hw/i386/acpi: Add object_resolve_type_unambiguous to improve modularity

When building with CONFIG_Q35=n, we get:

    LINK    x86_64-softmmu/qemu-system-x86_64
  /usr/bin/ld: hw/i386/acpi-build.o: in function `acpi_get_misc_info':
  /source/qemu/hw/i386/acpi-build.c:243: undefined reference to `ich9_lpc_find'
  collect2: error: ld returned 1 exit status
  make[1]: *** [Makefile:204: qemu-system-x86_64] Error 1

This is due to a dependency in acpi-build.c on the ICH9_LPC
(via ich9_lpc_find) and PIIX4_PM (via piix4_pm_find) devices.

To allow better modularity (compile acpi-build.c with only
Q35/ICH9 or ISAPC/PIIX4), refactor the similar helper as
object_resolve_type_unambiguous(). This way we relax the
linker dependencies and can build the x86 targets with a
selection of machines (instead of all of them).

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190427144025.22880-3-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/acpi/piix4.c

@@ -552,17 +552,6 @@ static void piix4_pm_realize(PCIDevice *dev, Error **errp)
     piix4_pm_add_propeties(s);
 }
 
-Object *piix4_pm_find(void)
-{
-    bool ambig;
-    Object *o = object_resolve_path_type("", TYPE_PIIX4_PM, &ambig);
-
-    if (ambig || !o) {
-        return NULL;
-    }
-    return o;
-}
-
 I2CBus *piix4_pm_init(PCIBus *bus, int devfn, uint32_t smb_io_base,
                       qemu_irq sci_irq, qemu_irq smi_irq,
                       int smm_enabled, DeviceState **piix4_pm)

hw/i386/acpi-build.c

@@ -35,6 +35,7 @@
 #include "hw/acpi/acpi-defs.h"
 #include "hw/acpi/acpi.h"
 #include "hw/acpi/cpu.h"
+#include "hw/acpi/piix4.h"
 #include "hw/nvram/fw_cfg.h"
 #include "hw/acpi/bios-linker-loader.h"
 #include "hw/loader.h"
@@ -164,10 +165,21 @@ static void init_common_fadt_data(Object *o, AcpiFadtData *data)
     *data = fadt;
 }
 
+static Object *object_resolve_type_unambiguous(const char *typename)
+{
+    bool ambig;
+    Object *o = object_resolve_path_type("", typename, &ambig);
+
+    if (ambig || !o) {
+        return NULL;
+    }
+    return o;
+}
+
 static void acpi_get_pm_info(AcpiPmInfo *pm)
 {
-    Object *piix = piix4_pm_find();
-    Object *lpc = ich9_lpc_find();
+    Object *piix = object_resolve_type_unambiguous(TYPE_PIIX4_PM);
+    Object *lpc = object_resolve_type_unambiguous(TYPE_ICH9_LPC_DEVICE);
     Object *obj = piix ? piix : lpc;
     QObject *o;
     pm->cpu_hp_io_base = 0;
@@ -228,8 +240,8 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)
 
 static void acpi_get_misc_info(AcpiMiscInfo *info)
 {
-    Object *piix = piix4_pm_find();
-    Object *lpc = ich9_lpc_find();
+    Object *piix = object_resolve_type_unambiguous(TYPE_PIIX4_PM);
+    Object *lpc = object_resolve_type_unambiguous(TYPE_ICH9_LPC_DEVICE);
     assert(!!piix != !!lpc);
 
     if (piix) {

hw/isa/lpc_ich9.c

@@ -624,17 +624,6 @@ static const MemoryRegionOps ich9_rst_cnt_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN
 };
 
-Object *ich9_lpc_find(void)
-{
-    bool ambig;
-    Object *o = object_resolve_path_type("", TYPE_ICH9_LPC_DEVICE, &ambig);
-
-    if (ambig) {
-        return NULL;
-    }
-    return o;
-}
-
 static void ich9_lpc_get_sci_int(Object *obj, Visitor *v, const char *name,
                                  void *opaque, Error **errp)
 {

include/hw/acpi/piix4.h

@@ -3,6 +3,4 @@
 
 #define TYPE_PIIX4_PM "PIIX4_PM"
 
-Object *piix4_pm_find(void);
-
 #endif

include/hw/i386/ich9.h

@@ -81,8 +81,6 @@ typedef struct ICH9LPCState {
     qemu_irq gsi[GSI_NUM_PINS];
 } ICH9LPCState;
 
-Object *ich9_lpc_find(void);
-
 #define Q35_MASK(bit, ms_bit, ls_bit) \
 ((uint##bit##_t)(((1ULL << ((ms_bit) + 1)) - 1) & ~((1ULL << ls_bit) - 1)))