[PATCH v2 0/2] nvmem: layouts: Add fixed-layout driver

[PATCH v2 0/2] nvmem: layouts: Add fixed-layout driver

[Mathieu Dubois-Briand]

Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
---
Changes in v2:
- Fixed dependency on core layout code with CONFIG_NVMEM_LAYOUTS
- Make fixed layout optional
- Link to v1: https://lore.kernel.org/r/20260505-mathieu-nvmem-fixed-layout-v1-1-7f6ecbce108d@bootlin.com

---
Mathieu Dubois-Briand (2):
      nvmem: layouts: Add fixed-layout driver
      nvmem: layouts: Make the fixed-layout driver optional

 MAINTAINERS                          |  5 ++++
 drivers/nvmem/core.c                 | 24 ++---------------
 drivers/nvmem/layouts.c              | 11 --------
 drivers/nvmem/layouts/Kconfig        |  8 ++++++
 drivers/nvmem/layouts/Makefile       |  1 +
 drivers/nvmem/layouts/fixed-layout.c | 52 ++++++++++++++++++++++++++++++++++++
 include/linux/nvmem-provider.h       |  7 +++++
 7 files changed, 75 insertions(+), 33 deletions(-)
---
base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32
change-id: 20260504-mathieu-nvmem-fixed-layout-24c6f8500bf6

Best regards,
-- 
Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>

[PATCH v2 1/2] nvmem: layouts: Add fixed-layout driver

[Mathieu Dubois-Briand]

Current implementation isn't working well when device tree nodes have a
phandle on a fixed-layout nvmem node. As the fixed layout is handled in
nvmem core, no driver is ever associated with the layout, and the device
consumer driver probe is deferred indefinitely.

Remove the specific handling of fixed-layout and add a layout driver.
This makes the fixed-layout similar to all other layouts, fixing the
whole issue.

Fixes: fc29fd821d9a ("nvmem: core: Rework layouts to become regular devices")
Cc: stable@vger.kernel.org
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
---
 MAINTAINERS                          |  5 ++++
 drivers/nvmem/core.c                 | 23 +---------------
 drivers/nvmem/layouts.c              | 11 --------
 drivers/nvmem/layouts/Makefile       |  1 +
 drivers/nvmem/layouts/fixed-layout.c | 52 ++++++++++++++++++++++++++++++++++++
 include/linux/nvmem-provider.h       |  7 +++++
 6 files changed, 66 insertions(+), 33 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS
index 882214b0e7db..c48c4e129736 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10018,6 +10018,11 @@ F:	drivers/base/firmware_loader/
 F:	rust/kernel/firmware.rs
 F:	include/linux/firmware.h
 
+FIXED-LAYOUT NVMEM LAYOUT DRIVER
+M:	Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
+S:	Maintained
+F:	drivers/nvmem/layouts/fixed-layout.c
+
 FLEXTIMER FTM-QUADDEC DRIVER
 M:	Patrick Havelange <patrick.havelange@essensium.com>
 L:	linux-iio@vger.kernel.org
diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 311cb2e5a5c0..0ec4924c4bda 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -786,7 +786,7 @@ static int nvmem_validate_keepouts(struct nvmem_device *nvmem)
 	return 0;
 }
 
-static int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct device_node *np)
+int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct device_node *np)
 {
 	struct device *dev = &nvmem->dev;
 	const __be32 *addr;
@@ -840,23 +840,6 @@ static int nvmem_add_cells_from_legacy_of(struct nvmem_device *nvmem)
 	return nvmem_add_cells_from_dt(nvmem, nvmem->dev.of_node);
 }
 
-static int nvmem_add_cells_from_fixed_layout(struct nvmem_device *nvmem)
-{
-	struct device_node *layout_np;
-	int err = 0;
-
-	layout_np = of_nvmem_layout_get_container(nvmem);
-	if (!layout_np)
-		return 0;
-
-	if (of_device_is_compatible(layout_np, "fixed-layout"))
-		err = nvmem_add_cells_from_dt(nvmem, layout_np);
-
-	of_node_put(layout_np);
-
-	return err;
-}
-
 int nvmem_layout_register(struct nvmem_layout *layout)
 {
 	int ret;
@@ -1005,10 +988,6 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config)
 			goto err_remove_cells;
 	}
 
