Re: loader warnings with LOADER_FDT_SUPPORT

On Sun, Jan 4, 2026 at 6:31 PM Colin Percival <[email protected]> wrote:

> On 1/4/26 17:25, Warner Losh wrote:
> > On Sun, Jan 4, 2026 at 6:16 PM Colin Percival <[email protected]
> > <mailto:[email protected]>> wrote:
> >      > 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?
> >
> > 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
> >
> > ???
>
> Yeah, I was wondering if it was as simple as "if we have ACPI we don't
> need FDT".  (There's two printfs to change though.  If people agree with
> the concept I'll put together a patch, test, and post it for review.)
>

It's complicated by the fact that sometimes you need both (the LinuxBoot
interface requires both). So we have to be careful. We want to warn when we
have NEITHER and I think the above does that. But BOTH is OK, even though
the kernel side of both is still buggy.

Warner