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

Lee Jones
2015-11-23T08:20:19Z

On Sat, 21 Nov 2015, Arnd Bergmann wrote:

> On Tuesday 17 November 2015 09:26:49 Guenter Roeck wrote:
> > >
> > > This syntax is confusing, as we normally associate it with an error
> > > condition. Instead, I'd use:
> > >
> > > if (of_property_read_u32(np, "bus-width", &bus_width) == 0)
> >
> > Or maybe better
> >
> > if (!of_property_read_u32(np, "bus-width", &bus_width))
>
> I would also prefer the latter, but it doesn't matter much either way.
>
> > >
> > > 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.
>
> Right.
>
> Another option would be
>
> ret = of_property_read_u32(np, "bus-width", &bus_width);
> /* no bus width provided, default to 32-bit */
> if (ret)
> bus_width = 32;
>
> syscon_config.val_bits = bus_width;
> syscon_config.reg_stride = syscon_config.val_bits / 8;
>
> which has the same effect but seems a little clearer to me.

Works for me.

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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