linux-kernel - Re: [PATCH v2] spi: spi-ep93xx: Change dir type in ep93xx_spi_dma

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Date:   Thu, 4 Oct 2018 14:32:48 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     broonie@...nel.org, linux-spi@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] spi: spi-ep93xx: Change dir type in ep93xx_spi_dma_{finish,prepare}

On Wed, Oct 3, 2018 at 7:41 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang warns when one enumerated type is implicitly converted to another.
>
> drivers/spi/spi-ep93xx.c:342:62: warning: implicit conversion from
> enumeration type 'enum dma_transfer_direction' to different enumeration
> type 'enum dma_data_direction' [-Wenum-conversion]

I'm just trying to think what this change would look like if this
driver ONLY used `enum dma_data_direction`?  There's an additional
warning in the header that a return value is messed up there, too:

In file included from drivers/spi/spi-ep93xx.c:34:
./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;
                ~~~~~~ ^~~~~~~~

>         nents = dma_map_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
>                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
> ./include/linux/dma-mapping.h:428:58: note: expanded from macro
> 'dma_map_sg'
> #define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, 0)
>                                ~~~~~~~~~~~~~~~~          ^
> drivers/spi/spi-ep93xx.c:348:57: warning: implicit conversion from
> enumeration type 'enum dma_transfer_direction' to different enumeration
> type 'enum dma_data_direction' [-Wenum-conversion]
>                 dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
>                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
> ./include/linux/dma-mapping.h:429:62: note: expanded from macro
> 'dma_unmap_sg'
> #define dma_unmap_sg(d, s, n, r) dma_unmap_sg_attrs(d, s, n, r, 0)
>                                  ~~~~~~~~~~~~~~~~~~          ^
> drivers/spi/spi-ep93xx.c:377:56: warning: implicit conversion from
> enumeration type 'enum dma_transfer_direction' to different enumeration
> type 'enum dma_data_direction' [-Wenum-conversion]
>         dma_unmap_sg(chan->device->dev, sgt->sgl, sgt->nents, dir);
>         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~
> ./include/linux/dma-mapping.h:429:62: note: expanded from macro
> 'dma_unmap_sg'
> #define dma_unmap_sg(d, s, n, r) dma_unmap_sg_attrs(d, s, n, r, 0)
>                                  ~~~~~~~~~~~~~~~~~~          ^
> 3 warnings generated.
>
> dma_{,un}map_sg expects an enum of type dma_data_direction but this
> driver uses dma_transfer_direction for everything. Converting to
> dma_data_direction would be desirable but there are a few shared
> structures that expect dma_transfer_direction so it is just simpler to
> change the parameter here. dma_transfer_direction and dma_data_direction
> are different sizes but this driver only uses the 1 and 2 values which
> mean the same thing so this change is safe.
>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>
> v1 -> v2:
>
> * Fix escaped hash symbols for '#define' lines
>
>  drivers/spi/spi-ep93xx.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/spi/spi-ep93xx.c b/drivers/spi/spi-ep93xx.c
> index f1526757aaf6..189fc2225b69 100644
> --- a/drivers/spi/spi-ep93xx.c
> +++ b/drivers/spi/spi-ep93xx.c
> @@ -256,8 +256,7 @@ static int ep93xx_spi_read_write(struct spi_master *master)
>   * in case of failure.
>   */
>  static struct dma_async_tx_descriptor *
> -ep93xx_spi_dma_prepare(struct spi_master *master,
> -                      enum dma_transfer_direction dir)
> +ep93xx_spi_dma_prepare(struct spi_master *master, int dir)
>  {
>         struct ep93xx_spi *espi = spi_master_get_devdata(master);
>         struct spi_transfer *xfer = master->cur_msg->state;
> @@ -359,8 +358,7 @@ ep93xx_spi_dma_prepare(struct spi_master *master,
>   * Function finishes with the DMA transfer. After this, the DMA buffer is
>   * unmapped.
>   */
> -static void ep93xx_spi_dma_finish(struct spi_master *master,
> -                                 enum dma_transfer_direction dir)
> +static void ep93xx_spi_dma_finish(struct spi_master *master, int dir)
>  {
>         struct ep93xx_spi *espi = spi_master_get_devdata(master);
>         struct dma_chan *chan;
> --
> 2.19.0
>


-- 
Thanks,
~Nick Desaulniers