[PATCH v2 30/32] fdt: Allow the devicetree to come from a bloblist

[Ilias Apalodimas]

Hi Simon,

I commented on the v1 thread, but let's continue the discussion here

On Thu, 21 Sept 2023 at 04:58, Simon Glass <sjg at chromium.org> wrote:
>
> Standard passage provides for a bloblist to be passed from one firmware
> phase to the next. That can be used to pass the devicetree along as well.
> Add an option to support this.
>
> Tests for this will be added as part of the Universal Payload work.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
> Changes in v2:
> - No changes as it still seems unclear what should be done
>

[...]

>
>         /* BLOBLISTT_VENDOR_AREA */
> diff --git a/doc/develop/devicetree/control.rst b/doc/develop/devicetree/control.rst
> index cbb65c9b177f..56e00090166f 100644
> --- a/doc/develop/devicetree/control.rst
> +++ b/doc/develop/devicetree/control.rst
> @@ -108,6 +108,9 @@ If CONFIG_OF_BOARD is defined, a board-specific routine will provide the
>  devicetree at runtime, for example if an earlier bootloader stage creates
>  it and passes it to U-Boot.
>
> +If CONFIG_OF_BLOBLIST is defined, the devicetree comes from a bloblist passed
> +from a previous stage.

What I argued before is that we don't need to be this explicit.
The bloblist can carry a bunch of options that might be used by
U-Boot.  It would be better if we had a more generic approach instead
of adding Kconfig options per bloblist entry

[...]

>  #ifndef USE_HOSTCC
> +
> +#define LOG_CATEGORY   LOGC_DT
> +
>  #include <common.h>
> +#include <bloblist.h>
>  #include <boot_fit.h>
>  #include <display_options.h>
>  #include <dm.h>
> @@ -87,6 +91,7 @@ static const char *const fdt_src_name[] = {
>         [FDTSRC_BOARD] = "board",
>         [FDTSRC_EMBED] = "embed",
>         [FDTSRC_ENV] = "env",
> +       [FDTSRC_BLOBLIST] = "bloblist",
>  };
>
>  const char *fdtdec_get_srcname(void)
> @@ -1666,20 +1671,35 @@ int fdtdec_setup(void)
>         int ret;
>
>         /* The devicetree is typically appended to U-Boot */
> -       if (IS_ENABLED(CONFIG_OF_SEPARATE)) {
> -               gd->fdt_blob = fdt_find_separate();
> -               gd->fdt_src = FDTSRC_SEPARATE;
> -       } else { /* embed dtb in ELF file for testing / development */
> -               gd->fdt_blob = dtb_dt_embedded();
> -               gd->fdt_src = FDTSRC_EMBED;
> -       }
> -
> -       /* Allow the board to override the fdt address. */
> -       if (IS_ENABLED(CONFIG_OF_BOARD)) {
> -               gd->fdt_blob = board_fdt_blob_setup(&ret);
> +       if (CONFIG_IS_ENABLED(OF_BLOBLIST)) {
> +               ret = bloblist_maybe_init();
>                 if (ret)
>                         return ret;
> -               gd->fdt_src = FDTSRC_BOARD;

So, instead of adding OF_BLOBLIST, just move this code under OF_BOARD,
inside an IS_ENABLED(BLOBLIST) check. If a bloblist is required and
the previous stage loader is supposed to provide a DT we can just
throw an error and stop booting


> +               gd->fdt_blob = bloblist_find(BLOBLISTT_CONTROL_FDT, 0);
> +               if (!gd->fdt_blob) {
> +                       printf("Not FDT found in bloblist\n");
> +                       bloblist_show_list();
> +                       return -ENOENT;
> +               }

[...]

Regards
/Ilias