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 <dgilbert@redhat.com>
> > Signed-off-by: Daniel Henrique Barboza <danielhb413@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);
> > +}