qdev: Replace no_user by cannot_instantiate_with_device_add_yet

In an ideal world, machines can be built by wiring devices together
with configuration, not code.  Unfortunately, that's not the world we
live in right now.  We still have quite a few devices that need to be
wired up by code.  If you try to device_add such a device, it'll fail
in sometimes mysterious ways.  If you're lucky, you get an
unmysterious immediate crash.

To protect users from such badness, DeviceClass member no_user used to
make device models unavailable with -device / device_add, but that
regressed in commit 18b6dad.  The device model is still omitted from
help, but is available anyway.

Attempts to fix the regression have been rejected with the argument
that the purpose of no_user isn't clear, and it's prone to misuse.

This commit clarifies no_user's purpose.  Anthony suggested to rename
it cannot_instantiate_with_device_add_yet_due_to_internal_bugs, which
I shorten somewhat to keep checkpatch happy.  While there, make it
bool.

Every use of cannot_instantiate_with_device_add_yet gets a FIXME
comment asking for rationale.  The next few commits will clean them
all up, either by providing a rationale, or by getting rid of the use.

With that done, the regression fix is hopefully acceptable.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel.a@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>

1 files changed, 12 insertions, 1 deletions

diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index f2043a69c2..c8945a412a 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -97,7 +97,18 @@ typedef struct DeviceClass {
     const char *fw_name;
     const char *desc;
     Property *props;
-    int no_user;
+
+    /*
+     * Shall we hide this device model from -device / device_add?
+     * All devices should support instantiation with device_add, and
+     * this flag should not exist.  But we're not there, yet.  Some
+     * devices fail to instantiate with cryptic error messages.
+     * Others instantiate, but don't work.  Exposing users to such
+     * behavior would be cruel; this flag serves to protect them.  It
+     * should never be set without a comment explaining why it is set.
+     * TODO remove once we're there
+     */
+    bool cannot_instantiate_with_device_add_yet;
 
     /* callbacks */
     void (*reset)(DeviceState *dev);