Re: [PATCH v12 net-next 1/9] mfd: ocelot: add helper to get regmap from a resource

Colin Foster
2022-07-01T20:35:06Z

On Fri, Jul 01, 2022 at 10:23:36PM +0200, Andy Shevchenko wrote:
> On Fri, Jul 1, 2022 at 9:26 PM Colin Foster
> <colin.foster@in-advantage.com> wrote:
> >
> > Several ocelot-related modules are designed for MMIO / regmaps. As such,
> > they often use a combination of devm_platform_get_and_ioremap_resource and
> > devm_regmap_init_mmio.
> >
> > Operating in an MFD might be different, in that it could be memory mapped,
> > or it could be SPI, I2C... In these cases a fallback to use IORESOURCE_REG
> > instead of IORESOURCE_MEM becomes necessary.
> >
> > When this happens, there's redundant logic that needs to be implemented in
> > every driver. In order to avoid this redundancy, utilize a single function
> > that, if the MFD scenario is enabled, will perform this fallback logic.
>
> ...
>
> > + res = platform_get_resource(pdev, IORESOURCE_MEM, index);
> > + if (res) {
> > + regs = devm_ioremap_resource(dev, res);
> > + if (IS_ERR(regs))
> > + return ERR_CAST(regs);
>
> Why can't it be devm_platform_get_and_ioremap_resource() here?

It can... but it invokes prints of "invalid resource" during
initialization.

Here it was implied that I should break the function call out:
https://patchwork.kernel.org/project/netdevbpf/patch/20220628081709.829811-2-colin.foster@in-advantage.com/#24917551

>
> regs = devm_platform_get_and_ioremap_resource();
> if (res) {
> if (IS_ERR(regs))
> return ERR_CAST();
> return ...
> }
>
> > + return devm_regmap_init_mmio(dev, regs, config);
> > + }
>
> ...
>
> > + return (map) ? map : ERR_PTR(-ENOENT);
>
> Too many parentheses.
>
> Also you may use short form of ternary operator:
>
> return map ?: ERR_PTR(-ENOENT);

Agreed, and I didn't know about that operator. When Vladimir suggested
it I thought it was a typo. I should've known better.

>
> --
> With Best Regards,
> Andy Shevchenko