linux-kernel - Re: [PATCH 1/3] i2c: add DMA support for freescale i2c driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Mon, 3 Mar 2014 12:14:12 +0100
From:	Marek Vasut <marex@...x.de>
To:	Yao Yuan <yao.yuan@...escale.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"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-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH 1/3] i2c: add DMA support for freescale i2c driver

On Monday, March 03, 2014 at 11:23:33 AM, Yao Yuan wrote:
> Hi, Marek
> 
> Marek Vasut wrote:
> > On Thursday, February 27, 2014 at 07:05:14 AM, Yuan Yao wrote:
> > 
> > [...]
> > 
> > > +static void i2c_imx_dma_free(struct imx_i2c_struct *i2c_imx) {
> > > +	struct imx_i2c_dma *dma = i2c_imx->dma;
> > > +	struct dma_chan *dma_chan;
> > > +
> > > +	dma_chan = dma->chan_tx;
> > > +	dma->chan_tx = NULL;
> > > +	dma->buf_tx = 0;
> > > +	dma->len_tx = 0;
> > > +	dma_release_channel(dma_chan);
> > > +
> > > +	dma_chan = dma->chan_rx;
> > > +	dma->chan_tx = NULL;
> > > +	dma->buf_rx = 0;
> > > +	dma->len_rx = 0;
> > > +	dma_release_channel(dma_chan);
> > 
> > You must make _DEAD_ _SURE_ this function is not ever called while the
> > DMA is still active. In your case, I have a feeling that's not handled.
> 
> Thanks for your attention.
> This few days I look up the code for the realization of
> dma_release_channel(). I found that it will disable the dma request first.
> So it's may safe. And drivers hadn't check whether dma is still active
> before dma_release_channel() as a usually usage. Because it will be
> disabled automatic.
> 
> The only problem is that, it will be forced to cancel the transfer which
> was not yet completed. Looking forward to hearing from you.

OK

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