[Qemu-devel] [PATCH v3 5/6] hw/core: explicit OFW unit address property for SysBusDevice

[Laszlo Ersek <lersek@redhat.com>]

The sysbus_get_fw_dev_path() function formats OpenFirmware device path
nodes ("driver-name@unit-address") for sysbus devices. The first choice
for "unit-address" is the base address of the device's first MMIO region.
The second choice is its first IO port.

However, if two sysbus devices with the same "driver-name" lack both MMIO
and PIO resources, then there is no good way to distinguish them based on
their OFW nodes, because in this case unit-address is omitted completely
for both devices.

For such devices, delegate a fallback property,
"explicit_ofw_unit_address", to whoever creates the device. The creator
can set the property to any appropriate value.

Cc: Markus Armbruster <armbru@redhat.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v3:
    - new in v3
    - new approach

 include/hw/sysbus.h |  8 ++++++++
 hw/core/sysbus.c    | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/hw/sysbus.h b/include/hw/sysbus.h
index d1f3f00..de41b06 100644
--- a/include/hw/sysbus.h
+++ b/include/hw/sysbus.h
@@ -55,6 +55,14 @@ struct SysBusDevice {
     } mmio[QDEV_MAX_MMIO];
     int num_pio;
     pio_addr_t pio[QDEV_MAX_PIO];
+
+    /*
+     * Sometimes a SysBusDevice has neither MMIO nor PIO resources, yet it
+     * would like to distinguish itself, in OpenFirmware device paths, from
+     * other instances of the same class on the same sysbus. For that end we
+     * expose this property.
+     */
+    char *explicit_ofw_unit_address;
 };
 
 typedef int FindSysbusDeviceFunc(SysBusDevice *sbdev, void *opaque);
diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
index 0ebb4e2..6e9af1c 100644
--- a/hw/core/sysbus.c
+++ b/hw/core/sysbus.c
@@ -289,6 +289,10 @@ static char *sysbus_get_fw_dev_path(DeviceState *dev)
     if (s->num_pio) {
         return g_strdup_printf("%s@i%04x", qdev_fw_name(dev), s->pio[0]);
     }
+    if (s->explicit_ofw_unit_address) {
+        return g_strdup_printf("%s@%s", qdev_fw_name(dev),
+                               s->explicit_ofw_unit_address);
+    }
     return g_strdup(qdev_fw_name(dev));
 }
 
@@ -303,11 +307,18 @@ MemoryRegion *sysbus_address_space(SysBusDevice *dev)
     return get_system_memory();
 }
 
+static Property sysbus_device_properties[] = {
+    DEFINE_PROP_STRING("explicit_ofw_unit_address", SysBusDevice,
+                       explicit_ofw_unit_address),
+    DEFINE_PROP_END_OF_LIST()
+};
+
 static void sysbus_device_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *k = DEVICE_CLASS(klass);
     k->init = sysbus_device_init;
     k->bus_type = TYPE_SYSTEM_BUS;
+    k->props = sysbus_device_properties;
 }
 
 static const TypeInfo sysbus_device_type_info = {
-- 
1.8.3.1