[PATCH v3 1/4] hw/isa: add function to check for existence of device by its type

[Liav Albani <liavalb@gmail.com>]

This function enumerates all attached ISA devices in the machine, and
tries to compare a given device type name to the enumerated devices.
For example, this can help other code to determine if a i8042 controller
exists in the machine.

Signed-off-by: Liav Albani <liavalb@gmail.com>
---
 hw/isa/isa-bus.c     | 23 +++++++++++++++++++++++
 include/hw/isa/isa.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/hw/isa/isa-bus.c b/hw/isa/isa-bus.c
index 6c31398dda..663aa36d29 100644
--- a/hw/isa/isa-bus.c
+++ b/hw/isa/isa-bus.c
@@ -222,6 +222,29 @@ void isa_build_aml(ISABus *bus, Aml *scope)
     }
 }
 
+bool isa_check_device_existence(const char *typename)
+{
+    /*
+     * If there's no ISA bus, we know for sure that the checked ISA device type
+     * doesn't exist in the machine.
+     */
+    if (isabus == NULL) {
+        return false;
+    }
+
+    BusChild *kid;
+    ISADevice *dev;
+
+    QTAILQ_FOREACH(kid, &isabus->parent_obj.children, sibling) {
+        dev = ISA_DEVICE(kid->child);
+        const char *object_type = object_get_typename(OBJECT(dev));
+        if (object_type && strcmp(object_type, typename) == 0) {
+            return true;
+        }
+    }
+    return false;
+}
+
 static void isabus_dev_print(Monitor *mon, DeviceState *dev, int indent)
 {
     ISADevice *d = ISA_DEVICE(dev);
diff --git a/include/hw/isa/isa.h b/include/hw/isa/isa.h
index d4417b34b6..65f0c7e28c 100644
--- a/include/hw/isa/isa.h
+++ b/include/hw/isa/isa.h
@@ -99,6 +99,7 @@ IsaDma *isa_get_dma(ISABus *bus, int nchan);
 MemoryRegion *isa_address_space(ISADevice *dev);
 MemoryRegion *isa_address_space_io(ISADevice *dev);
 ISADevice *isa_new(const char *name);
+bool isa_check_device_existence(const char *typename);
 ISADevice *isa_try_new(const char *name);
 bool isa_realize_and_unref(ISADevice *dev, ISABus *bus, Error **errp);
 ISADevice *isa_create_simple(ISABus *bus, const char *name);
-- 
2.35.1