Re: [PATCH v2 3/6] qdev-monitor: add option to report GenericError from find_device_state

[Markus Armbruster <armbru@redhat.com>]

Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> writes:

> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
>  system/qdev-monitor.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/system/qdev-monitor.c b/system/qdev-monitor.c
> index 9febb743f1..cf7481e416 100644
> --- a/system/qdev-monitor.c
> +++ b/system/qdev-monitor.c
> @@ -877,13 +877,20 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp)
>      object_unref(OBJECT(dev));
>  }
>  
> -static DeviceState *find_device_state(const char *id, Error **errp)
> +/*
> + * Note that creating new APIs using error classes other than GenericError is
> + * not recommended. Set use_generic_error=true for new interfaces.
> + */
> +static DeviceState *find_device_state(const char *id, bool use_generic_error,
> +                                      Error **errp)
>  {
>      Object *obj = object_resolve_path_at(qdev_get_peripheral(), id);
>      DeviceState *dev;
>  
>      if (!obj) {
> -        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
> +        error_set(errp,
> +                  (use_generic_error ?
> +                   ERROR_CLASS_GENERIC_ERROR : ERROR_CLASS_DEVICE_NOT_FOUND),
>                    "Device '%s' not found", id);
>          return NULL;
>      }
> @@ -947,7 +954,7 @@ void qdev_unplug(DeviceState *dev, Error **errp)
>  
>  void qmp_device_del(const char *id, Error **errp)
>  {
> -    DeviceState *dev = find_device_state(id, errp);
> +    DeviceState *dev = find_device_state(id, false, errp);
>      if (dev != NULL) {
>          if (dev->pending_deleted_event &&
>              (dev->pending_deleted_expires_ms == 0 ||
> @@ -1067,7 +1074,7 @@ BlockBackend *blk_by_qdev_id(const char *id, Error **errp)
>  
>      GLOBAL_STATE_CODE();
>  
> -    dev = find_device_state(id, errp);
> +    dev = find_device_state(id, false, errp);
>      if (dev == NULL) {
>          return NULL;
>      }

I appreciate the attempt to curb the spread of DeviceNotFound errors.
Two issues:

* Copy-pasting find_device_state() with a false argument is an easy
  error to make.

* Most uses of find_device_state() are via blk_by_qdev_id() and
  qmp_get_blk().  Any new uses of qemu_get_blk() will still produce
  DeviceNotFound.

Hmm.