sysbus: Make devices picking up backends unavailable with -device

Device models aren't supposed to go on fishing expeditions for
backends.  They should expose suitable properties for the user to set.
For onboard devices, board code sets them.

A number of sysbus devices pick up block backends in their init() /
instance_init() methods with drive_get_next() instead: sl-nand,
milkymist-memcard, pl181, generic-sdhci.

Likewise, a number of sysbus devices pick up character backends in
their init() / realize() methods with qemu_char_get_next_serial():
cadence_uart, digic-uart, etraxfs,serial, lm32-juart, lm32-uart,
milkymist-uart, pl011, stm32f2xx-usart, xlnx.xps-uartlite.

All these mistakes are already marked FIXME.  See the commit that
added these FIXMEs for a more detailed explanation of what's wrong.

Fortunately, only machines ppce500 and pseries-* support -device with
sysbus devices, and none of the devices above is supported with these
machines.

Set cannot_instantiate_with_device_add_yet to preserve our luck.

Cc: Andrzej Zaborowski <balrogg@gmail.com>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: Antony Pavlov <antonynpavlov@gmail.com>
Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Cc: Michael Walle <michael@walle.cc>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/hw/char/digic-uart.c b/hw/char/digic-uart.c
index f272491..6d44576 100644
--- a/hw/char/digic-uart.c
+++ b/hw/char/digic-uart.c
@@ -177,6 +177,8 @@ static void digic_uart_class_init(ObjectClass *klass, void *data)
     dc->realize = digic_uart_realize;
     dc->reset = digic_uart_reset;
     dc->vmsd = &vmstate_digic_uart;
+    /* Reason: realize() method uses qemu_char_get_next_serial() */
+    dc->cannot_instantiate_with_device_add_yet = true;
 }
 
 static const TypeInfo digic_uart_info = {