[PATCH v11 net-next 1/9] mfd: ocelot: add helper to get regmap from a resource

[Colin Foster <colin.foster@in-advantage.com>]

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.

Signed-off-by: Colin Foster <colin.foster@in-advantage.com>
---
 MAINTAINERS                |  5 +++++
 include/linux/mfd/ocelot.h | 27 +++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)
 create mode 100644 include/linux/mfd/ocelot.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 36f0a205c54a..4d9ccec78f18 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14413,6 +14413,11 @@ F:	net/dsa/tag_ocelot.c
 F:	net/dsa/tag_ocelot_8021q.c
 F:	tools/testing/selftests/drivers/net/ocelot/*
 
+OCELOT EXTERNAL SWITCH CONTROL
+M:	Colin Foster <colin.foster@in-advantage.com>
+S:	Supported
+F:	include/linux/mfd/ocelot.h
+
 OCXL (Open Coherent Accelerator Processor Interface OpenCAPI) DRIVER
 M:	Frederic Barrat <fbarrat@linux.ibm.com>
 M:	Andrew Donnellan <ajd@linux.ibm.com>
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)
+{
+	struct resource *res;
+	u32 __iomem *regs;
+
+	regs = 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);
+}
-- 
2.25.1