[Qemu-devel] 答复： Re: [PATCH v2] object: Add 'help' option for all available backends and properties

[Lin Ma]

>>> Markus Armbruster <address@hidden> 2016/9/12 星期一 下午 11:42 >>>
>Lin Ma <address@hidden> writes:
>
>> '-object help' prints available user creatable backends.
>> '-object $typename,help' prints relevant properties.
>>
>> Signed-off-by: Lin Ma <address@hidden>
>> ---
>>  include/qom/object_interfaces.h |   2 +
>>  qemu-options.hx                       |   7 ++-
>>  qom/object_interfaces.c       | 112 ++++++++++++++++++++++++++++++++++++++++
>>  vl.c                                                 |   5 ++
>>  4 files changed, 125 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 a71aaf8..fade53c 100644
>> --- a/qemu-options.hx
>> +++ b/qemu-options.hx
>> @@ -3752,7 +3752,9 @@ 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}[,@address@hidden,...]
>> @@ -3762,6 +3764,9 @@ in the order they are specified.  Note that the 'id'
>>  property must be set.  These objects are placed in the
>>  '/objects' path.
>>  
>> +Use '-object help' to print available backend types and
>> +'-object typename,help' to print relevant properties.
>> +
>
>Make that
>
>  +Use @code{-object help} to print available backend types and
>  address@hidden @var{typename},help} to print relevant properties.
>  +
>
Ok.

>>  @table @option
>>  
>>  @item -object 
>> memory-backend-file,address@hidden,address@hidden,address@hidden,address@hidden|off}
>> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
>> index bf59846..4ee8643 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 +213,117 @@ void user_creatable_del(const char *id, Error **errp)
>>        object_unparent(obj);
>>  }
>>  
>> +int user_creatable_help_func(void *opaque, QemuOpts *opts, Error **errp)
>> +{
>> +    Visitor *v;
>> +    char *type = NULL;
>> +    Error *local_err = NULL;
>> +
>
>Why this blank line?
>
I'll remove it.

>> +    int i;
>> +    char *values = NULL;
>> +    Object *obj;
>> +    ObjectPropertyInfoList *props = NULL;
>> +    ObjectProperty *prop;
>> +    ObjectPropertyIterator iter;
>> +    ObjectPropertyInfoList *start;
>> +
>> +    struct EnumProperty {
>> +        const char * const *strings;
>> +        int (*get)(Object *, Error **);
>> +        void (*set)(Object *, int, Error **);
>> +    } *enumprop;
>
>Copied from object.c.  Big no-no.  Whatever you do with this probably
>belongs into object.c instead.
>
Yes, this way is ugly.
What I want to do is parsing the enum <-> string mappings through the 
EnumProperty
to make the output more reasonable.
It should be parsed in object.c, But I can't assume the size of enum str list, 
then can't
pre-alloc it in user_creatable_help_func. So far I havn't figured out a good 
way to return
a string array that including the enum str list to user_creatable_help_func for 
printing.
May I have your suggestions?

>> +
>> +
 v = opts_visitor_new(opts);
>> +    visit_start_struct(v, NULL, NULL, 0, &local_err);
>> +    if (local_err) {
>> +        goto out;
>> +    }
>> +
>> +    visit_type_str(v, "qom-type", &type, &local_err);
>> +    if (local_err) {
>> +        goto out_visit;
>> +    }
>> +
>> +    if (type && is_help_option(type)) {
>
>I think the Options visitor is overkill.  Much simpler:
>
>          type = qemu_opt_get(opts, "qom-type");
>          if (type && is_help_option(type)) {
>
Yes, it is much simpler, I'll use this instead of visitor code.

>> +        printf("Available object backend types:\n");
>> +        GSList *list = object_class_get_list(TYPE_USER_CREATABLE, false);
>> +        while (list) {
>> +                const char *name;
>> +                name = object_class_get_name(OBJECT_CLASS(list->data));
>> +                if (strcmp(name, TYPE_USER_CREATABLE)) {
>
>Why do you need to skip TYPE_USER_CREATABLE?
>
>Hmm...
>
>    $ qemu-system-x86_64 -object user-creatable,id=foo
>    **
>    ERROR:/work/armbru/qemu/qom/object.c:361:object_initialize_with_type: 
> assertion failed (type->instance_size >= sizeof(Object)): (0 >= 40)
>    Aborted (core dumped)
>
>Should this type be abstract?
>
Yes, The object type user-creatable is abstract, But obviously it missed the 
abstract property.
I'll add it in next patch(patch 1/2), Then I dont need to skip it at here 
anymore.

>> +                        printf("%s\n", name);
>> +                }
>> +                list = list->next;
>> +        }
>
>Recommend to keep the loop control in one place:
>
>                  for (list = object_class_get_list(TYPE_USER_CREATABLE, 
> false);
>                           list;
>                           list = list->next) {
>                          ...
>                  }
>
>If you hate multi-line for (...), you can do
>
>                  GSList *head = object_class_get_list(TYPE_USER_CREATABLE, 
> false);
>
>                  for (list = head; list; list->next) {
>                          ...
>                  }
>
Will do it.

