BusClass currently has transitional infrastructure to support
subclasses which implement the legacy BusClass::reset method rather
than the Resettable interface.  We have now removed all the users of
BusClass::reset in the tree, so we can remove the transitional
infrastructure.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 include/hw/qdev-core.h |  2 --
 hw/core/bus.c          | 67 ------------------------------------------
 2 files changed, 69 deletions(-)

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 151d9682380..986c924fa55 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -329,8 +329,6 @@ struct BusClass {
      */
     char *(*get_fw_dev_path)(DeviceState *dev);
 
-    void (*reset)(BusState *bus);
-
     /*
      * Return whether the device can be added to @bus,
      * based on the address that was set (via device properties)
diff --git a/hw/core/bus.c b/hw/core/bus.c
index c7831b5293b..b9d89495cdf 100644
--- a/hw/core/bus.c
+++ b/hw/core/bus.c
@@ -232,57 +232,6 @@ static char *default_bus_get_fw_dev_path(DeviceState *dev)
     return g_strdup(object_get_typename(OBJECT(dev)));
 }
 
-/**
- * bus_phases_reset:
- * Transition reset method for buses to allow moving
- * smoothly from legacy reset method to multi-phases
- */
-static void bus_phases_reset(BusState *bus)
-{
-    ResettableClass *rc = RESETTABLE_GET_CLASS(bus);
-
-    if (rc->phases.enter) {
-        rc->phases.enter(OBJECT(bus), RESET_TYPE_COLD);
-    }
-    if (rc->phases.hold) {
-        rc->phases.hold(OBJECT(bus));
-    }
-    if (rc->phases.exit) {
-        rc->phases.exit(OBJECT(bus));
-    }
-}
-
-static void bus_transitional_reset(Object *obj)
-{
-    BusClass *bc = BUS_GET_CLASS(obj);
-
-    /*
-     * This will call either @bus_phases_reset (for multi-phases transitioned
-     * buses) or a bus's specific method for not-yet transitioned buses.
-     * In both case, it does not reset children.
-     */
-    if (bc->reset) {
-        bc->reset(BUS(obj));
-    }
-}
-
-/**
- * bus_get_transitional_reset:
- * check if the bus's class is ready for multi-phase
- */
-static ResettableTrFunction bus_get_transitional_reset(Object *obj)
-{
-    BusClass *dc = BUS_GET_CLASS(obj);
-    if (dc->reset != bus_phases_reset) {
-        /*
-         * dc->reset has been overridden by a subclass,
-         * the bus is not ready for multi phase yet.
-         */
-        return bus_transitional_reset;
-    }
-    return NULL;
-}
-
 static void bus_class_init(ObjectClass *class, void *data)
 {
     BusClass *bc = BUS_CLASS(class);
@@ -293,22 +242,6 @@ static void bus_class_init(ObjectClass *class, void *data)
 
     rc->get_state = bus_get_reset_state;
     rc->child_foreach = bus_reset_child_foreach;
-
-    /*
-     * @bus_phases_reset is put as the default reset method below, allowing
-     * to do the multi-phase transition from base classes to leaf classes. It
-     * allows a legacy-reset Bus class to extend a multi-phases-reset
-     * Bus class for the following reason:
-     * + If a base class B has been moved to multi-phase, then it does not
-     *   override this default reset method and may have defined phase methods.
-     * + A child class C (extending class B) which uses
-     *   bus_class_set_parent_reset() (or similar means) to override the
-     *   reset method will still work as expected. @bus_phases_reset function
-     *   will be registered as the parent reset method and effectively call
-     *   parent reset phases.
-     */
-    bc->reset = bus_phases_reset;
-    rc->get_transitional_function = bus_get_transitional_reset;
 }
 
 static void qbus_finalize(Object *obj)
-- 
2.34.1

On Fri, Jan 19, 2024 at 04:35:12PM +0000, Peter Maydell wrote:
> Date: Fri, 19 Jan 2024 16:35:12 +0000
> From: Peter Maydell <peter.maydell@linaro.org>
> Subject: [PATCH 5/5] hw/core: Remove transitional infrastructure from
>  BusClass
> X-Mailer: git-send-email 2.34.1
> 
> BusClass currently has transitional infrastructure to support
> subclasses which implement the legacy BusClass::reset method rather
> than the Resettable interface.  We have now removed all the users of
> BusClass::reset in the tree, so we can remove the transitional
> infrastructure.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/hw/qdev-core.h |  2 --
>  hw/core/bus.c          | 67 ------------------------------------------
>  2 files changed, 69 deletions(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

It seems the similar cleanup for DeviceClass needs a lot of effort.

