Re: [PATCH v4 02/10] hw/core: create Resettable QOM interface

[Peter Maydell <peter.maydell@linaro.org>]

On Wed, 21 Aug 2019 at 17:34, Damien Hedde <damien.hedde@greensocs.com> wrote:
>
> This commit defines an interface allowing multi-phase reset. This aims
> to solve a problem of the actual single-phase reset (built in
> DeviceClass and BusClass): reset behavior is dependent on the order
> in which reset handlers are called. In particular doing external
> side-effect (like setting an qemu_irq) is problematic because receiving
> object may not be reset yet.

So, I wanted to drag up this ancient patch to ask a couple
of Resettable questions, because I'm working on adding a
new ResetType (the equivalent of SHUTDOWN_CAUSE_SNAPSHOT_LOAD).

> +/**
> + * ResetType:
> + * Types of reset.
> + *
> + * + Cold: reset resulting from a power cycle of the object.
> + *
> + * TODO: Support has to be added to handle more types. In particular,
> + * ResetState structure needs to be expanded.
> + */

Does anybody remember what this TODO comment is about? What
in particular would need to be in the ResetState struct
to allow another type to be added?

> +typedef enum ResetType {
> +    RESET_TYPE_COLD,
> +} ResetType;

> +typedef void (*ResettableInitPhase)(Object *obj, ResetType type);
> +typedef void (*ResettableHoldPhase)(Object *obj);
> +typedef void (*ResettableExitPhase)(Object *obj);

Was there a reason why we only pass the ResetType to the init
phase method, and not also to the hold and exit phases ?
Given that many devices don't need to implement init, it
seems awkward to require them to do so just to stash the
ResetType somewhere so they can look at it in the hold
or exit phase, so I was thinking about adding the argument
to the other two phase methods.

thanks
-- PMM