kconfig: allow compiling out QEMU device tree code per target

Introduce a new Kconfig symbol, CONFIG_DEVICE_TREE, that specifies whether
to include the common device tree code in system/device_tree.c and to
link to libfdt.  For now, include it unconditionally if libfdt is
available.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Kconfig.host

@@ -23,6 +23,10 @@ config IVSHMEM
 config TPM
     bool
 
+config FDT
+    bool
+    select DEVICE_TREE
+
 config VHOST_USER
     bool
 

hw/core/Kconfig

@@ -4,8 +4,14 @@ config EMPTY_SLOT
 config PTIMER
     bool
 
+config DEVICE_TREE
+    bool
+    # fail the build if libfdt not found
+    depends on FDT
+
 config FITLOADER
     bool
+    depends on DEVICE_TREE
 
 config GENERIC_LOADER
     bool
@@ -14,13 +20,14 @@ config GENERIC_LOADER
 config GUEST_LOADER
     bool
     default y
-    depends on TCG
+    depends on TCG && DEVICE_TREE
 
 config OR_IRQ
     bool
 
 config PLATFORM_BUS
     bool
+    depends on DEVICE_TREE
 
 config REGISTER
     bool

hw/core/meson.build

@@ -16,7 +16,7 @@ common_ss.add(files('cpu-common.c'))
 common_ss.add(files('machine-smp.c'))
 system_ss.add(when: 'CONFIG_FITLOADER', if_true: files('loader-fit.c'))
 system_ss.add(when: 'CONFIG_GENERIC_LOADER', if_true: files('generic-loader.c'))
-system_ss.add(when: ['CONFIG_GUEST_LOADER', fdt], if_true: files('guest-loader.c'))
+system_ss.add(when: 'CONFIG_GUEST_LOADER', if_true: files('guest-loader.c'))
 system_ss.add(when: 'CONFIG_OR_IRQ', if_true: files('or-irq.c'))
 system_ss.add(when: 'CONFIG_PLATFORM_BUS', if_true: files('platform-bus.c'))
 system_ss.add(when: 'CONFIG_PTIMER', if_true: files('ptimer.c'))

include/monitor/hmp.h

@@ -180,5 +180,6 @@ void hmp_ioport_write(Monitor *mon, const QDict *qdict);
 void hmp_boot_set(Monitor *mon, const QDict *qdict);
 void hmp_info_mtree(Monitor *mon, const QDict *qdict);
 void hmp_info_cryptodev(Monitor *mon, const QDict *qdict);
+void hmp_dumpdtb(Monitor *mon, const QDict *qdict);
 
 #endif

include/sysemu/device_tree.h

@@ -134,7 +134,6 @@ int qemu_fdt_add_path(void *fdt, const char *path);
     } while (0)
 
 void qemu_fdt_dumpdtb(void *fdt, int size);
-void hmp_dumpdtb(Monitor *mon, const QDict *qdict);
 
 /**
  * qemu_fdt_setprop_sized_cells_from_array:

meson.build

@@ -2989,6 +2989,7 @@ host_kconfig = \
   (have_ivshmem ? ['CONFIG_IVSHMEM=y'] : []) + \
   (opengl.found() ? ['CONFIG_OPENGL=y'] : []) + \
   (x11.found() ? ['CONFIG_X11=y'] : []) + \
+  (fdt.found() ? ['CONFIG_FDT=y'] : []) + \
   (have_vhost_user ? ['CONFIG_VHOST_USER=y'] : []) + \
   (have_vhost_vdpa ? ['CONFIG_VHOST_VDPA=y'] : []) + \
   (have_vhost_kernel ? ['CONFIG_VHOST_KERNEL=y'] : []) + \

monitor/hmp-cmds.c

@@ -22,6 +22,7 @@
 #include "monitor/monitor-internal.h"
 #include "qapi/error.h"
 #include "qapi/qapi-commands-control.h"
+#include "qapi/qapi-commands-machine.h"
 #include "qapi/qapi-commands-misc.h"
 #include "qapi/qmp/qdict.h"
 #include "qemu/cutils.h"
@@ -443,3 +444,19 @@ void hmp_info_mtree(Monitor *mon, const QDict *qdict)
 
     mtree_info(flatview, dispatch_tree, owner, disabled);
 }
+
+#if defined(CONFIG_FDT)
+void hmp_dumpdtb(Monitor *mon, const QDict *qdict)
+{
+    const char *filename = qdict_get_str(qdict, "filename");
+    Error *local_err = NULL;
+
+    qmp_dumpdtb(filename, &local_err);
+
+    if (hmp_handle_error(mon, local_err)) {
+        return;
+    }
+
+    monitor_printf(mon, "dtb dumped to %s", filename);
+}
+#endif

system/device_tree-stub.c

@@ -0,0 +1,10 @@
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qapi/qapi-commands-machine.h"
+
+#ifdef CONFIG_FDT
+void qmp_dumpdtb(const char *filename, Error **errp)
+{
+    error_setg(errp, "This machine doesn't have a FDT");
+}
+#endif

system/device_tree.c

@@ -668,20 +668,6 @@ void qmp_dumpdtb(const char *filename, Error **errp)
     }
 }
 
-void hmp_dumpdtb(Monitor *mon, const QDict *qdict)
-{
-    const char *filename = qdict_get_str(qdict, "filename");
-    Error *local_err = NULL;
-
-    qmp_dumpdtb(filename, &local_err);
-
-    if (hmp_handle_error(mon, local_err)) {
-        return;
-    }
-
-    info_report("dtb dumped to %s", filename);
-}
-
 void qemu_fdt_randomize_seeds(void *fdt)
 {
     int noffset, poffset, len;

system/meson.build

@@ -32,7 +32,9 @@ if have_tpm
 endif
 
 system_ss.add(when: seccomp, if_true: files('qemu-seccomp.c'))
-system_ss.add(when: fdt, if_true: files('device_tree.c'))
+system_ss.add(when: 'CONFIG_DEVICE_TREE',
+              if_true: [fdt, files('device_tree.c')],
+              if_false: files('device_tree-stub.c'))
 if host_os == 'linux'
   system_ss.add(files('async-teardown.c'))
 endif