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From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     Colin Foster <colin.foster@in-advantage.com>
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Subject: Re: [PATCH v11 net-next 1/9] mfd: ocelot: add helper to get regmap
 from a resource
Thread-Topic: [PATCH v11 net-next 1/9] mfd: ocelot: add helper to get regmap
 from a resource
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Date:   Tue, 28 Jun 2022 16:08:10 +0000
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On Tue, Jun 28, 2022 at 01:17:01AM -0700, Colin Foster wrote:
> diff --git a/include/linux/mfd/ocelot.h b/include/linux/mfd/ocelot.h
> new file mode 100644
> index 000000000000..5c95e4ee38a6
> --- /dev/null
> +++ b/include/linux/mfd/ocelot.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 OR MIT */
> +/* Copyright 2022 Innovative Advantage Inc. */
> +
> +#include <linux/err.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>
> +
> +struct resource;
> +
> +static inline struct regmap *
> +ocelot_platform_init_regmap_from_resource(struct platform_device *pdev,
> +					  unsigned int index,
> +					  const struct regmap_config *config)

I think this function name is too long (especially if you're going to
also introduce ocelot_platform_init_regmap_from_resource_optional),
and I have the impression that the "platform_init_" part of the name
doesn't bring too much value. How about ocelot_regmap_from_resource()?

> +{
> +	struct resource *res;
> +	u32 __iomem *regs;
> +
> +	regs =3D devm_platform_get_and_ioremap_resource(pdev, index, &res);
> +
> +	if (!res)
> +		return ERR_PTR(-ENOENT);
> +	else if (IS_ERR(regs))
> +		return ERR_CAST(regs);
> +	else
> +		return devm_regmap_init_mmio(&pdev->dev, regs, config);
> +}
> --=20
> 2.25.1
>

To illustrate what I'm trying to say, these would be the shim
definitions:

static inline struct regmap *
ocelot_regmap_from_resource(struct platform_device *pdev,
			    unsigned int index,
			    const struct regmap_config *config)
{
	struct resource *res;
	void __iomem *regs;

	regs =3D devm_platform_get_and_ioremap_resource(pdev, index, &res);
	if (IS_ERR(regs))
		return regs;

	return devm_regmap_init_mmio(&pdev->dev, regs, config);
}

static inline struct regmap *
ocelot_regmap_from_resource_optional(struct platform_device *pdev,
				     unsigned int index,
				     const struct regmap_config *config)
{
	struct resource *res;
	void __iomem *regs;

	res =3D platform_get_resource(pdev, IORESOURCE_MEM, index);
	if (!res)
		return NULL;

	regs =3D devm_ioremap_resource(&pdev->dev, r);
	if (IS_ERR(regs))
		return regs;

	return devm_regmap_init_mmio(&pdev->dev, regs, config);
}

and these would be the full versions:

static struct regmap *
ocelot_regmap_from_mem_resource(struct device *dev, struct resource *res,
				const struct regmap_config *config)
{
	void __iomem *regs;

	regs =3D devm_ioremap_resource(dev, r);
	if (IS_ERR(regs))
		return regs;

	return devm_regmap_init_mmio(dev, regs, config);
}

static struct regmap *
ocelot_regmap_from_reg_resource(struct device *dev, struct resource *res,
				const struct regmap_config *config)
{
	/* Open question: how to differentiate SPI from I2C resources? */
	return ocelot_spi_init_regmap(dev->parent, dev, res);
}

struct regmap *
ocelot_regmap_from_resource_optional(struct platform_device *pdev,
				     unsigned int index,
				     const struct regmap_config *config)
{
	struct device *dev =3D &pdev->dev;
	struct resource *res;

	res =3D platform_get_resource(pdev, IORESOURCE_MEM, index);
	if (res)
		return ocelot_regmap_from_mem_resource(dev, res, config);

	/*
	 * Fall back to using IORESOURCE_REG, which is possible in an
	 * MFD configuration
	 */
	res =3D platform_get_resource(pdev, IORESOURCE_REG, index);
	if (res)
		return ocelot_regmap_from_reg_resource(dev, res, config);

	return NULL;
}

struct regmap *
ocelot_regmap_from_resource(struct platform_device *pdev,
			    unsigned int index,
			    const struct regmap_config *config)
{
	struct regmap *map;

	map =3D ocelot_regmap_from_resource_optional(pdev, index, config);
	return map ? : ERR_PTR(-ENOENT);
}

I hope I didn't get something wrong, this is all code written within the
email client, so it is obviously not compiled/tested....=