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[PATCH 1/4] qdev: Support marking individual buses as 'full'
From: |
Peter Maydell |
Subject: |
[PATCH 1/4] qdev: Support marking individual buses as 'full' |
Date: |
Fri, 3 Sep 2021 16:14:32 +0100 |
By default, QEMU will allow devices to be plugged into a bus up to
the bus class's device count limit. If the user creates a device on
the command line or via the monitor and doesn't explicitly specify
the bus to plug it in, QEMU will plug it into the first non-full bus
that it finds.
This is fine in most cases, but some machines have multiple buses of
a given type, some of which are dedicated to on-board devices and
some of which have an externally exposed connector for user-pluggable
devices. One example is I2C buses.
Provide a new function qbus_mark_full() so that a machine model can
mark this kind of "internal only" bus as 'full' after it has created
all the devices that should be plugged into that bus. The "find a
non-full bus" algorithm will then skip the internal-only bus when
looking for a place to plug in user-created devices.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
include/hw/qdev-core.h | 24 ++++++++++++++++++++++++
softmmu/qdev-monitor.c | 7 ++++++-
2 files changed, 30 insertions(+), 1 deletion(-)
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index bafc311bfa1..762f9584dde 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -264,6 +264,7 @@ struct BusState {
HotplugHandler *hotplug_handler;
int max_index;
bool realized;
+ bool full;
int num_children;
/*
@@ -798,6 +799,29 @@ static inline bool qbus_is_hotpluggable(BusState *bus)
return bus->hotplug_handler;
}
+/**
+ * qbus_mark_full: Mark this bus as full, so no more devices can be attached
+ * @bus: Bus to mark as full
+ *
+ * By default, QEMU will allow devices to be plugged into a bus up
+ * to the bus class's device count limit. Calling this function
+ * marks a particular bus as full, so that no more devices can be
+ * plugged into it. In particular this means that the bus will not
+ * be considered as a candidate for plugging in devices created by
+ * the user on the commandline or via the monitor.
+ * If a machine has multiple buses of a given type, such as I2C,
+ * where some of those buses in the real hardware are used only for
+ * internal devices and some are exposed via expansion ports, you
+ * can use this function to mark the internal-only buses as full
+ * after you have created all their internal devices. Then user
+ * created devices will appear on the expansion-port bus where
+ * guest software expects them.
+ */
+static inline void qbus_mark_full(BusState *bus)
+{
+ bus->full = true;
+}
+
void device_listener_register(DeviceListener *listener);
void device_listener_unregister(DeviceListener *listener);
diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
index a304754ab91..0705f008466 100644
--- a/softmmu/qdev-monitor.c
+++ b/softmmu/qdev-monitor.c
@@ -435,7 +435,12 @@ static DeviceState *qbus_find_dev(BusState *bus, char
*elem)
static inline bool qbus_is_full(BusState *bus)
{
- BusClass *bus_class = BUS_GET_CLASS(bus);
+ BusClass *bus_class;
+
+ if (bus->full) {
+ return true;
+ }
+ bus_class = BUS_GET_CLASS(bus);
return bus_class->max_dev && bus->num_children >= bus_class->max_dev;
}
--
2.20.1