hw: Centralize handling of -machine dumpdtb option

Currently we handle the 'dumpdtb' machine sub-option ad-hoc in every
board model that has an FDT.  It's up to the board code to make sure
it calls qemu_fdt_dumpdtb() in the right place.

This means we're inconsistent and often just ignore the user's
command line argument:
 * if the board doesn't have an FDT at all
 * if the board supports FDT, but there happens not to be one
   present (usually because of a missing -fdt option)

This isn't very helpful because it gives the user no clue why their
option was ignored.

However, in order to support the QMP/HMP dumpdtb commands we require
now that every FDT machine stores a pointer to the FDT in
MachineState::fdt.  This means we can handle -machine dumpdtb
centrally by calling the qmp_dumpdtb() function, unifying its
handling with the QMP/HMP commands.  All the board code calls to
qemu_fdt_dumpdtb() can then be removed.

For this commit we retain the existing behaviour that if there
is no FDT we silently ignore the -machine dumpdtb option.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 02cff735b3..61c22f723a 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -19,6 +19,7 @@
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "qapi/qapi-visit-machine.h"
+#include "qapi/qapi-commands-machine.h"
 #include "qemu/madvise.h"
 #include "qom/object_interfaces.h"
 #include "system/cpus.h"
@@ -1696,6 +1697,24 @@ void qemu_remove_machine_init_done_notifier(Notifier *notify)
     notifier_remove(notify);
 }
 
+static void handle_machine_dumpdtb(MachineState *ms)
+{
+    if (!ms->dumpdtb) {
+        return;
+    }
+    if (!ms->fdt) {
+        /* Silently ignore dumpdtb option if there is nothing to dump */
+        return;
+    }
+#ifdef CONFIG_FDT
+    qmp_dumpdtb(ms->dumpdtb, &error_fatal);
+    exit(0);
+#else
+    error_report("This machine doesn't have an FDT");
+    exit(1);
+#endif
+}
+
 void qdev_machine_creation_done(void)
 {
     cpu_synchronize_all_post_init();
@@ -1712,6 +1731,12 @@ void qdev_machine_creation_done(void)
     phase_advance(PHASE_MACHINE_READY);
     qdev_assert_realized_properly();
 
+    /*
+     * If the user used -machine dumpdtb=file.dtb to request that we
+     * dump the DTB to a file,  do it now, and exit.
+     */
+    handle_machine_dumpdtb(current_machine);
+
     /* TODO: once all bus devices are qdevified, this should be done
      * when bus is created by qdev.c */
     /*