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

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Date:	Thu, 29 Jan 2015 11:34:26 -0500
From:	Peter Hurley <peter@...leysoftware.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>,
	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 01/29/2015 11:05 AM, Russell King - ARM Linux wrote:
> 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.

Maybe the purpose would be better served by wrapping the idiom in a single
function.

Regards,
Peter Hurley
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