[Qemu-devel] [PATCH v4 3/4] hw/core: explicit OFW unit address callback for SysBusDeviceClass

[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 the sake of such devices, introduce the explicit_ofw_unit_address()
"virtual member function". With this function, each sysbus device in the
same SysBusDeviceClass can state its own address.

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:
    v4:
    - Yet another approach. Instead of allowing the creator of the device to
      set a string property statically, introduce a class level callback.
    
    v3:
    - new in v3
    - new approach

 include/hw/sysbus.h |  9 +++++++++
 hw/core/sysbus.c    | 13 +++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/include/hw/sysbus.h b/include/hw/sysbus.h
index d1f3f00..63b036b 100644
--- a/include/hw/sysbus.h
+++ b/include/hw/sysbus.h
@@ -41,6 +41,15 @@ typedef struct SysBusDeviceClass {
     /*< public >*/
 
     int (*init)(SysBusDevice *dev);
+
+    /*
+     * Sometimes a class of SysBusDevices has neither MMIO nor PIO resources,
+     * yet instances of it would like to distinguish themselves, in
+     * OpenFirmware device paths, from other instances of the same class on the
+     * same sysbus. For that end we expose this callback. It returns a
+     * dynamically allocated string.
+     */
+    char *(*explicit_ofw_unit_address)(SysBusDevice *dev);
 } SysBusDeviceClass;
 
 struct SysBusDevice {
diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
index 0ebb4e2..a0ec814 100644
--- a/hw/core/sysbus.c
+++ b/hw/core/sysbus.c
@@ -281,6 +281,7 @@ static void sysbus_dev_print(Monitor *mon, DeviceState *dev, int indent)
 static char *sysbus_get_fw_dev_path(DeviceState *dev)
 {
     SysBusDevice *s = SYS_BUS_DEVICE(dev);
+    SysBusDeviceClass *sbc = SYS_BUS_DEVICE_GET_CLASS(s);
 
     if (s->num_mmio) {
         return g_strdup_printf("%s@"TARGET_FMT_plx, qdev_fw_name(dev),
@@ -289,6 +290,18 @@ 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 (sbc->explicit_ofw_unit_address) {
+        char *addr;
+
+        addr = sbc->explicit_ofw_unit_address(s);
+        if (addr) {
+            char *fw_dev_path;
+
+            fw_dev_path = g_strdup_printf("%s@%s", qdev_fw_name(dev), addr);
+            g_free(addr);
+            return fw_dev_path;
+        }
+    }
     return g_strdup(qdev_fw_name(dev));
 }
 
-- 
1.8.3.1