> 
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 151d9682380..986c924fa55 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -329,8 +329,6 @@ struct BusClass {
>       */
>      char *(*get_fw_dev_path)(DeviceState *dev);
>  
> -    void (*reset)(BusState *bus);
> -
>      /*
>       * Return whether the device can be added to @bus,
>       * based on the address that was set (via device properties)
> diff --git a/hw/core/bus.c b/hw/core/bus.c
> index c7831b5293b..b9d89495cdf 100644
> --- a/hw/core/bus.c
> +++ b/hw/core/bus.c
> @@ -232,57 +232,6 @@ static char *default_bus_get_fw_dev_path(DeviceState *dev)
>      return g_strdup(object_get_typename(OBJECT(dev)));
>  }
>  
> -/**
> - * bus_phases_reset:
> - * Transition reset method for buses to allow moving
> - * smoothly from legacy reset method to multi-phases
> - */
> -static void bus_phases_reset(BusState *bus)
> -{
> -    ResettableClass *rc = RESETTABLE_GET_CLASS(bus);
> -
> -    if (rc->phases.enter) {
> -        rc->phases.enter(OBJECT(bus), RESET_TYPE_COLD);
> -    }
> -    if (rc->phases.hold) {
> -        rc->phases.hold(OBJECT(bus));
> -    }
> -    if (rc->phases.exit) {
> -        rc->phases.exit(OBJECT(bus));
> -    }
> -}
> -
> -static void bus_transitional_reset(Object *obj)
> -{
> -    BusClass *bc = BUS_GET_CLASS(obj);
> -
> -    /*
> -     * This will call either @bus_phases_reset (for multi-phases transitioned
> -     * buses) or a bus's specific method for not-yet transitioned buses.
> -     * In both case, it does not reset children.
> -     */
> -    if (bc->reset) {
> -        bc->reset(BUS(obj));
> -    }
> -}
> -
> -/**
> - * bus_get_transitional_reset:
> - * check if the bus's class is ready for multi-phase
> - */
> -static ResettableTrFunction bus_get_transitional_reset(Object *obj)
> -{
> -    BusClass *dc = BUS_GET_CLASS(obj);
> -    if (dc->reset != bus_phases_reset) {
> -        /*
> -         * dc->reset has been overridden by a subclass,
> -         * the bus is not ready for multi phase yet.
> -         */
> -        return bus_transitional_reset;
> -    }
> -    return NULL;
> -}
> -
>  static void bus_class_init(ObjectClass *class, void *data)
>  {
>      BusClass *bc = BUS_CLASS(class);
> @@ -293,22 +242,6 @@ static void bus_class_init(ObjectClass *class, void *data)
>  
>      rc->get_state = bus_get_reset_state;
>      rc->child_foreach = bus_reset_child_foreach;
> -
> -    /*
> -     * @bus_phases_reset is put as the default reset method below, allowing
> -     * to do the multi-phase transition from base classes to leaf classes. It
> -     * allows a legacy-reset Bus class to extend a multi-phases-reset
> -     * Bus class for the following reason:
> -     * + If a base class B has been moved to multi-phase, then it does not
> -     *   override this default reset method and may have defined phase methods.
> -     * + A child class C (extending class B) which uses
> -     *   bus_class_set_parent_reset() (or similar means) to override the
> -     *   reset method will still work as expected. @bus_phases_reset function
> -     *   will be registered as the parent reset method and effectively call
> -     *   parent reset phases.
> -     */
> -    bc->reset = bus_phases_reset;
> -    rc->get_transitional_function = bus_get_transitional_reset;
>  }
>  
>  static void qbus_finalize(Object *obj)
> -- 
> 2.34.1
> 
>

On Wed, 31 Jan 2024 at 03:44, Zhao Liu <zhao1.liu@intel.com> wrote:
>
> On Fri, Jan 19, 2024 at 04:35:12PM +0000, Peter Maydell wrote:
> > Date: Fri, 19 Jan 2024 16:35:12 +0000
> > From: Peter Maydell <peter.maydell@linaro.org>
> > Subject: [PATCH 5/5] hw/core: Remove transitional infrastructure from
> >  BusClass
> > X-Mailer: git-send-email 2.34.1
> >
> > BusClass currently has transitional infrastructure to support
> > subclasses which implement the legacy BusClass::reset method rather
> > than the Resettable interface.  We have now removed all the users of
> > BusClass::reset in the tree, so we can remove the transitional
> > infrastructure.
> >
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > ---
> >  include/hw/qdev-core.h |  2 --
> >  hw/core/bus.c          | 67 ------------------------------------------
> >  2 files changed, 69 deletions(-)
>
> Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
>
> It seems the similar cleanup for DeviceClass needs a lot of effort.

Yes and no. It's true that there are a lot of DeviceClass
subclasses that implement the legacy reset method still.
However, they are all "leaf" classes which provide a single
reset method, and don't need to either chain up to a parent
class reset implementation or allow a child class to
inherit from them. So they don't affect any other classes
in the system or block any other classes from being able
to use a full three-phase reset. So I'm not too worried
if we continue to have a lot of these leaf classes: the
old reset method is then just a different way of having
a device with a reset 'hold' method and no others.

I did an earlier round of refactoring back in 2022 that did
the cleanup of the non-leaf classes and the classes that
need to chain up to their parent class reset, which mostly
updated all of that kind of class to 3-phase. The one
exception is that we still have a single user of
device_class_set_parent_reset() in the s390 CPU, which
is awkward to deal with because it interacts with an
s390-specific handling of different levels of reset.

I also want to look at providing a 3-phase equivalent
of the qdev_register_reset() API at some point: that one
is definitely blocking some useful improvements, including
dealing with the vfio ordering issue, and also would let
me clean up some M-profile ARM CPU reset hacks.

thanks
-- PMM