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Date:	Thu, 03 Jul 2008 18:23:13 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Subrahmanyam Bolla <sbolla@...c.com>
Cc:	linux-kernel@...r.kernel.org,
	"Sosnowski, Maciej" <maciej.sosnowski@...el.com>,
	Tushar Tyagi <ttyagi@...c.com>, Loc Ho <lho@...c.com>
Subject: Re: Extending Linux async_tx interface


On Mon, 2008-06-23 at 16:07 -0700, Subrahmanyam Bolla wrote:
> Hi,
> 
> I'm working on a new DMA driver for our hardware that supports various
> modes of operations like memory to memory, memory to custom format, and
> visa-versa.
> The current Linux async_tx DMA interface only supports memory to memory
> transfer. We would like to extend this interface to support our
> hardware's new capabilities.
> 
> Other than async_memcpy and async_memset operations supported by linux
> async_tx interface, we would like to add something like
> async_mem_buff_cpy,
> async_pkt_mem_cpy and a few more. These new operations use a new format
> for specifying the source and/or destination for doing the transfer.
> To support this we will have new structures as the API parameters.
> 
> Could you pls let me know if this is the right approach or if there are
> any other suggestions.
> 
It is difficult to know if this is the right approach without knowing
more about the intended usage.  For example async_tx is meant for code
paths where it does not matter if an offload engine is available.
Compare that to Haavard's dma-slave implementation where the driver is
explicitly using a specific dma channel[1].  Which approach better fits
what you are trying to accomplish?

--
Dan

[1] http://marc.info/?l=linux-kernel&m=121448921821512&w=2



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