-	rval = nvmem_add_cells_from_fixed_layout(nvmem);
-	if (rval)
-		goto err_remove_cells;
-
 	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);
 
 	rval = device_add(&nvmem->dev);
diff --git a/drivers/nvmem/layouts.c b/drivers/nvmem/layouts.c
index b90584e1b99e..07a34be9669c 100644
--- a/drivers/nvmem/layouts.c
+++ b/drivers/nvmem/layouts.c
@@ -125,11 +125,6 @@ static int nvmem_layout_create_device(struct nvmem_device *nvmem,
 	return 0;
 }
 
-static const struct of_device_id of_nvmem_layout_skip_table[] = {
-	{ .compatible = "fixed-layout", },
-	{}
-};
-
 static int nvmem_layout_bus_populate(struct nvmem_device *nvmem,
 				     struct device_node *layout_dn)
 {
@@ -142,12 +137,6 @@ static int nvmem_layout_bus_populate(struct nvmem_device *nvmem,
 		return 0;
 	}
 
-	/* Fixed layouts are parsed manually somewhere else for now */
-	if (of_match_node(of_nvmem_layout_skip_table, layout_dn)) {
-		pr_debug("%s() - skipping %pOF node\n", __func__, layout_dn);
-		return 0;
-	}
-
 	if (of_node_check_flag(layout_dn, OF_POPULATED_BUS)) {
 		pr_debug("%s() - skipping %pOF, already populated\n",
 			 __func__, layout_dn);
diff --git a/drivers/nvmem/layouts/Makefile b/drivers/nvmem/layouts/Makefile
index 4940c9db0665..dd6c6c70b1a9 100644
--- a/drivers/nvmem/layouts/Makefile
+++ b/drivers/nvmem/layouts/Makefile
@@ -3,6 +3,7 @@
 # Makefile for nvmem layouts.
 #
 
+obj-$(CONFIG_NVMEM_LAYOUTS) += fixed-layout.o
 obj-$(CONFIG_NVMEM_LAYOUT_SL28_VPD) += sl28vpd.o
 obj-$(CONFIG_NVMEM_LAYOUT_ONIE_TLV) += onie-tlv.o
 obj-$(CONFIG_NVMEM_LAYOUT_U_BOOT_ENV) += u-boot-env.o
diff --git a/drivers/nvmem/layouts/fixed-layout.c b/drivers/nvmem/layouts/fixed-layout.c
new file mode 100644
index 000000000000..bc7da9a904d4
--- /dev/null
+++ b/drivers/nvmem/layouts/fixed-layout.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2026 Bootlin
+ *
+ * Authors: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
+ */
+
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+
+static int fixed_layout_add_cells(struct nvmem_layout *layout)
+{
+	struct device_node *np;
+
+	np = of_nvmem_layout_get_container(layout->nvmem);
+	if (!np)
+		return -ENOENT;
+
+	return nvmem_add_cells_from_dt(layout->nvmem, np);
+}
+
+static int fixed_layout_probe(struct nvmem_layout *layout)
+{
+	layout->add_cells = fixed_layout_add_cells;
+
+	return nvmem_layout_register(layout);
+}
+
+static void fixed_layout_remove(struct nvmem_layout *layout)
+{
+	nvmem_layout_unregister(layout);
+}
+
+static const struct of_device_id fixed_layout_of_match_table[] = {
+	{ .compatible = "fixed-layout", },
+	{},
+};
+
+static struct nvmem_layout_driver fixed_layout_layout = {
+	.driver = {
+		.name = "fixed-layout",
+		.of_match_table = fixed_layout_of_match_table,
+	},
+	.probe = fixed_layout_probe,
+	.remove = fixed_layout_remove,
+};
+module_nvmem_layout_driver(fixed_layout_layout);
+
+MODULE_AUTHOR("Mathieu Dubois-Briand");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(of, fixed_layout_of_match_table);
+MODULE_DESCRIPTION("NVMEM fixed-layout driver");
diff --git a/include/linux/nvmem-provider.h b/include/linux/nvmem-provider.h
index f3b13da78aac..e7eaa9a89b8b 100644
--- a/include/linux/nvmem-provider.h
+++ b/include/linux/nvmem-provider.h
@@ -176,6 +176,7 @@ int nvmem_add_one_cell(struct nvmem_device *nvmem,
 
