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

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Date:	Wed, 18 Nov 2015 15:27:55 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Guenter Roeck <linux@...ck-us.net>
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 Wed, 18 Nov 2015, Guenter Roeck wrote:

> 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.

Okay, so what you're saying is, you'd prefer to throw and error
instead of using the default.  Fair point.  If this is an issue then
feel free to use either of the other two suggestions.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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