On 6/18/25 16:59, Raymond Mao wrote:
During FDT setup, apply all existing DT overlays from the bloblist
to the base FDT if bloblist is being used for handoff from previous
boot stage.
More technical details would be good to have here.
Especially that the way what you are using is to expand DT
Signed-off-by: Raymond Mao <raymond....@linaro.org>
---
lib/fdtdec.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 56 insertions(+)
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index c38738b48c7..3a218d8c94a 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -1687,6 +1687,60 @@ void fdtdec_setup_embed(void)
gd->fdt_src = FDTSRC_EMBED;
}
+static int fdtdec_apply_dto_from_blob(void **blob)
+{
+ int ret;
+ struct fdt_header *live_fdt;
+ size_t new_fdt_size, blob_size;
+ int expand_by;
+
+ if (!CONFIG_IS_ENABLED(OF_LIBFDT_OVERLAY) ||
+ !CONFIG_IS_ENABLED(BLOBLIST))
+ return -EPERM;
+
+ live_fdt = bloblist_find(BLOBLISTT_CONTROL_FDT, 0);
+ ret = fdt_check_header(live_fdt);
+ if (ret)
+ return ret;
Why is this needed? You already have gd->fdt_blob which has been checked.
+
+ ret = fdt_check_header(*blob);
+ if (ret)
+ return ret;
+
+ blob_size = fdt_totalsize(*blob);
+
+ /* Expand the FDT for spare spaces to apply the overlay */
+ new_fdt_size = fdt_totalsize(live_fdt) + blob_size + 0x400;
Some notes about this 0x400 would be good. Do you see issue if you don't use
this value? Is file DTB after expansion actually bigger then origin+overlay that
you need to add 0x400 magic value here?
+ ret = bloblist_resize(BLOBLISTT_CONTROL_FDT, new_fdt_size, &expand_by);
+ if (ret)
+ return ret;
You do resize inside tl list.. That should be described in commit message
because my exception was that this location can be read only from NS world.
I didn't run this on HW and likely I should do it to understand this better
but isn't this moving CONTROL_FDT entry to different location which will have
bigger space for applying overlay?
Isn't it also worth to check if existing CONTROL_FDT has enough space inside
that new overlay can fit there before resizing it?
+
+ /* The blob is shifted if it was following the FDT */
+ if (*blob > (void *)live_fdt)
+ *blob += expand_by;
+
+ ret = fdt_open_into(live_fdt, live_fdt, new_fdt_size);
+ if (ret)
+ return ret;
+
+ ret = fdt_overlay_apply_verbose(live_fdt, *blob);
+ if (ret)
+ return ret;
+
+ /* Shrink the excessive spaces */
+ fdt_pack(live_fdt);
+ new_fdt_size = fdt_totalsize(live_fdt);
+ ret = bloblist_resize(BLOBLISTT_CONTROL_FDT, new_fdt_size, &expand_by);
+ if (ret)
+ return ret;
I didn't try to run on HW but don't you need to also adjust gd->fdt_blob to
point to current location where fdt is?
Thanks,
Michal
