>  "create a new object of type TYPENAME setting 
> properties\n"
>  "in the order they are specified.  Note that the 'id'\n"
>  "property must be set.  These objects are placed in 
> the\n"
> -"'/objects' path.\n",
> +"'/objects' path.\n"
> +"Use '-object help' to print available backend types 
> and\n"
> +"'-object typename,help' to print relevant 
> properties.\n",

The existing text talks about "object of type TYPENAME".  The new text
suddenly talks about "backend types".  Switching terminology is not a
good idea.  Call them "object types".

For comparison, here's the text we use for -device:

use '-device help' to print all possible drivers
use '-device driver,help' to print all possible properties

Let's make this one similar:

use '-object help' to print all possible object types
use '-object driver,help' to print all possible properties

>  QEMU_ARCH_ALL)
>  STEXI
>  @item -object @var{typename}[,@var{prop1}=@var{value1},...]
> @@ -3771,6 +3773,9 @@ in the order they are specified.  Note that the 'id'
>  property must be set.  These objects are placed in the
>  '/objects' path.
>  
> +Use @code{-object help} to print available backend types and
> +@code{-object @var{typename},help} to print relevant properties.
> +

-device's text:

To get help on possible drivers and properties, use @code{-device
help} and @code{-device @var{driver},help}.

Suggest:

To get help on possible object types and properties, use @code{-object
help} and @code{-object @var{type},help}.

>  @table @option
>  
>  @item -object 
> memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off}
> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
> index bf59846..da8be39 100644
> --- a/qom/object_interfaces.c
> +++ b/qom/object_interfaces.c
> @@ -5,6 +5,7 @@
>  #include "qapi-visit.h"
>  #include "qapi/qmp-output-visitor.h"
>  #include "qapi/opts-visitor.h"
> +#include "qemu/help_option.h"
>  
>  void user_creatable_complete(Object *obj, Error **errp)
>  {
> @@ -212,6 +213,60 @@ void user_creatable_del(const char *id, Error **errp)
>  object_unparent(obj);
>  }
>  
> +int user_creatable_help_func(void *opaque, QemuOpts *opts, Error **errp)
> +{
> +const char *type = NULL;
> +Object *obj = NULL;
> +ObjectClass *klass;
> +ObjectProperty *prop;
> +ObjectPropertyIterator iter;
> +
> +type = qemu_opt_get(opts, "qom-type");
> +if (type && is_help_option(type)) {
> +GSList *list;
> +printf("Available object backend types:\n");

Wrong when running for an HMP monitor command, e.g. "object_add help".
Use error_printf().  That's only slightly wrong in that it prints to
stderr instead of stdout running for the command line.

> +for (list = object_class_get_list(TYPE_USER_CREATABLE, false);  \
> +list;   \
> +list = list->next) {

Superfluous line continuations.  Simply write

   for (list = object_class_get_list(TYPE_USER_CREATABLE, false);
list;
list = list->next) {

Alternatively,

   list = object_class_get_list(TYPE_USER_CREATABLE, false);
   for (elt = list; elt; elt = elt->next) {

> +const char *name;
> +name = object_class_get_name(OBJECT_CLASS(list->data));
> +if (strcmp(name, TYPE_USER_CREATABLE)) {
> +printf("%s\n", name);

error_printf()

> +}
> +}
> +

[Qemu-devel] [PATCH v4 5/5] object: Add 'help' option for all available backends and properties

[Lin Ma]

'-object help' prints available user creatable backends.
'-object $typename,help' prints relevant properties.

