Re: [PATCH] DMAEngine: Define generic transfer request api

From: Barry Song <21cnbao@gmail.com>
To: Jassi Brar <jaswinder.singh@linaro.org>
Cc: dan.j.williams@intel.com, sundaram@ti.com,
	linus.walleij@linaro.org, vinod.koul@intel.com,
	rmk+kernel@arm.linux.org.uk, linux-omap@vger.kernel.org,
	DL-SHA-WorkGroupLinux <workgroup.linux@csr.com>
Subject: Re: [PATCH] DMAEngine: Define generic transfer request api
Date: Tue, 13 Sep 2011 09:21:54 +0800	[thread overview]
Message-ID: <CAGsJ_4xaDyQgtGZwDjnXn-=ouHzqmVfwaKeDxuouvkPHMkr8mw@mail.gmail.com> (raw)
In-Reply-To: <CAJe_ZhcxEaHoj+6+mTKOk2Jz9KBeTP-M3c2VMn=S4Y-K6iegKw@mail.gmail.com>

2011/9/13 Jassi Brar <jaswinder.singh@linaro.org>:
> On 12 September 2011 21:56, Barry Song <21cnbao@gmail.com> wrote:
>>> Define a new api that could be used for doing fancy data transfers
>>> like interleaved to contiguous copy and vice-versa.
>>> Traditional SG_list based transfers tend to be very inefficient in
>>> such cases as where the interleave and chunk are only a few bytes,
>>> which call for a very condensed api to convey pattern of the transfer.
>>>
>>> This api supports all 4 variants of scatter-gather and contiguous transfer.
>>> Besides, it could also represent common operations like
>>>        device_prep_dma_{cyclic, memset, memcpy}
>>> and maybe some more that I am not sure of.
>>>
>>> Of course, neither can this api help transfers that don't lend to DMA by
>>> nature, i.e, scattered tiny read/writes with no periodic pattern.
>>>
>>> Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
>>
>> anyway, this API needs a real user to prove why it needs to exist.
>>
>> prima2 can be the 1st(?, 2nd if TI uses) user of this API. let's try
>> to see what the driver will be with this api. Then we might figure out
>> more about what it should be.
>>
> Did you discover any issue with the api?

no until now, but i need to test as i said since there is nobody else
has used it before. so i just hold the formal ACK for a moment.

> Because only three days ago you said
> {
> Jassi, you might think my reply as an ACK to "[PATCH] DMAEngine:
> Define generic transfer request api".
> }

if test pass, to the patch, and even for the moment, to the API's idea
Acked-by: Barry Song <baohua.song@csr.com>

>
> The api met your requirements easily not because I know them already,
> but because I designed the api to be as generic as practically possible.
>

-barry
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