linux-kernel - Re: [PATCH 01/10] dmaengine: add new enum dma_transfer

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Date:	Sat, 15 Oct 2011 13:46:45 +0100
From:	Russell King <rmk@....linux.org.uk>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
	jaswinder.singh@...aro.org, 21cnbao@...il.com,
	Vinod Koul <vinod.koul@...ux.intel.com>
Subject: Re: [PATCH 01/10] dmaengine: add new enum dma_transfer_direction

On Fri, Oct 14, 2011 at 11:08:16AM +0530, Vinod Koul wrote:
> This new enum removes usage of dma_data_direction for dma direction. The new
> enum cleans tells the DMA direction and mode
> This further paves way for merging the dmaengine _prep operations and also for
> interleaved dma
> 
> Suggested-by: Jassi Brar <jaswinder.singh@...aro.org>
> Signed-off-by: Vinod Koul <vinod.koul@...ux.intel.com>
> ---
>  include/linux/dmaengine.h |   22 +++++++++++++++++-----
>  1 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index ace51af..24942ad 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -23,7 +23,6 @@
>  
>  #include <linux/device.h>
>  #include <linux/uio.h>
> -#include <linux/dma-direction.h>
>  #include <linux/scatterlist.h>
>  
>  /**
> @@ -75,6 +74,19 @@ enum dma_transaction_type {
>  /* last transaction type for creation of the capabilities mask */
>  #define DMA_TX_TYPE_END (DMA_CYCLIC + 1)
>  
> +/**
> + * enum dma_transfer_direction - dma transfer mode and direction indicator
> + * @MEM_TO_MEM: Async/Memcpy mode
> + * @MEM_TO_DEV: Slave mode & From Memory to Device
> + * @DEV_TO_MEM: Slave mode & From Device to Memory
> + * @DEV_TO_DEV: Slave mode & From Device to Device
> + */
> +enum dma_transfer_direction {
> +	MEM_TO_MEM,
> +	MEM_TO_DEV,
> +	DEV_TO_MEM,
> +	DEV_TO_DEV,
> +};
>  
>  /**
>   * enum dma_ctrl_flags - DMA flags to augment operation preparation,
> @@ -267,7 +279,7 @@ enum dma_slave_buswidth {
>   * struct, if applicable.
>   */
>  struct dma_slave_config {
> -	enum dma_data_direction direction;
> +	enum dma_transfer_direction direction;

I thought we were killing this off - surely now is a good time, rather
than allowing it to persist with this ambiguous change of functionality.

>  	dma_addr_t src_addr;
>  	dma_addr_t dst_addr;
>  	enum dma_slave_buswidth src_addr_width;
> @@ -490,11 +502,11 @@ struct dma_device {
>  
>  	struct dma_async_tx_descriptor *(*device_prep_slave_sg)(
>  		struct dma_chan *chan, struct scatterlist *sgl,
> -		unsigned int sg_len, enum dma_data_direction direction,
> +		unsigned int sg_len, enum dma_transfer_direction direction,

Does this make any sense?  The API takes a single scatterlist of memory
locations - so MEM_TO_MEM and DEV_TO_DEV are meaningless for this API.

If it took two scatterlists and two device addresses, then maybe it would -
but I don't see the point of this change (and all the users of this API
also needing to change) when the API is specifically for memory scatterlist
to/from a device.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:
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