From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57870) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wwu2O-0001QS-Oc for qemu-devel@nongnu.org; Tue, 17 Jun 2014 10:07:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wwu2I-0002XG-P1 for qemu-devel@nongnu.org; Tue, 17 Jun 2014 10:07:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25089) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wwu2I-0002X5-H4 for qemu-devel@nongnu.org; Tue, 17 Jun 2014 10:06:54 -0400 Message-ID: <53A04B79.808@redhat.com> Date: Tue, 17 Jun 2014 16:06:49 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1402505369-12526-1-git-send-email-pbonzini@redhat.com> <1402505369-12526-5-git-send-email-pbonzini@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/5] qom: allow creating an alias of an object List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Crosthwaite Cc: Marcelo Tosatti , "qemu-devel@nongnu.org Developers" , Stefan Hajnoczi , =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= Il 17/06/2014 15:55, Peter Crosthwaite ha scritto: > On Thu, Jun 12, 2014 at 2:49 AM, Paolo Bonzini wrote: >> Add a shorthand for creating an alias of a child<> property. If you >> pass a NULL target_name to object_property_add_alias, the function >> will look up the child property that leads to target_obj, and create >> an alias for that property. >> >> This can be useful when an object wants to add a link to itself >> at a well-known location. For example, a real-time clock device might >> add a link to itself at "/machine/rtc". Such well-known locations can >> then expose a standard set of properties that can be accessed via the >> "qom-get" and "qom-set" commands. >> >> Signed-off-by: Paolo Bonzini >> --- >> include/qom/object.h | 10 +++++++--- >> qom/object.c | 16 +++++++++++++--- >> 2 files changed, 20 insertions(+), 6 deletions(-) >> >> diff --git a/include/qom/object.h b/include/qom/object.h >> index 9c4a5a4..9cd0ffa 100644 >> --- a/include/qom/object.h >> +++ b/include/qom/object.h >> @@ -1256,11 +1256,15 @@ void object_property_add_uint64_ptr(Object *obj, const char *name, >> * @obj: the object to add a property to >> * @name: the name of the property >> * @target_obj: the object to forward property access to >> - * @target_name: the name of the property on the forwarded object >> + * @target_name: the name of the property on the forwarded object, or >> + * #NULL to make an object alias. >> * @errp: if an error occurs, a pointer to an area to store the error >> * >> - * Add an alias for a property on an object. This function will add a property >> - * of the same type as the forwarded property. >> + * Add an alias property on an object. This function will add a property >> + * of the same type as the forwarded property or, if @target_name is #NULL, >> + * a link property that always resolves to @target_obj. In fact, the case >> + * of a #NULL @target_obj actually creates an alias property that targets >> + * @target_obj's own child property. >> * >> * The caller must ensure that @target_obj stays alive as long as >> * this property exists. In the case of a child object or an alias on the same >> diff --git a/qom/object.c b/qom/object.c >> index ddf781e..1e8e6af 100644 >> --- a/qom/object.c >> +++ b/qom/object.c >> @@ -1535,7 +1535,7 @@ void object_property_add_uint64_ptr(Object *obj, const char *name, >> typedef struct >> { >> Object *target_obj; >> - const char *target_name; >> + char *target_name; >> } AliasProperty; >> >> static void property_get_alias(Object *obj, struct Visitor *v, void *opaque, >> @@ -1566,6 +1566,7 @@ static void property_release_alias(Object *obj, const char *name, void *opaque) >> { >> AliasProperty *prop = opaque; >> >> + g_free(prop->target_name); >> g_free(prop); >> } >> >> @@ -1576,9 +1577,18 @@ void object_property_add_alias(Object *obj, const char *name, >> AliasProperty *prop; >> ObjectProperty *target_prop; >> gchar *prop_type; >> + gchar *the_target_name; >> >> - target_prop = object_property_find(target_obj, target_name, errp); >> + if (!target_name) { >> + the_target_name = object_get_canonical_path_component(target_obj); >> + target_obj = target_obj->parent; > > This semantic seems a little tricky. It also get the target's > canon-parent entangled in the process whereas your original > object_property_add_alias is more self contained: > > http://lists.gnu.org/archive/html/qemu-devel/2014-06/msg01203.html > > For instance - could you unparent then reparent an object and have > it's aliases survive? I think the best implementation is to simply > place your original alias logic here under if (!target_name) and > return. Ok, so that would mean special casing target_prop == NULL. Paolo