linux-kernel - Re: [RFC 1/6] bidi support: request dma_data

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Date:	Mon, 22 Jan 2007 07:29:39 +0200
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	Jens Axboe <jens.axboe@...cle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Mike Christie <michaelc@...wisc.edu>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	open-iscsi@...glegroups.com, Daniel.E.Messinger@...gate.com,
	Liran Schour <LIRANS@...ibm.com>,
	Benny Halevy <bhalevy@...asas.com>
Subject: Re: [RFC 1/6] bidi support: request dma_data_direction

On Mon, Jan 22, 2007 at 01:21:28AM +0200, Boaz Harrosh wrote:

> - Introduce a new enum dma_data_direction data_dir member in struct request.
>   and remove the RW bit from request->cmd_flag

Some architecture use 'enum dma_data_direction' and some 'int
dma_data_direction'. The consensus was to move to int over
time. Please use 'int dma_data_direction'.

> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index ff203c4..abbca7b 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -13,6 +13,28 @@ enum dma_data_direction {
>  	DMA_NONE = 3,
>  };
> 
> +static inline int dma_write_dir(enum dma_data_direction dir)
> +{
> +	return (dir == DMA_TO_DEVICE) || (dir == DMA_BIDIRECTIONAL);
> +}

"write" can mean "write to device" or "write to memory", depending on
context. Not exactly something which should be a generic
helper. Rename to 'dma_to_device(int dir)'?

> +static inline int dma_uni_dir(enum dma_data_direction dir)
> +{
> +	return (dir == DMA_TO_DEVICE) || (dir == DMA_FROM_DEVICE) ||
> +	       (dir == DMA_NONE);
> +}

While this doesn't look very useful. Why is "DMA_NONE" a uni-dir? I
suggest replacing this with an open coded (dir != DMA_BIDIRECTIONAL).

Cheers,
Muli
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