Signed-off-by: Lin Ma 
---
 include/qom/object_interfaces.h |  2 ++
 qemu-options.hx |  7 +-
 qom/object_interfaces.c | 55 +
 vl.c|  5 
 4 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/include/qom/object_interfaces.h b/include/qom/object_interfaces.h
index 8b17f4d..197cd5f 100644
--- a/include/qom/object_interfaces.h
+++ b/include/qom/object_interfaces.h
@@ -165,4 +165,6 @@ int user_creatable_add_opts_foreach(void *opaque,
  */
 void user_creatable_del(const char *id, Error **errp);
 
+int user_creatable_help_func(void *opaque, QemuOpts *opts, Error **errp);
+
 #endif
diff --git a/qemu-options.hx b/qemu-options.hx
index b1fbdb0..b9573ce 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3761,7 +3761,9 @@ DEF("object", HAS_ARG, QEMU_OPTION_object,
 "create a new object of type TYPENAME setting properties\n"
 "in the order they are specified.  Note that the 'id'\n"
 "property must be set.  These objects are placed in the\n"
-"'/objects' path.\n",
+"'/objects' path.\n"
+"Use '-object help' to print available backend types and\n"
+"'-object typename,help' to print relevant properties.\n",
 QEMU_ARCH_ALL)
 STEXI
 @item -object @var{typename}[,@var{prop1}=@var{value1},...]
@@ -3771,6 +3773,9 @@ in the order they are specified.  Note that the 'id'
 property must be set.  These objects are placed in the
 '/objects' path.
 
+Use @code{-object help} to print available backend types and
+@code{-object @var{typename},help} to print relevant properties.
+
 @table @option
 
 @item -object 
memory-backend-file,id=@var{id},size=@var{size},mem-path=@var{dir},share=@var{on|off}
diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
index bf59846..da8be39 100644
--- a/qom/object_interfaces.c
+++ b/qom/object_interfaces.c
@@ -5,6 +5,7 @@
 #include "qapi-visit.h"
 #include "qapi/qmp-output-visitor.h"
 #include "qapi/opts-visitor.h"
+#include "qemu/help_option.h"
 
 void user_creatable_complete(Object *obj, Error **errp)
 {
@@ -212,6 +213,60 @@ void user_creatable_del(const char *id, Error **errp)
 object_unparent(obj);
 }
 
+int user_creatable_help_func(void *opaque, QemuOpts *opts, Error **errp)
+{
+const char *type = NULL;
+Object *obj = NULL;
+ObjectClass *klass;
+ObjectProperty *prop;
+ObjectPropertyIterator iter;
+
+type = qemu_opt_get(opts, "qom-type");
+if (type && is_help_option(type)) {
+GSList *list;
+printf("Available object backend types:\n");
+for (list = object_class_get_list(TYPE_USER_CREATABLE, false);  \
+list;   \
+list = list->next) {
+const char *name;
+name = object_class_get_name(OBJECT_CLASS(list->data));
+if (strcmp(name, TYPE_USER_CREATABLE)) {
+printf("%s\n", name);
+}
+}
+g_slist_free(list);
+goto out;
+}
+
+if (!type || !qemu_opt_has_help_opt(opts)) {
+return 0;
+}
+
+klass = object_class_by_name(type);
+if (!klass) {
+printf("invalid object type: %s\n", type);
+goto out;
+}
+if (object_class_is_abstract(klass)) {
+printf("object type '%s' is abstract\n", type);
+goto out;
+}
+obj = object_new(type);
+object_property_iter_init(, obj);
+
+while ((prop = object_property_iter_next())) {
+if (prop->description) {
+printf("%s (%s, %s)\n", prop->name, prop->type, prop->description);
+} else {
+printf("%s (%s)\n", prop->name, prop->type);
+}
+}
+
+out:
+object_unref(obj);
+return 1;
+}
+
 static void register_types(void)
 {
 static const TypeInfo uc_interface_info = {
diff --git a/vl.c b/vl.c
index ebd47af..1456eca 100644
--- a/vl.c
+++ b/vl.c
@@ -4100,6 +4100,11 @@ int main(int argc, char **argv, char **envp)
 exit(0);
 }
 
+if (qemu_opts_foreach(qemu_find_opts("object"), user_creatable_help_func,
+  NULL, NULL)) {
+exit(1);
+}
+
 if (!trace_init_backends()) {
 exit(1);
 }
-- 
2.9.2