linux-kernel - Re: include/linux/compiler_types.h:597:38: error: call to '__compiletime_assert_495' declared with attribute error: FIELD

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Message-ID: <20260123155223.GC415966@killaraus>
Date: Fri, 23 Jan 2026 17:52:23 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Marek Vasut <marek.vasut@...lbox.org>
Cc: kernel test robot <lkp@...el.com>,
	Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>,
	oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: Re: include/linux/compiler_types.h:597:38: error: call to
 '__compiletime_assert_495' declared with attribute error: FIELD_PREP: value
 too large for the field

On Fri, Jan 23, 2026 at 11:15:35AM +0100, Marek Vasut wrote:
> On 1/23/26 1:58 AM, kernel test robot wrote:
> > Hi Marek,
> > 
> > FYI, the error/warning still remains.
> > 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   a66191c590b3b58eaff05d2277971f854772bd5b
> > commit: 4f716a1db661cfb31502a0a6d7e62c06daf2e603 drm/rcar-du: dsi: Convert register bitfields to GENMASK() macro
> > date:   3 months ago
> > config: arc-randconfig-r053-20260123 (https://download.01.org/0day-ci/archive/20260123/202601230809.FBjF6OrH-lkp@intel.com/config)
> > compiler: arc-linux-gcc (GCC) 8.5.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260123/202601230809.FBjF6OrH-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@...el.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202601230809.FBjF6OrH-lkp@intel.com/
> > 
> > All errors (new ones prefixed by >>):
> > 
> >     In file included from <command-line>:
> >     drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c: In function 'rcar_mipi_dsi_startup.isra.6':
> >>> include/linux/compiler_types.h:597:38: error: call to '__compiletime_assert_495' declared with attribute error: FIELD_PREP: value too large for the field
> >       _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> >                                           ^
> >     include/linux/compiler_types.h:578:4: note: in definition of macro '__compiletime_assert'
> >         prefix ## suffix();    \
> >         ^~~~~~
> >     include/linux/compiler_types.h:597:2: note: in expansion of macro '_compiletime_assert'
> >       _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> >       ^~~~~~~~~~~~~~~~~~~
> >     include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
> >      #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> >                                          ^~~~~~~~~~~~~~~~~~
> >     include/linux/bitfield.h:68:3: note: in expansion of macro 'BUILD_BUG_ON_MSG'
> >        BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ?  \
> >        ^~~~~~~~~~~~~~~~
> >     include/linux/bitfield.h:115:3: note: in expansion of macro '__BF_FIELD_CHECK'
> >        __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
> >        ^~~~~~~~~~~~~~~~
> >     drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi_regs.h:259:29: note: in expansion of macro 'FIELD_PREP'
> >      #define VCLKSET_DIV_V4H(n)  FIELD_PREP(VCLKSET_DIV_V4H_MASK, (n))
> >                                  ^~~~~~~~~~
> >     drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c:660:14: note: in expansion of macro 'VCLKSET_DIV_V4H'
> >        vclkset |= VCLKSET_DIV_V4H(__ffs(setup_info.vclk_divider) - 1);
> >                   ^~~~~~~~~~~~~~~
> 
> Hello Tomi, Laurent,
> 
> maybe it would be good to pick:
> 
> drm/rcar-du: dsi: Clean up VCLK divider calculation
> 
> that was posted about a month ago and fixes this exact warning ?

About half a month actually. I've reviewed the patch (thanks for the
ping) and asked Tomi to push it.

-- 
Regards,

Laurent Pinchart