linux-kernel - Re: [PATCH 6/6] dma/imx-sdma: check whether event_id0 < 32 when set event

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Message-ID: <20120111130910.GC27484@b20223-02.ap.freescale.net>
Date:	Wed, 11 Jan 2012 21:09:11 +0800
From:	Richard Zhao <richard.zhao@...escale.com>
To:	Shawn Guo <shawn.guo@...aro.org>
CC:	Eric Miao <eric.miao@...aro.org>, <patches@...aro.org>,
	<vinod.koul@...el.com>, <linux-kernel@...r.kernel.org>,
	<kernel@...gutronix.de>, <dan.j.williams@...el.com>,
	Richard Zhao <richard.zhao@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 6/6] dma/imx-sdma: check whether event_id0 < 32 when set
 event_mask

On Wed, Jan 11, 2012 at 09:16:17PM +0800, Shawn Guo wrote:
> On Wed, Jan 11, 2012 at 02:37:08PM +0800, Eric Miao wrote:
> > I think Richard has made the issue quite clear here, the original
> 
> Yes, he has made it clear, but only after I asked for more comments,
> not with the empty commit message.
> 
> > code does seem to have some problems even to me, who do not
> > understand the very details of the SDMA:
> > 
> > -                       sdmac->event_mask0 = 1 << sdmac->event_id0;
> > -                       sdmac->event_mask1 = 1 << (sdmac->event_id0 - 32);
> > 
> > 1. if sdmac->event_id0 >= 32, which will cause event_mask0 to be incorrect
> > 2. if sdmac->event_id < 32, sdmac->event_mask1 will be incorrect
> > 
> My testing tells this is not the case.  The event_mask0 will be 0 in
> case 1) and event_mask1 will be 0 in case 2), which is quite what we
> expect.  And I do not believe you will see any functionality bug with
> the existing code.
Please see my mail mentioned "we shoud not let it depends on gcc's
behavior."
> 
> See, that's why we need verbose commit message to make the patch and
> the problem it's trying to address very clear.
I never doubt it.

Thanks
Richard
> 
> Regards,
> Shawn
> 

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