 int nvmem_layout_register(struct nvmem_layout *layout);
 void nvmem_layout_unregister(struct nvmem_layout *layout);
+int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct device_node *np);
 
 #define nvmem_layout_driver_register(drv) \
 	__nvmem_layout_driver_register(drv, THIS_MODULE)
@@ -214,6 +215,12 @@ static inline int nvmem_layout_register(struct nvmem_layout *layout)
 
 static inline void nvmem_layout_unregister(struct nvmem_layout *layout) {}
 
+static inline int nvmem_add_cells_from_dt(struct nvmem_device *nvmem,
+					  struct device_node *np)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif /* CONFIG_NVMEM */
 
 #if IS_ENABLED(CONFIG_NVMEM) && IS_ENABLED(CONFIG_OF)

-- 
2.47.3

[PATCH v2 2/2] nvmem: layouts: Make the fixed-layout driver optional

[Mathieu Dubois-Briand]

The fixed-layout support is now managed by a separate driver, so we can
make this support optional. This aligns with the approach taken for
other layout drivers.

Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
---
 drivers/nvmem/core.c           | 1 +
 drivers/nvmem/layouts/Kconfig  | 8 ++++++++
 drivers/nvmem/layouts/Makefile | 2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 0ec4924c4bda..594180d4b889 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -834,6 +834,7 @@ int nvmem_add_cells_from_dt(struct nvmem_device *nvmem, struct device_node *np)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(nvmem_add_cells_from_dt);
 
 static int nvmem_add_cells_from_legacy_of(struct nvmem_device *nvmem)
 {
diff --git a/drivers/nvmem/layouts/Kconfig b/drivers/nvmem/layouts/Kconfig
index 5e586dfebe47..f823d56210a3 100644
--- a/drivers/nvmem/layouts/Kconfig
+++ b/drivers/nvmem/layouts/Kconfig
@@ -8,6 +8,14 @@ if NVMEM_LAYOUTS
 
 menu "Layout Types"
 
+config NVMEM_LAYOUT_FIXED_LAYOUT
+	tristate "Fixed layout support"
+	help
+	  Say Y here to enable support for NVMEM fixed layout, which provides a
+	  way to describe memory cells with fixed offsets and sizes.
+
+	  If unsure, say N.
+
 config NVMEM_LAYOUT_SL28_VPD
 	tristate "Kontron sl28 VPD layout support"
 	select CRC8
diff --git a/drivers/nvmem/layouts/Makefile b/drivers/nvmem/layouts/Makefile
index dd6c6c70b1a9..9da790a9dde9 100644
--- a/drivers/nvmem/layouts/Makefile
+++ b/drivers/nvmem/layouts/Makefile
@@ -3,7 +3,7 @@
 # Makefile for nvmem layouts.
 #
 
-obj-$(CONFIG_NVMEM_LAYOUTS) += fixed-layout.o
+obj-$(CONFIG_NVMEM_LAYOUT_FIXED_LAYOUT) += fixed-layout.o
 obj-$(CONFIG_NVMEM_LAYOUT_SL28_VPD) += sl28vpd.o
 obj-$(CONFIG_NVMEM_LAYOUT_ONIE_TLV) += onie-tlv.o
 obj-$(CONFIG_NVMEM_LAYOUT_U_BOOT_ENV) += u-boot-env.o

-- 
2.47.3