linux-kernel - Re: [PATCH v3.4-rc3] MTD: NAND: ams-delta: Fix request_mem

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Date:	Wed, 25 Apr 2012 18:13:38 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Janusz Krzysztofik <jkrzyszt@....icnet.pl>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Tony Lindgren <tony@...mide.com>,
	Artem Bityutskiy <Artem.Bityutskiy@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH v3.4-rc3] MTD: NAND: ams-delta: Fix request_mem_region()
 failure

On Tue, 2012-04-17 at 15:49 +0200, Janusz Krzysztofik wrote:
> A call to request_mem_region() has been introduced in the omap-gpio
> driver recently (commit 96751fcbe5438e95514b025e9cee7a6d38038f40,
> "gpio/omap: Use devm_ API and add request_mem_region"). This change
> prevented the Amstrad Delta NAND driver, which was doing the same in
> order to take control over OMAP MPU I/O lines that the NAND device hangs
> off, from loading successfully.
> 
> There is another driver, omap-keypad, which also manipulates OMAP MPUIO
> registers, but has never been calling request_mem_region() on startup,
> so it's not affected by the change in the gpio-omap and works correctly.
> 
> Drop request_mem_region() call and related bits from ams-delta NAND
> driver.
> 
> Created and tested against linux-3.4-rc3.
> 
> Signed-off-by: Janusz Krzysztofik <jkrzyszt@....icnet.pl>

How about race conditions? Where is the guarantee that these 2 drivers
won't affect each other when doing I/O at the same time to the same HW
resources?

-- 
Best Regards,
Artem Bityutskiy

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