RE: [PATCH net v3 1/3] rtase: Modify the condition used to detect overflow in rtase_calc_time_mitigation

[Justin Lai <justinlai0215@realtek.com>]

> On Thu, Apr 17, 2025 at 04:56:57PM +0800, Justin Lai wrote:
> > Fix the following compile error reported by the kernel test robot by
> > modifying the condition used to detect overflow in
> > rtase_calc_time_mitigation.
> >
> > In file included from include/linux/mdio.h:10:0,
> >                   from
> drivers/net/ethernet/realtek/rtase/rtase_main.c:58:
> >  In function 'u16_encode_bits',
> >      inlined from 'rtase_calc_time_mitigation.constprop' at drivers/net/
> >      ethernet/realtek/rtase/rtase_main.c:1915:13,
> >      inlined from 'rtase_init_software_variable.isra.41' at drivers/net/
> >      ethernet/realtek/rtase/rtase_main.c:1961:13,
> >      inlined from 'rtase_init_one' at drivers/net/ethernet/realtek/
> >      rtase/rtase_main.c:2111:2:
> > >> include/linux/bitfield.h:178:3: error: call to '__field_overflow'
> >       declared with attribute error: value doesn't fit into mask
> >     __field_overflow();     \
> >     ^~~~~~~~~~~~~~~~~~
> >  include/linux/bitfield.h:198:2: note: in expansion of macro
> > '____MAKE_OP'
> >    ____MAKE_OP(u##size,u##size,,)
> >    ^~~~~~~~~~~
> >  include/linux/bitfield.h:200:1: note: in expansion of macro
> > '__MAKE_OP'
> >   __MAKE_OP(16)
> >   ^~~~~~~~~
> >
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes:
> > https://lore.kernel.org/oe-kbuild-all/202503182158.nkAlbJWX-lkp@intel.
> > com/
> > Fixes: a36e9f5cfe9e ("rtase: Add support for a pci table in this
> > module")
> > Signed-off-by: Justin Lai <justinlai0215@realtek.com>
> 
> Hi Justin,
> 
> FWIIW, I note that this problem is reported by GCC 7.5.0 on sparc64 but not by
> GCC 14.2.0. And I think that is because in the end the values passed to
> u16_encode_bits (line 1915 in the trace above) are the same with and without
> this patch. That is to say, this the compiler error above is a false positive of
> sorts.
> 
> But I believe GCC 7.5.0 is a supported compiler version for sparc64.
> And this does result in an error, without W=1 or any other extra KCFLAGS set.
> So I agree this is appropriate to treat as a fix for net.
> 
> And in any case, fix or no fix, it seems nice to limit the scope of the
> initialisation of msb.
> 
> Reviewed-by: Simon Horman <horms@kernel.org>

Hi Simon,

Thank you for your review. I will repost this patch separately in the
net tree.

Thanks,
Justin