Messages in this thread | | | Date | Thu, 17 Sep 2020 07:24:00 +0200 | From | Greg KH <> | Subject | Re: [PATCH] bitfield.h: annotate type_replace_bits functions with __must_check |
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On Thu, Sep 17, 2020 at 09:34:59AM +0530, Vinod Koul wrote: > On 16-09-20, 16:33, Srinivas Kandagatla wrote: > > > > > > On 16/09/2020 16:20, Greg KH wrote: > > > On Wed, Sep 16, 2020 at 04:03:33PM +0100, Srinivas Kandagatla wrote: > > > > usage of apis like u32_replace_bits() without actually catching the return > > > > value could hide problems without any warning! > > > > > > > > Found this with recent usage of this api in SoundWire! > > > > Having __must_check annotation would really catch this issues in future! > > > > > > > > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> > > > > --- > > > > include/linux/bitfield.h | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h > > > > index 4e035aca6f7e..eb4f69253946 100644 > > > > --- a/include/linux/bitfield.h > > > > +++ b/include/linux/bitfield.h > > > > @@ -131,7 +131,7 @@ static __always_inline __##type type##_encode_bits(base v, base field) \ > > > > __field_overflow(); \ > > > > return to((v & field_mask(field)) * field_multiplier(field)); \ > > > > } \ > > > > -static __always_inline __##type type##_replace_bits(__##type old, \ > > > > +static __always_inline __must_check __##type type##_replace_bits(__##type old, \ > > > > base val, base field) \ > > > > { \ > > > > return (old & ~to(field)) | type##_encode_bits(val, field); \ > > > > -- > > > > 2.21.0 > > > > > > > > > > Don't add __must_check to things that if merged will instantly cause > > > build warnings to the system, that's just rude :( > > Currently there are not many users for this api, found only one instance in > > drivers/net/ipa/ipa_table.c which is also fixed with > > https://lkml.org/lkml/2020/9/10/1062 > > > > > > > > Fix up everything first, and then try to make this type of change. > > > > > > But why does this function have to be checked? > > As this function would return updated value, this check is more to with > > using the return value! > > > > It is easy for someone to ignore this return value assuming that the new > > value is already updated! So this check should help! > > > > TBH, This is what happened when we(vkoul and me) tried use this api :-) > > So the only user of this has been moved to *p_replace_bits(), looking > back I think we should remove *_replace_bits (no users atm) and > duplicate of *p_replace_bits(). If not adding this patch would be > sensible thing to do > > Somehow I feel former is a better idea ;-)
Yes, please remove it if there is no users.
thanks,
greg k-h
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