Buiild error in i915/xe

[Guenter Roeck]

On 1/20/25 11:14, Linus Torvalds wrote:
> On Mon, 20 Jan 2025 at 10:55, Andy Shevchenko
> <andriy.shevchenko at linux.intel.com> wrote:
>>
>> Excuse me if I am missing something, but clamp() has a warning inside it, correct?
>> Why do we need an additional warning on top of that?
> 
> Note: the warning in clamp() only finds compile-time obvious wrong uses.
> 
> It's really meant to notice the trivial case where you clam with
> constants and just got the order wrong, so you do something silly like
> 
>      res = clamp(in, 15, 1);
> 
> but it does also end up catching slightly more complex things where
> the compiler can figure out the range of the clamping.
> 
> The build problem then comes from the compiler doing various *other*
> code movem,ent and optimization too, and - like in this case - finds
> an error path where the clamping is done "wrong".
> 
> I think the real issue in the i915 driver is that it does that
> WARN_ON(), but then it just happily continues anyway.
> 
> So if the i915 driver instead did
> 
>          if (WARN_ON(..)) return invalid value;
> 
> none of this would ever have happened.
> 

I'll take a stab and send a patch combining your and David's suggestions.

Guenter