# Re: \[PATCH\] dmaengine: dmaengine\_desc\_callback\_valid(): Check for \`callback\_result\`

- From: Dave Jiang \<dave.jiang@intel.com\>
- Date: 2021-10-24 18:19:46 
- List: dmaengine
- Page: https://ratatoskr.run/dmaengine/2021/10/11792149
- Thread: https://ratatoskr.run/dmaengine/2021/10/11792148/t.md

```text

On 10/23/2021 6:41 AM, Lars-Peter Clausen wrote:
> Before the `callback_result` callback was introduced drivers coded their
> invocation to the callback in a similar way to:
>
> 	if (cb->callback) {
> 		spin_unlock(&dma->lock);
> 		cb->callback(cb->callback_param);
> 		spin_lock(&dma->lock);
> 	}
>
> With the introduction of `callback_result` two helpers where introduced to
> transparently handle both types of callbacks. And drivers where updated to
> look like this:
>
> 	if (dmaengine_desc_callback_valid(cb)) {
> 		spin_unlock(&dma->lock);
> 		dmaengine_desc_callback_invoke(cb, ...);
> 		spin_lock(&dma->lock);
> 	}
>
> dmaengine_desc_callback_invoke() correctly handles both `callback_result`
> and `callback`. But we forgot to update the dmaengine_desc_callback_valid()
> function to check for `callback_result`. As a result DMA descriptors that
> use the `callback_result` rather than `callback` don't have their callback
> invoked by drivers that follow the pattern above.
>
> Fix this by checking for both `callback` and `callback_result` in
> dmaengine_desc_callback_valid().
>
> Fixes: f067025bc676 ("dmaengine: add support to provide error result from a DMA transation")
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

Acked-by: Dave Jiang <dave.jiang@intel.com>


> ---
>   drivers/dma/dmaengine.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dma/dmaengine.h b/drivers/dma/dmaengine.h
> index 1bfbd64b1371..53f16d3f0029 100644
> --- a/drivers/dma/dmaengine.h
> +++ b/drivers/dma/dmaengine.h
> @@ -176,7 +176,7 @@ dmaengine_desc_get_callback_invoke(struct dma_async_tx_descriptor *tx,
>   static inline bool
>   dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
>   {
> -	return (cb->callback) ? true : false;
> +	return cb->callback || cb->callback_result;
>   }
>   
>   struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
```