[PATCH] dmaengine: Fix return value for dma_requrest_chan() in case of failure

[PATCH] dmaengine: Fix return value for dma_requrest_chan() in case of failure

[Marek Szyprowski]

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@samsung.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;
 
 found:
 	chan->slave = dev;
-- 
2.17.1

Re: [PATCH] dmaengine: Fix return value for dma_requrest_chan() in case of failure

[Peter Ujfalusi]

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@samsung.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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