3 files changed, 73 insertions, 2 deletions
diff --git a/hw/tpm/Makefile.objs b/hw/tpm/Makefile.objs
index 41f0b7a..7a93b24 100644
--- a/hw/tpm/Makefile.objs
+++ b/hw/tpm/Makefile.objs
@@ -1,3 +1,4 @@
+common-obj-y += tpm_util.o
 common-obj-$(CONFIG_TPM_TIS) += tpm_tis.o
-common-obj-$(CONFIG_TPM_PASSTHROUGH) += tpm_passthrough.o tpm_util.o
-common-obj-$(CONFIG_TPM_EMULATOR) += tpm_emulator.o tpm_util.o
+common-obj-$(CONFIG_TPM_PASSTHROUGH) += tpm_passthrough.o
+common-obj-$(CONFIG_TPM_EMULATOR) += tpm_emulator.o
diff --git a/hw/tpm/tpm_util.c b/hw/tpm/tpm_util.c
index a317243..17cafbe 100644
--- a/hw/tpm/tpm_util.c
+++ b/hw/tpm/tpm_util.c
@@ -21,9 +21,13 @@
 
 #include "qemu/osdep.h"
 #include "qemu/error-report.h"
+#include "qapi/error.h"
+#include "qapi/visitor.h"
 #include "tpm_util.h"
 #include "tpm_int.h"
 #include "exec/memory.h"
+#include "sysemu/tpm_backend.h"
+#include "hw/qdev.h"
 
 #define DEBUG_TPM 0
 
@@ -33,6 +37,69 @@
     } \
 } while (0)
 
+/* tpm backend property */
+
+static void get_tpm(Object *obj, Visitor *v, const char *name, void *opaque,
+                    Error **errp)
+{
+    DeviceState *dev = DEVICE(obj);
+    TPMBackend **be = qdev_get_prop_ptr(dev, opaque);
+    char *p;
+
+    p = g_strdup(*be ? (*be)->id : "");
+    visit_type_str(v, name, &p, errp);
+    g_free(p);
+}
+
+static void set_tpm(Object *obj, Visitor *v, const char *name, void *opaque,
+                    Error **errp)
+{
+    DeviceState *dev = DEVICE(obj);
+    Error *local_err = NULL;
+    Property *prop = opaque;
+    TPMBackend *s, **be = qdev_get_prop_ptr(dev, prop);
+    char *str;
+
+    if (dev->realized) {
+        qdev_prop_set_after_realize(dev, name, errp);
+        return;
+    }
+
+    visit_type_str(v, name, &str, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    s = qemu_find_tpm_be(str);
+    if (s == NULL) {
+        error_setg(errp, "Property '%s.%s' can't find value '%s'",
+                   object_get_typename(obj), prop->name, str);
+    } else if (tpm_backend_init(s, TPM_IF(obj), errp) == 0) {
+        *be = s; /* weak reference, avoid cyclic ref */
+    }
+    g_free(str);
+}
+
+static void release_tpm(Object *obj, const char *name, void *opaque)
+{
+    DeviceState *dev = DEVICE(obj);
+    Property *prop = opaque;
+    TPMBackend **be = qdev_get_prop_ptr(dev, prop);
+
+    if (*be) {
+        tpm_backend_reset(*be);
+    }
+}
+
+const PropertyInfo qdev_prop_tpm = {
+    .name  = "str",
+    .description = "ID of a tpm to use as a backend",
+    .get   = get_tpm,
+    .set   = set_tpm,
+    .release = release_tpm,
+};
+
 /*
  * Write an error message in the given output buffer.
  */
diff --git a/hw/tpm/tpm_util.h b/hw/tpm/tpm_util.h
index 1c17e39..2393b6b 100644
--- a/hw/tpm/tpm_util.h
+++ b/hw/tpm/tpm_util.h
@@ -39,4 +39,7 @@ static inline uint32_t tpm_cmd_get_size(const void *b)
 int tpm_util_get_buffer_size(int tpm_fd, TPMVersion tpm_version,
                              size_t *buffersize);
 
+#define DEFINE_PROP_TPMBE(_n, _s, _f)                     \
+    DEFINE_PROP(_n, _s, _f, qdev_prop_tpm, TPMBackend *)
+
 #endif /* TPM_TPM_UTIL_H */