[PATCH v2 2/3] riscv: Expand the DT size before copy reserved memory node

[Bin Meng]

Hi Atish,

On Wed, Jun 3, 2020 at 2:23 AM Atish Patra <atishp at atishpatra.org> wrote:
>
> On Thu, May 28, 2020 at 1:47 AM Bin Meng <bmeng.cn at gmail.com> wrote:
> >
> > From: Bin Meng <bin.meng at windriver.com>
> >
> > The FDT blob might not have sufficient space to hold a copy of
> > reserved memory node. Expand it before the copy.
> >
> > Reported-by: Rick Chen <rick at andestech.com>
> > Signed-off-by: Bin Meng <bin.meng at windriver.com>
> > ---
> >
> >  arch/riscv/lib/fdt_fixup.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/riscv/lib/fdt_fixup.c b/arch/riscv/lib/fdt_fixup.c
> > index 5f523f0..1290a64 100644
> > --- a/arch/riscv/lib/fdt_fixup.c
> > +++ b/arch/riscv/lib/fdt_fixup.c
> > @@ -41,6 +41,12 @@ int riscv_fdt_copy_resv_mem_node(const void *src, void *dst)
> >                 return 0;
> >         }
> >
> > +       err = fdt_open_into(dst, dst, fdt_totalsize(dst) + 32);
>
> The size may be bigger than 32 bytes in future given that we may have
> multiple reserved pmp regions.
> How about calculating the size from the source and using that instead
> of a fixed size ?
>

This looks way too complicated. That means the codes here need to
understand the FDT blob binary representation to know exactly how much
additional size is needed. By looking at existing calls to
fdt_open_into() none of these do such things.

I guess we will have to give an estimated size to fit all possible
situations. Say there are 16 PMP regions, and one occupies 64 bytes,
so we can extend the FDT by 64 * 16 = 1024 bytes. Thoughts ??

>
> > +       if (err < 0) {
> > +               printf("Device Tree can't be expanded to accommodate new node");
> > +               return err;
> > +       }
> > +
> >         fdt_for_each_subnode(node, src, offset) {
> >                 name = fdt_get_name(src, node, NULL);
> >

Regards,
Bin