>> +        g_slist_free(list);
>> +        goto out_visit;
>> +    }
>> +
>> +    if (!type || !qemu_opt_has_help_opt(opts)) {
>> +        visit_end_struct(v, NULL);
>> +        return 0;
>> +    }
>> +
>> +    if (!object_class_by_name(type)) {
>> +        printf("invalid object type: %s\n", type);
>> +        goto out_visit;
>> +    }
>> +    obj = object_new(type);
>> +    object_property_iter_init(&iter, obj);
>> +
>> +    while ((prop = object_property_iter_next(&iter))) {
>> +        ObjectPropertyInfoList *entry = g_malloc0(sizeof(*entry));
>
>Blank line between declarations and statements, please.
>
ok.

>> +        entry->value = g_malloc0(sizeof(ObjectPropertyInfo));
>
>Either g_malloc0(sizeof(entry->value), or g_new0(ObjectPropertyInfo).
>
will use g_malloc0(sizeof(entry->value).

>> +        entry->next = props;
>> +        props = entry;
>> +        entry->value->name = g_strdup(prop->name);
>> +        i = 0;
>> +        enumprop = prop->opaque;
>> +        if (!g_str_equal(prop->type, "string") && \
>> +                !g_str_equal(prop->type, "bool") && \
>> +                !g_str_equal(prop->type, "struct tm") && \
>> +                !g_str_equal(prop->type, "int") && \
>> +                !g_str_equal(prop->type, "uint8") && \
>> +                !g_str_equal(prop->type, "uint16") && \
>> +                !g_str_equal(prop->type, "uint32") && \
>> +                !g_str_equal(prop->type, "uint64")) {
>
>Uh, what are you trying to test with this condition?  It's not obvious
>to me...
>
>> +                while (enumprop->strings[i] != NULL) {
>> +                        if (i != 0) {
>> +                                values = g_strdup_printf("%s/%s",
>> +                                                                            
>>     values, enumprop->strings[i]);
>> +                        } else {
>> +                                values = g_strdup_printf("%s", 
>> enumprop->strings[i]);
>> +                        }
>> +                        i++;
>> +                }
>> +                entry->value->type = g_strdup_printf("%s, available values: 
>> %s",
>> +                                                                            
>>             prop->type, values);
>
>Looks like this is the enum case.  But why is the condition true exactly
>for enums?
>
Yes, After filter all the other types above, I assume the result here is the 
enum case.
I knew this way does not make sense, But I havn't figured out a proper way yet 
to judge
whether the type is an enum or not.
May I have your ideas?

>> +
            } else {
>> +                entry->value->type = g_strdup(prop->type);
>> +        }
>> +    }
>
>The loop above collects properties, and ...
>
>> +
>> +    start = props;
>> +    while (props != NULL) {
>> +        ObjectPropertyInfo *value = props->value;
>> +        printf("%s (%s)\n", value->name, value->type);
>> +        props = props->next;
>> +    }
>> +    qapi_free_ObjectPropertyInfoList(start);
>
>... this loop prints them.  Have you considered fusing the two loops?
>
I agreed. will merge the two loops.

>> +
>> +out_visit:
>> +    visit_end_struct(v, NULL);
>> +
>> +out:
>> +    g_free(values);
>> +    g_free(type);
>> +    object_unref(obj);
>> +    if (local_err) {
>> +        error_report_err(local_err);
>> +    }
>> +    return 1;
>> +}
>> +
>>  static void register_types(void)
>>  {
>>        static const TypeInfo uc_interface_info = {
>> diff --git a/vl.c b/vl.c
>> index ee557a1..a2230c8 100644
>> --- a/vl.c
>> +++ b/vl.c
>> @@ -4251,6 +4251,11 @@ int main(int argc, char **argv, char **envp)
>>        page_size_init();
>>        socket_init();
>>  
>> +    if (qemu_opts_foreach(qemu_find_opts("object"), 
>> user_creatable_help_func,
>> +                                              NULL, NULL)) {
>> +        exit(1);
>> +    }
>> +
>
>I think this should be done as early as possible.  However, we already
>do -device help nearby.  Not fair to ask you to clean up this mess.
>
How about move it to here?
         object_property_add_child(object_get_root(), "machine",
                                                           
OBJECT(current_machine), &error_abort);
+
+    if (qemu_opts_foreach(qemu_find_opts("object"), user_creatable_help_func,
+                                                 NULL, NULL)) {
+           exit(1);
+    }
+
         cpu_exec_init_all();

>>        if (qemu_opts_foreach(qemu_find_opts("object"),
>>                                                  
>> user_creatable_add_opts_foreach,
>>                                                  object_create_initial, 
>> NULL)) {

Thank you for reviewing the code.
Lin