[PATCHv3 2/6] lmb: add LMB_FDT for fdt reserved regions

[Simon Glass]

Hi Randolph,

On Fri, 17 Apr 2026 at 09:30, Randolph Sapp <rs at ti.com> wrote:
>
> On Thu Apr 16, 2026 at 4:20 PM CDT, Simon Glass wrote:
> > Hi Randolph,
> >
> > On Fri, 17 Apr 2026 at 09:12, Randolph Sapp <rs at ti.com> wrote:
> >>
> >> On Thu Apr 16, 2026 at 4:02 PM CDT, Simon Glass wrote:
> >> > Hi Randolph,
> >> >
> >> > On Tue, 14 Apr 2026 at 08:36, <rs at ti.com> wrote:
> >> >>
> >> >> From: Randolph Sapp <rs at ti.com>
> >> >>
> >> >> Add an LMB_FDT bit for fdt reserved regions, so we can reclaim them when
> >> >> parsing a new device tree and properly warn people when a reservation
> >> >> overlaps with an existing allocation.
> >> >>
> >> >> If we don't at least warn the user of these reservation failures,
> >> >> there's a chance that this region could be freed and reallocated for
> >> >> something important later.
> >> >>
> >> >> This useful warning mechanism was broken in:
> >> >> 5a6aa7d5913 ("boot: fdt: Handle already reserved memory in boot_fdt_reserve_region()")
> >> >>
> >> >> Signed-off-by: Randolph Sapp <rs at ti.com>
> >> >> ---
> >> >>  boot/image-fdt.c |  5 ++++-
> >> >>  include/lmb.h    | 14 ++++++++++++++
> >> >>  lib/lmb.c        | 33 +++++++++++++++++++++++++++++----
> >> >>  3 files changed, 47 insertions(+), 5 deletions(-)
> >> >>
> >> >
> >> > With bootstd we maintain a list of images attached to each bootflow,
> >> > including the address when loaded. Could that provide a solution here?
> >> >
> >> > Regards,
> >> > Simon
> >>
> >> Hey Simon, you may have to elaborate on that a little more. Are you suggesting
> >> we treat FDT reserved regions as dummy bootstd binary entries? That might work
> >> if it counts as an LMB reservation and we can dynamically update it if the FDT
> >> is reloaded/changed. I haven't looked into that too much yet.
> >
> > Not so much dummies, I mean real bootflows. I am not sure if you are
> > using bootstd, though?
> >
> > Basically, once you have a bootflow there is a list of images attached
> > - see struct bootflow_img
> >
> > Each image has a type so you can see if it is an FDT.
> >
> > This is just an idea though...I'm not sure if you are even using bootstd.
> >
> > Regards,
> > Simon
>
> Oh, the issue isn't in the region reserved to load the FDT itself, it's the
> regions the FDT reserves for other components. Specifically the
> "reserved-memory" nodes and other things like that.

OK, got it.

Regards,
Simon