linux-kernel - Re: [PATCH v10 2/2] tty/serial: Add Spreadtrum sc9836-uart driver support

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Message-ID: <20150129160553.GC26493@n2100.arm.linux.org.uk>
Date:	Thu, 29 Jan 2015 16:05:53 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Peter Hurley <peter@...leysoftware.com>,
	Thierry Reding <thierry.reding@...il.com>
Cc:	Varka Bhadram <varkabhadram@...il.com>,
	Chunyan Zhang <chunyan.zhang@...eadtrum.com>,
	gregkh@...uxfoundation.org, mark.rutland@....com,
	gnomes@...rguk.ukuu.org.uk, heiko@...ech.de, andrew@...n.ch,
	jslaby@...e.cz, lanqing.liu@...eadtrum.com, pawel.moll@....com,
	zhang.lyra@...il.com, zhizhou.zhang@...eadtrum.com,
	geng.ren@...eadtrum.com, antonynpavlov@...il.com,
	linux-serial@...r.kernel.org, grant.likely@...aro.org,
	orsonzhai@...il.com, florian.vaussard@...l.ch,
	devicetree@...r.kernel.org, jason@...edaemon.net, arnd@...db.de,
	ijc+devicetree@...lion.org.uk, hytszk@...il.com,
	robh+dt@...nel.org, wei.qiao@...eadtrum.com,
	linux-arm-kernel@...ts.infradead.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org, galak@...eaurora.org,
	shawn.guo@...aro.org
Subject: Re: [PATCH v10 2/2] tty/serial: Add Spreadtrum sc9836-uart driver
 support

On Thu, Jan 29, 2015 at 10:49:34AM -0500, Peter Hurley wrote:
> Hi Varka,
> 
> On 01/29/2015 10:26 AM, Varka Bhadram wrote:
> > This check is not required. It will be done by devm_ioremap_resource()
> 
> I disagree. devm_ioremap_resource() interprets the NULL resource as
> a bad parameter and returns -EINVAL which is then forwarded as the
> return value from the probe.
> 
> -ENODEV is the correct return value from the probe if the expected
> resource is not available (either because it doesn't exist or was already
> claimed by another driver).

(Adding Thierry as the author of this function.)

I believe devm_ioremap_resource() was explicitly designed to remove such
error handling from drivers, and to give drivers a unified error response
to such things as missing resources.

See the comments for this function in lib/devres.c.

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