Re: [RFC PATCH v2 1/6] device_tree: Add qemu_fdt_add_path

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Apr 13, 2021 at 04:07:40PM +0800, Yanan Wang wrote:
> From: Andrew Jones <drjones@redhat.com>
> 
> qemu_fdt_add_path() works like qemu_fdt_add_subnode(), except
> it also adds any missing subnodes in the path. We also tweak
> an error message of qemu_fdt_add_subnode().
> 
> We'll make use of this new function in a coming patch.
> 
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
>  include/sysemu/device_tree.h |  1 +
>  softmmu/device_tree.c        | 45 ++++++++++++++++++++++++++++++++++--
>  2 files changed, 44 insertions(+), 2 deletions(-)
> 
> diff --git a/include/sysemu/device_tree.h b/include/sysemu/device_tree.h
> index 8a2fe55622..ef060a9759 100644
> --- a/include/sysemu/device_tree.h
> +++ b/include/sysemu/device_tree.h
> @@ -121,6 +121,7 @@ uint32_t qemu_fdt_get_phandle(void *fdt, const char *path);
>  uint32_t qemu_fdt_alloc_phandle(void *fdt);
>  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);
>  
>  #define qemu_fdt_setprop_cells(fdt, node_path, property, ...)                 \
>      do {                                                                      \
> diff --git a/softmmu/device_tree.c b/softmmu/device_tree.c
> index 2691c58cf6..8592c7aa1b 100644
> --- a/softmmu/device_tree.c
> +++ b/softmmu/device_tree.c
> @@ -541,8 +541,8 @@ int qemu_fdt_add_subnode(void *fdt, const char *name)
>  
>      retval = fdt_add_subnode(fdt, parent, basename);
>      if (retval < 0) {
> -        error_report("FDT: Failed to create subnode %s: %s", name,
> -                     fdt_strerror(retval));
> +        error_report("%s: Failed to create subnode %s: %s",
> +                     __func__, name, fdt_strerror(retval));
>          exit(1);
>      }
>  
> @@ -550,6 +550,47 @@ int qemu_fdt_add_subnode(void *fdt, const char *name)
>      return retval;
>  }
>  
> +/*
> + * Like qemu_fdt_add_subnode(), but will add all missing
> + * subnodes in the path.
> + */
> +int qemu_fdt_add_path(void *fdt, const char *path)
> +{
> +    char *dupname, *basename, *p;
> +    int parent, retval = -1;
> +
> +    if (path[0] != '/') {
> +        return retval;
> +    }
> +
> +    parent = fdt_path_offset(fdt, "/");

Getting the offset for "/" is never needed - it's always 0.

> +    p = dupname = g_strdup(path);

You shouldn't need the strdup(), see below.

> +
> +    while (p) {
> +        *p = '/';
> +        basename = p + 1;
> +        p = strchr(p + 1, '/');
> +        if (p) {
> +            *p = '\0';
> +        }
> +        retval = fdt_path_offset(fdt, dupname);

The fdt_path_offset_namelen() function exists *exactly* so that you
can look up partial parths without having to mangle your input
string.  Just set the namelen right, and it will ignore anything to
the right of that.

> +        if (retval < 0 && retval != -FDT_ERR_NOTFOUND) {
> +            error_report("%s: Invalid path %s: %s",
> +                         __func__, path, fdt_strerror(retval));

If you're getting an error other than FDT_ERR_NOTFOUND here, chances
are it's not an invalid path, but a corrupted fdt blob or something
else.

> +            exit(1);
> +        } else if (retval == -FDT_ERR_NOTFOUND) {
> +            retval = fdt_add_subnode(fdt, parent, basename);
> +            if (retval < 0) {
> +                break;
> +            }
> +        }
> +        parent = retval;
> +    }
> +
> +    g_free(dupname);
> +    return retval;
> +}
> +
>  void qemu_fdt_dumpdtb(void *fdt, int size)
>  {
>      const char *dumpdtb = current_machine->dumpdtb;

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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