Re: [PATCH for-7.2 04/10] hmp, device_tree.c: introduce fdt-save

[Daniel Henrique Barboza]

On 7/22/22 20:13, BALATON Zoltan wrote:

On Fri, 22 Jul 2022, Daniel Henrique Barboza wrote:

To save the FDT blob we have the '-machine dumpdtb=<file>' property. With this
property set, the machine saves the FDT in <file> and exit. The created
file can then be converted to plain text dts format using 'dtc'.

There's nothing particularly sophisticated into saving the FDT that
can't be done with the machine at any state, as long as the machine has
a valid FDT to be saved.

The 'fdt-save' command receives a 'filename' paramenter and, if a valid
FDT is available, it'll save it in a file 'filename'. In short, this is
a '-machine dumpdtb' that can be fired on demand via HMP.

If it does the same as -machine dumpdtb wouldn't it be more intuitive to call 
the HMP command the same, so either dumpdtb or machine-dumpdtb or similar? That 
way it's more obvious that these do the same.

Good point. I'll rename 'fdt-save' to 'dumpdtb'.


Daniel

Regards,
BALATON Zoltan

A valid FDT consists of a FDT that was created using libfdt being
retrieved via 'current_machine->fdt' in device_tree.c. This condition is
met by most FDT users in QEMU.

Cc: Dr. David Alan Gilbert <dgilb...@redhat.com>
Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
---
hmp-commands.hx              | 13 +++++++++++++
include/sysemu/device_tree.h |  2 ++
monitor/misc.c               | 13 +++++++++++++
softmmu/device_tree.c        | 18 ++++++++++++++++++
4 files changed, 46 insertions(+)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index c9d465735a..3c134cf652 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1768,3 +1768,16 @@ ERST
                      "\n\t\t\t -b to specify dirty bitmap as method of 
calculation)",
        .cmd        = hmp_calc_dirty_rate,
    },
+
+    {
+        .name       = "fdt-save",
+        .args_type  = "filename:s",
+        .params     = "[filename] file to save the FDT",
+        .help       = "save the FDT in the 'filename' file to be decoded using 
dtc",
+        .cmd        = hmp_fdt_save,
+    },
+
+SRST
+``fdt-save`` *filename*
+  Save the FDT in the 'filename' file to be decoded using dtc
+ERST
diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
index ef060a9759..1397adb21c 100644
--- a/include/sysemu/device_tree.h
+++ b/include/sysemu/device_tree.h
@@ -123,6 +123,8 @@ int qemu_fdt_nop_node(void *fdt, const char *node_path);
int qemu_fdt_add_subnode(void *fdt, const char *name);
int qemu_fdt_add_path(void *fdt, const char *path);

+void fdt_save(const char *filename, Error **errp);
+
#define qemu_fdt_setprop_cells(fdt, node_path, property, ...)                 \
    do {                                                                      \
        uint32_t qdt_tmp[] = { __VA_ARGS__ };                                 \
diff --git a/monitor/misc.c b/monitor/misc.c
index 3d2312ba8d..145285cec0 100644
--- a/monitor/misc.c
+++ b/monitor/misc.c
@@ -78,6 +78,7 @@
#include "qapi/qmp-event.h"
#include "sysemu/cpus.h"
#include "qemu/cutils.h"
+#include "sysemu/device_tree.h"

#if defined(TARGET_S390X)
#include "hw/s390x/storage-keys.h"
@@ -936,6 +937,18 @@ static void hmp_boot_set(Monitor *mon, const QDict *qdict)
    }
}

+static void hmp_fdt_save(Monitor *mon, const QDict *qdict)
+{
+    const char *path = qdict_get_str(qdict, "filename");
+    Error *local_err = NULL;
+
+    fdt_save(path, &local_err);
+
+    if (local_err) {
+        error_report_err(local_err);
+    }
+}
+
static void hmp_info_mtree(Monitor *mon, const QDict *qdict)
{
    bool flatview = qdict_get_try_bool(qdict, "flatview", false);
diff --git a/softmmu/device_tree.c b/softmmu/device_tree.c
index 6ca3fad285..eeab6a5ef0 100644
--- a/softmmu/device_tree.c
+++ b/softmmu/device_tree.c
@@ -643,3 +643,21 @@ out:
    g_free(propcells);
    return ret;
}
+
+void fdt_save(const char *filename, Error **errp)
+{
+    int size;
+
+    if (!current_machine->fdt) {
+        error_setg(errp, "Unable to find the machine FDT");
+        return;
+    }
+
+    size = fdt_totalsize(current_machine->fdt);
+
+    if (g_file_set_contents(filename, current_machine->fdt, size, NULL)) {
+        return;
+    }
+
+    error_setg(errp, "Error when saving machine FDT to file %s", filename);
+}