[PATCHv6 1/3] sandbox: add board_get_usable_ram_top

[Simon Glass]

Hi Randolph,

On 2026-05-08T22:29:09, Randolph Sapp <rs at ti.com> wrote:
> sandbox: add board_get_usable_ram_top
>
> Add a board_get_usable_ram_top definition, since currently ram_top is
> equal to ram_size. Attempting to actually map ram_size with map_sysmem
> results in a fault.
>
> Signed-off-by: Randolph Sapp <rs at ti.com>
>
> board/sandbox/sandbox.c | 5 +++++
>  1 file changed, 5 insertions(+)

> diff --git a/board/sandbox/sandbox.c b/board/sandbox/sandbox.c
> @@ -105,6 +105,11 @@ int dram_init(void)
> +phys_addr_t board_get_usable_ram_top(phys_size_t total_size)
> +{
> +     return gd->ram_size - 1;
> +}
> +

Please describe which caller actually faults on map_sysmem(), since
that is the real motivation.

But this contradicts the documented API. From include/init.h:

   The returned address is exclusive (i.e. 1 byte above the
   last usable address).

See the weak function in common/board_f.c

If the real problem is callers doing map_sysmem(ram_top, ...) and
faulting, you could fix it in those callers (use ram_top - 1 when you
need the last valid byte). But I could take a look if you point to the
code.

Also, this uses gd->ram_size as if it were an address; it should
really be gd->ram_base + gd->ram_size. It happens to work because
sandbox's ram_base is 0, but it reads as a type confusion.

Regards,
Simon