Re: loader warnings with LOADER_FDT_SUPPORT

On Sun, Jan 4, 2026 at 6:16 PM Colin Percival <[email protected]> wrote:

> Hi all,
>
> The arm64 EFI loader is built with LOADER_FDT_SUPPORT, which is probably
> the
> correct default, but when the loader has LOADER_FDT_SUPPORT set it emits
> some
> unnecessarily scary warnings on many systems:
>
> > No valid device tree blob found!
> > WARNING! Trying to fire up the kernel, but no device tree blob found!
>
> Since many systems legitimately don't have DTBs, can we remove this warning
> and/or make it conditional on some check as to whether we think a DTB might
> be needed?
>
> In particular since this is the last thing the loader prints, it has sent a
> few people down rabbit holes when the serial console in the loader works
> but
> the serial console in the kernel doesn't, since they assume this message is
> somehow related to the lack of further console output.
>

diff --git a/stand/efi/loader/bootinfo.c b/stand/efi/loader/bootinfo.c
index 67b36313c26f..e43eebb4bd5c 100644
--- a/stand/efi/loader/bootinfo.c
+++ b/stand/efi/loader/bootinfo.c
@@ -432,9 +432,12 @@ bi_load(char *args, vm_offset_t *modulep, vm_offset_t
*kernendp, bool exit_bs)
 #if defined(LOADER_FDT_SUPPORT)
        if (dtb_size)
                file_addmetadata(kfp, MODINFOMD_DTBP, sizeof(dtbp), &dtbp);
-       else
-               printf("WARNING! Trying to fire up the kernel, but no "
-                   "device tree blob found!\n");
+       else {
+               if (getenv("acpi.revision") == NULL) {
+                       printf("WARNING! Trying to fire up the kernel, but
no "
+                           "device tree blob found!\n");
+               }
+       }
 #endif
        file_addmetadata(kfp, MODINFOMD_KERNEND, sizeof(kernend), &kernend);
 #ifdef MODINFOMD_MODULEP

???

Warner