linux-kernel - Re: [PATCH v3 2/5] mfd: syscon: add a DT property to set value width

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Message-ID: <564C94FF.10004@roeck-us.net>
Date:	Wed, 18 Nov 2015 07:10:55 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Damien Riegel <damien.riegel@...oirfairelinux.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-watchdog@...r.kernel.org, shawnguo@...nel.org,
	kernel@...gutronix.de, wim@...ana.be, robh+dt@...nel.org,
	sameo@...ux.intel.com, dinh.linux@...il.com,
	kernel@...oirfairelinux.com
Subject: Re: [PATCH v3 2/5] mfd: syscon: add a DT property to set value width

On 11/18/2015 12:21 AM, Lee Jones wrote:
[ ... ]
>>> Or, for more clarity:
>>>
>>>    of_property_read_u32(np, "bus-width", &bus_width);
>>>    if (bus_width)
>>>
>>> If you choose this version (which I think is my preferred method, don't
>>> forget to initialise 'bus_width' to zero.
>>>
>> Ignoring an error and depending on bus_width==0 to determine if the property
>> was provided seems odd, especially since it would "hide" if the bus-width
>> property is set to 0. In the original code, this would be detected as error.
>
> I'm not sure what you mean.  If bus_width==0, then a problem has
> occurred and we will not use the value.  If bus_width!=0 then we can
> assume that it's been set and (as the comment describes) the value
> will be checked for errors in regmap_init_mmio().
>

Your proposed code does not distinguish a missing property from "bus-width = <0>;".
It will silently ignore this case.

Guenter

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