Re: [linux-next:master 1418/1780] kismet: WARNING: unmet direct dependencies detected for FB_DEFERRED_IO when selected by FB_DMAMEM_HELPERS_DEFERRED

[Philip Li <philip.li@intel.com>]

On Fri, Feb 07, 2025 at 11:59:58AM +0000, Lorenzo Stoakes wrote:
> On Fri, Feb 07, 2025 at 03:24:13AM +0800, kernel test robot wrote:
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   808eb958781e4ebb6e9c0962af2e856767e20f45
> > commit: 236ee083f1b9128fd5bd266054c5b8868f803cee [1418/1780] fbdev: have CONFIG_FB_DEFERRED_IO depend on CONFIG_MMU
> > config: arm-kismet-CONFIG_FB_DEFERRED_IO-CONFIG_FB_DMAMEM_HELPERS_DEFERRED-0-0 (https://download.01.org/0day-ci/archive/20250207/202502070305.1rGTDnW0-lkp@intel.com/config)
> 
> I'm not really sure what a kismet device is or how it's configured or where
> on earth this comes from?
> 
> Could somebody on intel test side please clarify? Because you might just
> have a broken config here?

Hi Lorenzo, kismet is part of kmax [1] by Paul Gazzillo, which checks for unmet
dependency bugs in Kconfig specifications due to reverse dependencies overriding
direct dependencies.

The 0day bot had used it to detect possible dependency issues [2]. And the issue
can also be reproduced by running "make ARCH=arm olddefconfig" on the attached
.config.

Would you mind check again whether the generated .config is a valid one that
exposes potential issue?

[1] https://github.com/paulgazz/kmax#using-kismet
[2] https://lore.kernel.org/oe-kbuild-all/?q=kismet
[3] https://download.01.org/0day-ci/archive/20250207/202502070305.1rGTDnW0-lkp@intel.com/reproduce

> 
> Thanks!
> 
> > reproduce: (https://download.01.org/0day-ci/archive/20250207/202502070305.1rGTDnW0-lkp@intel.com/reproduce)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202502070305.1rGTDnW0-lkp@intel.com/
> >
> > kismet warnings: (new ones prefixed by >>)
> > >> kismet: WARNING: unmet direct dependencies detected for FB_DEFERRED_IO when selected by FB_DMAMEM_HELPERS_DEFERRED
> >    WARNING: unmet direct dependencies detected for FB_DEFERRED_IO
> >      Depends on [n]: HAS_IOMEM [=y] && FB_CORE [=y] && MMU [=n]
> >      Selected by [y]:
> >      - FB_DMAMEM_HELPERS_DEFERRED [=y] && HAS_IOMEM [=y] && FB_CORE [=y]
> 
> This is a nommu device selecting a feature that absolutely requires an
> mmu. Something's broken here.
> 
> I'm not sure pretending an mmu-dependent feature is does not rely on the
> mmu is the way to fix this.
> 
> I'm VERY reluctant to add a stub for the function that explicitly relies on
> CONFIG_MMU because it'd be very misleading.
> 
> 
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://github.com/intel/lkp-tests/wiki
>