Here we just prepare for the following patch, making possible to report
GenericError as recommended.

This patch doesn't aim to prevent further use of DeviceNotFound by
future interfaces:

 - find_device_state() is used in blk_by_qdev_id() and qmp_get_blk()
   functions, which may lead to spread of DeviceNotFound anyway
 - also, nothing prevent simply copy-pasting find_device_state() calls
   with false argument

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 6af6ef7d66..264978aa40 100644
--- a/system/qdev-monitor.c
+++ b/system/qdev-monitor.c
@@ -879,13 +879,20 @@ 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;
     }
@@ -950,7 +957,7 @@ 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 ||
@@ -1070,7 +1077,7 @@ 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;
     }
-- 
2.34.1

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

> Here we just prepare for the following patch, making possible to report
> GenericError as recommended.
>
> This patch doesn't aim to prevent further use of DeviceNotFound by
> future interfaces:
>
>  - find_device_state() is used in blk_by_qdev_id() and qmp_get_blk()
>    functions, which may lead to spread of DeviceNotFound anyway
>  - also, nothing prevent simply copy-pasting find_device_state() calls
>    with false argument

A possible way to reduce the likelihood of further spread:

1. Rename find_device_state() to find_device_state_legacy().

2. New find_device_state() that reports GenericError.

Could also be done in a follow-up.

>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

The patch does what it says on the tin, so
Reviewed-by: Markus Armbruster <armbru@redhat.com>