On 04/28/2015 08:57 AM, Peter Crosthwaite wrote: > On Mon, Apr 27, 2015 at 11:46 PM, Eric Auger <eric.auger@xxxxxxxxxx> wrote: >> Hi Peter, >> >> On 04/27/2015 07:43 PM, Peter Crosthwaite wrote: >>> On Mon, Apr 27, 2015 at 8:01 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >>>> >>>> >>>> On 27/04/2015 16:56, Eric Auger wrote: >>>>> Peter, Paolo, >>>>> >>>>> After your feedbacks, I feel I need to spend some more time on the >>>>> original check() track. I would prefer not to introduce any patch that >>>>> will make issue in the future. >>>> >>>> Peter, see the other threads between me and Eric. See in particular >>>> http://lists.gnu.org/archive/html/qemu-devel/2015-04/msg02749.html >>>> starting at "The notifier actually is not even necessary" and the >>>> replies from there. >>>> >>> >>> Thanks, >>> >>> I see the problem with check. In this reply >>> >>> http://lists.gnu.org/archive/html/qemu-devel/2015-04/msg02956.html >>> >>> Eric says that the problem with the check hook is it happens before >>> the setting. I think this can be solved with a RYO link setter for >>> GPIOs. We almost have an in-tree precedent with MemoryRegion and the >>> container property (memory.c): >>> >>> 960 op = object_property_add(OBJECT(mr), "container", >>> 961 "link<" TYPE_MEMORY_REGION ">", >>> 962 memory_region_get_container, >>> 963 NULL, /* memory_region_set_container */ >>> 964 NULL, NULL, &error_abort); >>> >>> Now in reality we could have done this link normal style as it is only >>> a trivial getter, but the reason the link was done this way in the >>> first place, is because I have a follow up patch to memory.c that adds >>> a customer Link setter: >>> >>> +static void memory_region_set_container(Object *obj, Visitor *v, void *opaque, >>> + const char *name, Error **errp) >>> +{ >>> + MemoryRegion *mr = MEMORY_REGION(obj); >>> + Error *local_err = NULL; >>> + MemoryRegion *old_container = mr->container; >>> + MemoryRegion *new_container = NULL; >>> + char *path = NULL; >>> + >>> + visit_type_str(v, &path, name, &local_err); >>> + >>> + if (!local_err && strcmp(path, "") != 0) { >>> + new_container = MEMORY_REGION(object_resolve_link(obj, name, path, >>> + &local_err)); >>> + while (new_container->alias) { >>> + new_container = new_container->alias; >>> + } >>> + } >>> + >>> + if (local_err) { >>> + error_propagate(errp, local_err); >>> + return; >>> + } >>> + >>> + object_ref(OBJECT(new_container)); >>> + >>> + memory_region_transaction_begin(); >>> + memory_region_ref(mr); >>> + if (old_container) { >>> + memory_region_del_subregion(old_container, mr); >>> + } >>> + mr->container = new_container; >>> + if (new_container) { >>> + memory_region_update_container_subregions(mr); >>> + } >>> + memory_region_unref(mr); >>> + memory_region_transaction_commit(); >>> + >>> + object_unref(OBJECT(old_container)); >>> +} >>> + >>> >>> op = object_property_add(OBJECT(mr), "container", >>> "link<" TYPE_MEMORY_REGION ">", >>> memory_region_get_container, >>> - NULL, /* memory_region_set_container */ >>> + memory_region_set_container, >>> NULL, NULL, &error_abort); >>> >>> >>> The function does the normal link setting - similar to >>> object_set_link_property (not to be confused with >>> object_property_set_link!) but is surrounded by class specific side >>> effects. Specifically in this case, it does >>> memory_region_transaction_begin/ref/unref/commit etc for the MR. >>> >>> For this GPIO case, you could create a custom setter that does the >>> normal set, then calls the DeviceClass installed hook (or you can >>> install the hook to the object and init it at qdev_init_gpio_out_named >>> time as suggested in the eariler thread). The callback will happen >>> after the link is populated. >>> >>> To reduce verbosity, I suggest making object_set_link_property() a >>> visible API, then RYO link setters can call it surrounded by custom >>> behavior e.g: >>> >>> foo_object_set_bar_property(...) >>> { >>> pre_set_link_side_effects(); >>> object_set_link_property(); >>> post_set_link_side_effects(); >>> } >>> >>> object_set_link_property() would need to be coreified and wrapped to >>> remove it's awareness of LinkProperty type (as that doesn't exist in >>> RYO properties) in this case. >> >> Thank you Peter for detailing this. >> >> Yesterday I re-worked on the solution based on the check() method where >> - check would take a Object **child as a 3d parameter >> - we would assign *child before the call and in case the check fails set >> the *child back to NULL in object_set_link_property. >> > > I think this is starting to reach outside the design intent of the > check, letting it be an API that takes over the responsibility of > ->set. Ideally check should be boolean and side-effectless. I acknowledge ;-) > >> I need to do some more testing. >> >> I don't know if this solution would be acceptable too. If not I will >> implement according to your guidelines. >> > > Lets see what Paolo says before another rework. sure Thanks Eric > > Regards, > Peter > >> Best Regards >> >> Eric >>> >>> Regards, >>> Peter >>> >>>> If you have any idea, please help. >>>> >>>> Paolo >>>> >> >> _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
