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

[Marek Vasut]

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.

> 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.