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

[Tom Rini]

On Fri, Nov 21, 2025 at 10:40:13AM -0700, Simon Glass wrote:
> 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).

We already have different mask values for each xPL and then full U-Boot.
It doesn't seem like there is a good reason to allow this behavior in
xPL is the problem.

-- 
Tom
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