linux-kernel - Re: [PATCH] dmaengine: imx-dma: Mark expected switch fall-through

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Message-ID: <201907300958.5F8CC90AD1@keescook>
Date:   Tue, 30 Jul 2019 09:58:31 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: imx-dma: Mark expected switch fall-through

On Mon, Jul 29, 2019 at 05:52:21PM -0500, Gustavo A. R. Silva wrote:
> Mark switch cases where we are expecting to fall through.
> 
> This patch fixes the following warning (Building: arm):
> 
> drivers/dma/imx-dma.c: In function ‘imxdma_xfer_desc’:
> drivers/dma/imx-dma.c:542:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
>    if (slot == IMX_DMA_2D_SLOT_A) {
>       ^
> drivers/dma/imx-dma.c:559:2: note: here
>   case IMXDMA_DESC_MEMCPY:
>   ^~~~
> 
> Notice that, in this particular case, the code comment is
> modified in accordance with what GCC is expecting to find.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/dma/imx-dma.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
> index 00a089e24150..5c0fb3134825 100644
> --- a/drivers/dma/imx-dma.c
> +++ b/drivers/dma/imx-dma.c
> @@ -556,6 +556,7 @@ static int imxdma_xfer_desc(struct imxdma_desc *d)
>  		 * We fall-through here intentionally, since a 2D transfer is
>  		 * similar to MEMCPY just adding the 2D slot configuration.
>  		 */
> +		/* Fall through */
>  	case IMXDMA_DESC_MEMCPY:
>  		imx_dmav1_writel(imxdma, d->src, DMA_SAR(imxdmac->channel));
>  		imx_dmav1_writel(imxdma, d->dest, DMA_DAR(imxdmac->channel));
> -- 
> 2.22.0
> 

-- 
Kees Cook