Re: [PATCH v5 9/9] crypto: atmel: Use dmaengine_prep_config_single() API

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Medium] Mismatch between the commit message and the actual API used.
- [Medium] The patch masks specific DMA configuration error codes, unconditionally returning -ENOMEM on failure.
--

commit 05fb1a88b098522438016a4c4b3491605a64cf5f
Author: Frank Li <Frank.Li@nxp.com>

crypto: atmel: Use dmaengine_prep_config_single() API

This commit refactors atmel_aes_dma_transfer_start() to use a new combined
DMA engine API for configuration and scatterlist preparation. The commit
message notes that this is intended to simplify the code with no functional
change.

> crypto: atmel: Use dmaengine_prep_config_single() API
> 
> Using new API dmaengine_prep_config_single() to simple code.

This isn't a bug, but the commit message and subject mention
dmaengine_prep_config_single(), while the code actually introduces and uses
dmaengine_prep_config_sg().

> diff --git a/drivers/crypto/atmel-aes.c b/drivers/crypto/atmel-aes.c
> index b393689400b4c..d890b5a277b9c 100644
> --- a/drivers/crypto/atmel-aes.c
> +++ b/drivers/crypto/atmel-aes.c

[ ... ]

> @@ -820,12 +819,9 @@ static int atmel_aes_dma_transfer_start(struct atmel_aes_dev *dd,
>  		return -EINVAL;
>  	}
>  
> -	err = dmaengine_slave_config(dma->chan, &config);
> -	if (err)
> -		return err;
> -
> -	desc = dmaengine_prep_slave_sg(dma->chan, dma->sg, dma->sg_len, dir,
> -				       DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> +	desc = dmaengine_prep_config_sg(dma->chan, dma->sg, dma->sg_len, dir,
> +					DMA_PREP_INTERRUPT | DMA_CTRL_ACK,
> +					&config);
>  	if (!desc)
>  		return -ENOMEM;

The commit message states there is no functional change, but does this alter
the error propagation?

In the original code, if dmaengine_slave_config() failed, its specific error
code was returned to the caller. Looking at the definition of
dmaengine_prep_config_sg(), it returns NULL if the underlying
dmaengine_slave_config() call fails:

include/linux/dmaengine.h:dmaengine_prep_config_sg() {
        ...
        if (config)
                if (dmaengine_slave_config(chan, config))
                        return NULL;
        ...
}

Since atmel_aes_dma_transfer_start() now handles a NULL return by returning
-ENOMEM, might this mask configuration errors by presenting them as
out-of-memory failures instead of their original error codes?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260512-dma_prep_config-v5-0-26865bf7d935@nxp.com?part=9