Re: [PATCH for-7.2 v2 16/20] device_tree.c: support string props in fdt_format_node()

[Daniel Henrique Barboza]

On 8/8/22 01:36, David Gibson wrote:
> On Fri, Aug 05, 2022 at 06:39:44AM -0300, Daniel Henrique Barboza wrote:
> > To support printing string properties in 'info fdt' we need to determine
> > whether a void data might contain a string.
>
> Oh... sorry, obviously I hadn't read these later patches when I
> complained about the command not printing property values.
>
> > We do that by casting the void data to a string array and:
> >
> > - check if the array finishes with a null character
> > - check if all characters are printable
>
> This won't handle the case of the "string list" several strings tacked
> together, separated by their terminating \0 characters.

Hmmmm how is this printed? Should we concatenate them? Replace the \0
with a whitespace? Or ignore the zero and concatenate them?

E.g. this is a\0string\0list

Should we print it as:

this is astringlist

or

this is a string list ?


Thanks,


Daniel


> > If both conditions are met, we'll consider it to be a string data type
> > and print it accordingly. After this change, 'info fdt' is now able to
> > print string properties. Here's an example with the ARM 'virt' machine:
> >
> > (qemu) info fdt /chosen
> > chosen {
> >      stdout-path = '/pl011@9000000'
> >      rng-seed;
> >      kaslr-seed;
> > }
> >
> > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> > ---
> >   softmmu/device_tree.c | 25 ++++++++++++++++++++++++-
> >   1 file changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/softmmu/device_tree.c b/softmmu/device_tree.c
> > index 3fb07b537f..8691c3ccc0 100644
> > --- a/softmmu/device_tree.c
> > +++ b/softmmu/device_tree.c
> > @@ -663,6 +663,24 @@ void qemu_fdt_qmp_dumpdtb(const char *filename, Error 
> > **errp)
> >       error_setg(errp, "Error when saving machine FDT to file %s", filename);
> >   }
> >   
> > +static bool fdt_prop_is_string(const void *data, int size)
> > +{
> > +    const char *str = data;
> > +    int i;
> > +
> > +    if (size <= 0 || str[size - 1] != '\0') {
> > +        return false;
> > +    }
> > +
> > +    for (i = 0; i < size - 1; i++) {
> > +        if (!g_ascii_isprint(str[i])) {
> > +            return false;
> > +        }
> > +    }
> > +
> > +    return true;
> > +}
> > +
> >   static void fdt_format_node(GString *buf, int node, int depth)
> >   {
> >       const struct fdt_property *prop = NULL;
> > @@ -681,7 +699,12 @@ static void fdt_format_node(GString *buf, int node, int 
> > depth)
> >           prop = fdt_get_property_by_offset(fdt, property, &prop_size);
> >           propname = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
> >   
> > -        g_string_append_printf(buf, "%*s%s;\n", padding, "", propname);
> > +        if (fdt_prop_is_string(prop->data, prop_size)) {
> > +            g_string_append_printf(buf, "%*s%s = '%s'\n",
> > +                                   padding, "", propname, prop->data);
>
> If you're going for dts like output, I'd suggest going all the way.
> That means \" instead of \' and a ';' at the end of the line.
>
> > +        } else {
> > +            g_string_append_printf(buf, "%*s%s;\n", padding, "", propname);
> > +        }
> >       }
> >   
> >       padding -= 4;