Date: Thu, 3 Apr 2014 15:37:03 +0800
From: Shawn Guo <shawn.guo@linaro.org>
To: Marek Vasut <marex@denx.de>
CC: Yao Yuan <yao.yuan@freescale.com>, "wsa@the-dreams.de" <wsa@the-dreams.de>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        "linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>
Subject: Re: [PATCH v3 1/2] i2c: add DMA support for freescale i2c driver
Message-ID: <20140403073701.GL2801@dragon>
References: <1394675277-24913-1-git-send-email-yao.yuan@freescale.com>
 <201403260726.36812.marex@denx.de>
 <8984936f9e914442995d79039543cb58@BL2PR03MB338.namprd03.prod.outlook.com>
 <201403260826.28114.marex@denx.de>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <201403260826.28114.marex@denx.de>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org

On Wed, Mar 26, 2014 at 08:26:27AM +0100, Marek Vasut wrote:
> > > I think we disconnected here, sorry. Why can you not use (i2c_imx->dma !=
> > > NULL) instead of (i2c_imx->use_dma == true) please ?
> > 
> > But there are two judge conditions. But only the "i2c_imx->dma", but also
> > whether "i2c_imx_dma_request" success.
> > 
> > "i2c_imx->use_dma == true" be equivalent to "i2c_imx->dma != NULL &&
> > !i2c_imx_dma_request()"
> 
> +       /* Init DMA config if support*/
> +       i2c_imx->dma = devm_kzalloc(&pdev->dev, sizeof(struct imx_i2c_dma),
> +                                       GFP_KERNEL);
> +       if (!i2c_imx->dma) {
> +               dev_info(&pdev->dev,
> +                               "can't allocate dma struct faild use dma.\n");
> +               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;
> +       }
> 
> OK, looking at this one more time, why don't you wrap the allocation of i2c_imx-
> >dma into i2c_imx_dma_request() ? Even better, you can allocate *dma as a local 
> variable in i2c_imx_dma_request() and then assign it into i2c_imx->dma only at 
> the end of the i2c_imx_dma_request() function , at the point where you are sure 
> nothing failed. Then you can check i2c_imx->dma != NULL throughout the code to 
> check if the DMA is available, no ?
> 
> Shawn, Wolfram, am I talking nonsense or am I just not connecting ?

I'm with you, Marek.

Shawn

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/