[Qemu-devel] [RFC PATCH V4 1/6] qdev : add a maximum device allowed field for the bus.

[fred.konrad@greensocs.com]

From: KONRAD Frederic <fred.konrad@greensocs.com>

Only one device can be connected to virtio-bus.
This patch add a field max_dev which is :
    * the maximum amount of devices connected on the bus ( when
    * max_dev!=0 ).
    * have no effect ( when max_dev=0 ).

The function qbus_find_recursive is modified :
    * to return a non full bus when the "bus=" option is not present.
    * to give an error when the "bus=" option is pointing a full bus.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
---
 hw/qdev-core.h    |    2 ++
 hw/qdev-monitor.c |   11 +++++++++++
 qerror.h          |    3 +++
 3 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/hw/qdev-core.h b/hw/qdev-core.h
index fff7f0f..f5019b1 100644
--- a/hw/qdev-core.h
+++ b/hw/qdev-core.h
@@ -113,6 +113,8 @@ struct BusState {
     const char *name;
     int allow_hotplug;
     int max_index;
+    /* maximum devices allowed on the bus. */
+    int max_dev;
     QTAILQ_HEAD(ChildrenHead, BusChild) children;
     QLIST_ENTRY(BusState) sibling;
 };
diff --git a/hw/qdev-monitor.c b/hw/qdev-monitor.c
index a1b4d6a..4471b3a 100644
--- a/hw/qdev-monitor.c
+++ b/hw/qdev-monitor.c
@@ -292,6 +292,17 @@ static BusState *qbus_find_recursive(BusState *bus, const char *name,
     if (bus_typename && !object_dynamic_cast(OBJECT(bus), bus_typename)) {
         match = 0;
     }
+    /* Check if max_dev is reached */
+    if ((bus->max_dev != 0) && (bus->max_dev <= bus->max_index)) {
+        if (name != NULL) {
+            /* bus was explicitly specified : return an error. */
+            qerror_report(QERR_BUS_IS_FULL, bus->name);
+            return NULL;
+        } else {
+            /* bus was not specified : try to find another one. */
+            match = 0;
+        }
+    }
     if (match) {
         return bus;
     }
diff --git a/qerror.h b/qerror.h
index 8db4309..b159828 100644
--- a/qerror.h
+++ b/qerror.h
@@ -69,6 +69,9 @@ void assert_no_error(Error *err);
 #define QERR_BUS_NOT_FOUND \
     ERROR_CLASS_GENERIC_ERROR, "Bus '%s' not found"
 
+#define QERR_BUS_IS_FULL \
+    ERROR_CLASS_GENERIC_ERROR, "Bus '%s' is full"
+
 #define QERR_COMMAND_DISABLED \
     ERROR_CLASS_GENERIC_ERROR, "The command %s has been disabled for this instance"
 
-- 
1.7.1