linux-kernel - Re: [PATCH 2/8] dmaengine: Add flow controller information to dma_slave

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Message-ID: <4F16A1B3.5000409@st.com>
Date:	Wed, 18 Jan 2012 16:10:51 +0530
From:	Viresh Kumar <viresh.kumar@...com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	"vinod.koul@...el.com" <vinod.koul@...el.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Armando VISCONTI <armando.visconti@...com>,
	Shiraz HASHIM <shiraz.hashim@...com>,
	Vipin KUMAR <vipin.kumar@...com>,
	Rajeev KUMAR <rajeev-dlh.kumar@...com>,
	Deepak SIKRI <deepak.sikri@...com>,
	Vipul Kumar SAMAR <vipulkumar.samar@...com>,
	Amit VIRDI <Amit.VIRDI@...com>,
	Pratyush ANAND <pratyush.anand@...com>,
	Bhupesh SHARMA <bhupesh.sharma@...com>,
	"viresh.linux@...il.com" <viresh.linux@...il.com>,
	Bhavna YADAV <bhavna.yadav@...com>,
	Vincenzo FRASCINO <Vincenzo.FRASCINO@...com>,
	Mirko GARDI <mirko.gardi@...com>
Subject: Re: [PATCH 2/8] dmaengine: Add flow controller information to dma_slave_config

On 1/18/2012 4:06 PM, Linus Walleij wrote:
> On Tue, Jan 17, 2012 at 10:07 AM, Viresh Kumar <viresh.kumar@...com> wrote:
>> On 1/17/2012 2:07 PM, Linus Walleij wrote:

> Maybe I should say that it's supposed to transfer information from
> the driver to the DMA engine that:
> 
> 1) The driver naturally "knows", like which physical register address
>   the FIFO is in or burst width etc and the DMA engine has no
>   business knowing.
> 
> 2) That needs to change at runtime, like for example how the PL022
>  driver request 32, 16 or 8 bit wide transfers depending on bus
>  width.
> 
> I think master mode could very well be under (1). So the driver knows
> if this hardware expects the DMA engine to drive the transaction or
> if it's the device itself that should drive it.
> 
> So I'm starting to think like you :-)

:)

>> One more thing. I missed few things in this patch:
>> - Need to update all instances of struct dma_slave_config with
>>        .device_fc = false
> 
> All statically defined structs contain zero == false by default
> so it's not needed.
> 
> Make sure any dynamic allocations (I don't know of any!)
> are kzalloc() though.
> 

I already fixed these in V2.
Most of the drivers created inside routines. They are not getting
initialized to _zero_ , so i had to fix it.

There are few though, who used kzalloc. I didn't touch them.

-- 
viresh
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