linux-kernel - Re: [PATCH v3 1/2] i2c: add DMA support for freescale i2c driver

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Date:	Wed, 26 Mar 2014 07:26:36 +0100
From:	Marek Vasut <marex@...x.de>
To:	Yao Yuan <yao.yuan@...escale.com>
Cc:	"wsa@...-dreams.de" <wsa@...-dreams.de>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] i2c: add DMA support for freescale i2c driver

On Wednesday, March 26, 2014 at 06:56:34 AM, Yao Yuan wrote:
> On Wednesday, March 26, 2014 at 11:43:27 AM, Marek Vasut wrote:
> > On Wednesday, March 26, 2014 at 04:08:27 AM, Yao Yuan wrote:
> > 
> > [...]
> > 
> > > > > +		i2c_imx->use_dma = false;
> > > > > +	} else if (i2c_imx_dma_request(i2c_imx, (dma_addr_t)phy_addr))
> > 
> > {
> > 
> > > > > +		dev_info(&pdev->dev,
> > > > > +				"can't request dma chan, faild use dma.
\n");
> > > > > +		i2c_imx->use_dma = false;
> > > > > +	} else {
> > > > > +		i2c_imx->use_dma = true;
> > > > > +	}
> > > > 
> > > > Can you not just check if i2c_imx->dma is valid pointer or NULL
> > 
> > pointer ?
> > 
> > > > Then you won't need a separate variable, for this purpose ... right ?
> > > 
> > > Sorry and I think what I know is just to check whether it is NULL.
> > > Then for the second question, maybe there are some other ways, But I
> > > think it is more tidy and easier understanding for using a separate
> > > variable, for this purpose.
> > 
> > You are just wasting space and duplicating data, unless I am wrong.
> 
> Well, Do you have a better idea? Although I think it's necessary.

I think we disconnected here, sorry. Why can you not use (i2c_imx->dma != NULL) 
instead of (i2c_imx->use_dma == true) please ?

Best regards,
Marek Vasut
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