Re: [PATCH] nfp: convert nfp_eth_set_bit_config() into a macro

From: Manoj Gupta
Date: Wed Oct 04 2017 - 20:38:42 EST

Hi Jakub,

On Wed, Oct 4, 2017 at 4:25 PM, Jakub Kicinski
<jakub.kicinski@xxxxxxxxxxxxx> wrote:
> On Wed, 4 Oct 2017 16:16:49 -0700, Matthias Kaehlcke wrote:
>> > > Thanks for the suggestion. This seems a viable alternative if David
>> > > and the NFP owners can live without the extra checking provided by
>> > > __BF_FIELD_CHECK.
>> >
>> > The reason the __BF_FIELD_CHECK refuses to compile non-constant masks
>> > is that it will require runtime ffs on the mask, which is potentially
>> > costly. I would also feel quite stupid adding those macros to the nfp
>> > driver, given that I specifically created the bitfield.h header to not
>> > have to reimplement these in every driver I write/maintain.
>> That make sense, thanks for providing more context.
>> > Can you please test the patch I provided in the other reply?
>> With this patch there are no errors when building the kernel with
>> clang.
> Cool, thanks for checking! I will run it through full tests and queue
> for upstreaming :)

Just to let you know, using __BF_FIELD_CHECK macro will not Link with
-O0 (GCC or Clang) since references to __compiletime_assert_xxx will
not be cleaned up.