linux-kernel - Re: Buiild error in i915/xe

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Message-ID: <f36700c5-eb86-46c3-afd7-5d3ad67e0130@roeck-us.net>
Date: Sat, 18 Jan 2025 10:36:11 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: David Laight <david.laight.linux@...il.com>
Cc: David Laight <David.Laight@...lab.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 'Arnd Bergmann' <arnd@...nel.org>,
 "'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
 'Jens Axboe' <axboe@...nel.dk>, 'Matthew Wilcox' <willy@...radead.org>,
 'Christoph Hellwig' <hch@...radead.org>,
 'Andrew Morton' <akpm@...ux-foundation.org>,
 'Andy Shevchenko' <andriy.shevchenko@...ux.intel.com>,
 'Dan Carpenter' <dan.carpenter@...aro.org>,
 "'Jason A . Donenfeld'" <Jason@...c4.com>,
 "'pedro.falcato@...il.com'" <pedro.falcato@...il.com>,
 'Mateusz Guzik' <mjguzik@...il.com>,
 "'linux-mm@...ck.org'" <linux-mm@...ck.org>,
 'Lorenzo Stoakes' <lorenzo.stoakes@...cle.com>,
 intel-xe@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: Re: Buiild error in i915/xe

On 1/18/25 10:09, David Laight wrote:
> On Sat, 18 Jan 2025 09:49:21 -0800
> Guenter Roeck <linux@...ck-us.net> wrote:
> 
>> On Sat, Jan 18, 2025 at 05:09:59PM +0000, David Laight wrote:
>>> On Sat, 18 Jan 2025 08:13:06 -0800
>>> Guenter Roeck <linux@...ck-us.net> wrote:
>>>    
>>>> Hi,
>>>>
>>>> On Mon, Nov 18, 2024 at 07:13:31PM +0000, David Laight wrote:
>>>>> Use BUILD_BUG_ON_MSG(statically_true(ulo > uhi), ...) for the sanity
>>>>> check of the bounds in clamp().
>>>>> Gives better error coverage and one less expansion of the arguments.
>>>>>
>>>>> Signed-off-by: David Laight <david.laight@...lab.com>
>>>>
>>>> This patch triggers a build error when trying to build parisc:allmodconfig.
>>>> See error message and bisect log below.
>>>>
>>>> I don't think there is anything wrong with the patch. The underlying
>>>> problem seems to be that parisc:allmodconfig enables CONFIG_DRM_XE which
>>>> tries to build the affected file even though CONFIG_DRM_I915 is not
>>>> enabled/supported on parisc.
>>>
>>> This has appeared before.
>>> Any idea which inlined copy of scale() is causing the problem.
>>> On the face of it they all look ok.
>>>
>>> If you can reproduce it maybe try commenting out some of the calls.
>>>    
>>
>> See diff below. All three changes are needed.
>> No idea why the compiler would know that the values are invalid.
> 
> Maybe it isn't even an inlining issue.
> Perhaps that compiler just doesn't like the function ?
> What happens without the 'static' (and an extra prototype)?
> 

You mean like that ?

-static u32 scale(u32 source_val,
+
+u32 scale(u32 source_val,
+                u32 source_min, u32 source_max,
+                u32 target_min, u32 target_max);
+
+u32 scale(u32 source_val,
                  u32 source_min, u32 source_max,
                  u32 target_min, u32 target_max)

It doesn't help. Worse, after that change the error is still reported
even with the #if 0 elsewhere.

Guenter