Messages in this thread | | | From | Nick Desaulniers <> | Date | Wed, 12 Sep 2018 10:00:57 -0700 | Subject | Re: [PATCH] dmaengine: ep93xx: Return proper enum in ep93xx_dma_chan_direction |
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On Tue, Sep 11, 2018 at 4:40 PM Nathan Chancellor <natechancellor@gmail.com> wrote: > > Clang warns when implicitly converting from one enumerated type to > another. Avoid this by using the equivalent value from the expected > type. > > In file included from drivers/dma/ep93xx_dma.c:30: > ./include/linux/platform_data/dma-ep93xx.h:88:10: warning: implicit > conversion from enumeration type 'enum dma_data_direction' to different > enumeration type 'enum dma_transfer_direction' [-Wenum-conversion] > return DMA_NONE; > ~~~~~~ ^~~~~~~~ > 1 warning generated. > > Reported-by: Nick Desaulniers <ndesaulniers@google.com> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > --- > include/linux/platform_data/dma-ep93xx.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/platform_data/dma-ep93xx.h b/include/linux/platform_data/dma-ep93xx.h > index f8f1f6b952a6..eb9805bb3fe8 100644 > --- a/include/linux/platform_data/dma-ep93xx.h > +++ b/include/linux/platform_data/dma-ep93xx.h > @@ -85,7 +85,7 @@ static inline enum dma_transfer_direction > ep93xx_dma_chan_direction(struct dma_chan *chan) > { > if (!ep93xx_dma_chan_is_m2p(chan)) > - return DMA_NONE; > + return DMA_TRANS_NONE;
Looks like this changes the value of the returned enum from: DMA_NONE: 3 DMA_TRANS_NONE: 4
Hopefully the DMA maintainer can review if this was ever correct? Looks like the callers of ep93xx_dma_chan_direction were comparing this return type, so those comparisons would likely always be failing if `!ep93xx_dma_chan_is_m2p(chan)`.
Normally this warning (-Wenum-conversion) is kind of noisey, but it's concerning when the enumerated values evaluate to different integers. I think it's found an actual bug here. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > /* even channels are for TX, odd for RX */ > return (chan->chan_id % 2 == 0) ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM; > -- > 2.18.0 >
-- Thanks, ~Nick Desaulniers
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