[PATCH] i2c: sandbox: Avoid calling dev_read_*() if CONFIG_OF_PLATDATA=y

[Simon Glass]

Hi Marek,

On Fri, 21 Nov 2025 at 10:34, Marek Vasut <marek.vasut at mailbox.org> wrote:
>
> On 11/21/25 5:20 PM, Simon Glass wrote:
>
> Hello Simon,
>
> >>> - create a new VALID_OFFSET assumption (split out from VALID_DTB)
> >>> which checks offsets in fdt_next_tag()
> >>>
> >>> The latter might be best. It would likely be very cheap in terms of
> >>> code size. In fact, I should have thought of this at the time.
> >> Wouldn't it be better to not misuse libfdt ?
> >
> > It actually isn't a misuse. It is perfectly OK to pass an invalid
> > offset and libfdt has defined behaviour in that case, absent any
> > 'assumptions' we force.
>
> It actually isn't OK to pass in invalid offset if we compile FDT with
> disabled tree validity checks.

We are saying exactly the same thing, if you read both of the above :-)

>
> > Remember, in Linux these checks are enabled. We added the 'assume'
> > thing to reduce code size. Here you have found a situation where it
> > breaks stuff, so we should back off the assumption a bit.
> U-Boot also has those checks enabled, SPL does not, and things break
> when OF_PLATDATA is enabled and there is no valid node associated with
> the udevice.

Right, so add SPL_OF_LIBFDT_ASSUME_MASK for SPL and check the code
size. If it is too much, add a new level FDT_ASSUME_EXISTS before
FDT_ASSUME_SANE and use that for the necessary checks (there will only
be a few, from my reading of the code).

REgards,
Simon