linux-kernel - Re: [PATCH] dmaengine: Fix return value for dma_requrest

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Message-ID: <3d7a612a-851f-85f1-4207-531f5a87212a@ti.com>
Date:   Wed, 29 Jan 2020 21:51:46 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        <dmaengine@...r.kernel.org>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>, <linux-samsung-soc@...r.kernel.org>
CC:     Mark Brown <broonie@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Vinod Koul <vkoul@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH] dmaengine: Fix return value for dma_requrest_chan() in
 case of failure



On 29/01/2020 18.35, Marek Szyprowski wrote:
> Commit 71723a96b8b1 ("dmaengine: Create symlinks between DMA channels and
> slaves") changed the dma_request_chan() function flow in such a way that
> it always returns EPROBE_DEFER in case of channels that cannot be found.
> This break the operation of the devices which have optional DMA channels
> as it puts their drivers in endless deferred probe loop. Fix this by
> propagating the proper error value.
> 
> Fixes: 71723a96b8b1 ("dmaengine: Create symlinks between DMA channels and slaves")
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>  drivers/dma/dmaengine.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index f3ef4edd4de1..27b64a665347 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -759,7 +759,7 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
>  	if (!IS_ERR_OR_NULL(chan))
>  		goto found;
>  
> -	return ERR_PTR(-EPROBE_DEFER);
> +	return chan;

It should be:
return chan ? chan : ERR_PTR(-EPROBE_DEFER);

dma_request_chan() should never return NULL, it either returns the
dma_chan, or ERR_PTR().

>  
>  found:
>  	chan->slave = dev;
> 

- Péter

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