linux-kernel - Re: [PATCH v2 1/2] dmaengine: Add support for per xfer specific privatedata & box dma

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Message-ID: <1326808388.1540.123.camel@vkoul-udesk3>
Date:	Tue, 17 Jan 2012 19:23:08 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Ravi Kumar V <kumarrav@...eaurora.org>
Cc:	dan.j.williams@...el.com, arnd@...db.de,
	linux-arch@...r.kernel.org, davidb@...eaurora.org,
	dwalker@...o99.com, bryanh@...eaurora.org, linux@....linux.org.uk,
	tsoni@...lcomm.com, johlstei@...lcomm.com,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] dmaengine: Add support for per xfer specific
 privatedata & box dma

On Fri, 2012-01-06 at 18:17 +0530, Ravi Kumar V wrote:
> Qualcomm MSM have a feature to pass command configuration and
> control data along with source,destination and length of transfer
> for every transaction, as of now struct scatterlist has no support
> to send private data related to each transaction we added private_data
> variable for supporting this type of archictures.
this looks quite similar to what RIO [1] folks were asking, ie ability
to pass specific parameters for each transaction which are device
specific.
> 
> Qualcomm MSM also supports BOX mode of dma, currently as there is no
> API in dmaengine to support this type of dma we added new API.
> 
> Change-Id: Ia9ee19f2c253e68b8e5ff254a57478dcc51014ca
> Signed-off-by: Ravi Kumar V <kumarrav@...eaurora.org>
> ---
>  include/asm-generic/scatterlist.h |    1 +
>  include/linux/dmaengine.h         |   17 ++++++++++++++++-
>  2 files changed, 17 insertions(+), 1 deletions(-)
> 
> diff --git a/include/asm-generic/scatterlist.h b/include/asm-generic/scatterlist.h
> index 5de0735..e66dfcb 100644
> --- a/include/asm-generic/scatterlist.h
> +++ b/include/asm-generic/scatterlist.h
> @@ -14,6 +14,7 @@ struct scatterlist {
>  #ifdef CONFIG_NEED_SG_DMA_LENGTH
>  	unsigned int	dma_length;
>  #endif
> +	unsigned long	private_data;
what do you plan to pass here. Please keep in mind this is a generic
scatterlist structure, and modifying it for your purposes doesn't seem
to be a great one!
Also why can't you pass this as addition argument in your new "BOX API"?

>  };
>  
>  /*
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index 75f53f8..ea29e73 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -72,10 +72,11 @@ enum dma_transaction_type {
>  	DMA_ASYNC_TX,
>  	DMA_SLAVE,
>  	DMA_CYCLIC,
> +	DMA_BOX,
>  };
>  
>  /* last transaction type for creation of the capabilities mask */
> -#define DMA_TX_TYPE_END (DMA_CYCLIC + 1)
> +#define DMA_TX_TYPE_END (DMA_BOX + 1)
>  
> 
>  /**
> @@ -404,6 +405,15 @@ struct dma_tx_state {
>  	u32 residue;
>  };
>  
> +
> +struct dma_box_list {
> +	dma_addr_t dma_row_address;
> +	unsigned int dma_row_len;
> +	unsigned int dma_row_num;
> +	unsigned int dma_row_offset;
> +	unsigned long private_data;
> +};
again a private data here?
is this some kind of interleaved pattern?
> +
>  /**
>   * struct dma_device - info on the entity supplying DMA services
>   * @chancnt: how many DMA channels are supported
> @@ -497,6 +507,11 @@ struct dma_device {
>  	struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)(
>  		struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len,
>  		size_t period_len, enum dma_data_direction direction);
> +	struct dma_async_tx_descriptor *(*device_prep_dma_box)(
> +		struct dma_chan *chan, struct dma_box_list *dst_box,
> +		struct dma_box_list *src_box, unsigned int num_list,
> +		unsigned long flags);
still not clean what kind of transfer do you want to do here
> +
>  	int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
>  		unsigned long arg);
>  


-- 
~Vinod

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