[PATCH v4 4/7] nvmem: layouts: add Microchip/SST SFDP EUI layout driver
Manikandan Muralidharan
manikandan.m at microchip.com
Tue Jun 30 02:24:03 PDT 2026
Add an NVMEM layout that exposes the factory-programmed EUI-48 identifier
from the Microchip/SST vendor SFDP parameter table (e.g. SST26VF064BEUI)
as a "mac-address" cell, for use as a network MAC address. The vendor
table is located at runtime via the SFDP NVMEM device (no offset in DT),
and a read_post_process callback reverses the LSB-first bytes into
canonical MAC order. Binds to an "nvmem-layout" node with compatible
"microchip,sst26vf-sfdp-eui".
Signed-off-by: Manikandan Muralidharan <manikandan.m at microchip.com>
---
MAINTAINERS | 6 +
drivers/nvmem/layouts/Kconfig | 10 ++
drivers/nvmem/layouts/Makefile | 1 +
drivers/nvmem/layouts/sst26vf-sfdp-eui.c | 182 +++++++++++++++++++++++
4 files changed, 199 insertions(+)
create mode 100644 drivers/nvmem/layouts/sst26vf-sfdp-eui.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 15011f5752a9..dc3411b0c3b5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17812,6 +17812,12 @@ F: Documentation/devicetree/bindings/sound/atmel,at91-ssc.yaml
F: drivers/misc/atmel-ssc.c
F: include/linux/atmel-ssc.h
+MICROCHIP SST SFDP EUI NVMEM LAYOUT DRIVER
+M: Manikandan Muralidharan <manikandan.m at microchip.com>
+S: Maintained
+F: Documentation/devicetree/bindings/nvmem/layouts/microchip,sst26vf-sfdp-eui.yaml
+F: drivers/nvmem/layouts/sst26vf-sfdp-eui.c
+
Microchip Timer Counter Block (TCB) Capture Driver
M: Kamel Bouhara <kamel.bouhara at bootlin.com>
L: linux-arm-kernel at lists.infradead.org (moderated for non-subscribers)
diff --git a/drivers/nvmem/layouts/Kconfig b/drivers/nvmem/layouts/Kconfig
index 5e586dfebe47..855c7db530da 100644
--- a/drivers/nvmem/layouts/Kconfig
+++ b/drivers/nvmem/layouts/Kconfig
@@ -26,6 +26,16 @@ config NVMEM_LAYOUT_ONIE_TLV
If unsure, say N.
+config NVMEM_LAYOUT_SST26VF_SFDP_EUI
+ tristate "Microchip/SST SFDP EUI-48 layout support"
+ help
+ Say Y here if you want to expose the factory-programmed EUI-48
+ identifier stored in the Microchip/SST vendor-specific SFDP parameter
+ table (e.g. SST26VF064BEUI) as NVMEM cells, so that network drivers
+ can use them as a MAC address.
+
+ If unsure, say N.
+
config NVMEM_LAYOUT_U_BOOT_ENV
tristate "U-Boot environment variables layout"
select CRC32
diff --git a/drivers/nvmem/layouts/Makefile b/drivers/nvmem/layouts/Makefile
index 4940c9db0665..b99eac1f63f2 100644
--- a/drivers/nvmem/layouts/Makefile
+++ b/drivers/nvmem/layouts/Makefile
@@ -5,4 +5,5 @@
obj-$(CONFIG_NVMEM_LAYOUT_SL28_VPD) += sl28vpd.o
obj-$(CONFIG_NVMEM_LAYOUT_ONIE_TLV) += onie-tlv.o
+obj-$(CONFIG_NVMEM_LAYOUT_SST26VF_SFDP_EUI) += sst26vf-sfdp-eui.o
obj-$(CONFIG_NVMEM_LAYOUT_U_BOOT_ENV) += u-boot-env.o
diff --git a/drivers/nvmem/layouts/sst26vf-sfdp-eui.c b/drivers/nvmem/layouts/sst26vf-sfdp-eui.c
new file mode 100644
index 000000000000..641318d6f0af
--- /dev/null
+++ b/drivers/nvmem/layouts/sst26vf-sfdp-eui.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * NVMEM layout for the factory-programmed EUI-48 identifier stored in the
+ * Microchip/SST vendor-specific SFDP parameter table (e.g. SST26VF064BEUI).
+ *
+ * The whole SFDP is exposed as a read-only NVMEM device by the SPI NOR core.
+ * This layout locates the Microchip vendor parameter table at runtime and
+ * registers the EUI-48 address as an NVMEM cell, so that a network driver can
+ * consume it as a MAC address. No offset is hardcoded in the device tree.
+ *
+ * Copyright (C) 2026 Microchip Technology Inc. and its subsidiaries
+ *
+ * Author: Manikandan Muralidharan <manikandan.m at microchip.com>
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/minmax.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/unaligned.h>
+#include <uapi/linux/if_ether.h>
+
+/* SFDP header and parameter header, as laid out on the flash. */
+struct sfdp_header {
+ u8 signature[4];
+ u8 minor;
+ u8 major;
+ u8 nph;
+ u8 unused;
+};
+
+struct sfdp_parameter_header {
+ u8 id_lsb;
+ u8 minor;
+ u8 major;
+ u8 length;
+ u8 parameter_table_pointer[3];
+ u8 id_msb;
+};
+
+#define SFDP_SIGNATURE 0x50444653U
+
+#define SFDP_PARAM_HEADER_ID(h) (((h)->id_msb << 8) | (h)->id_lsb)
+#define SFDP_PARAM_HEADER_PTP(h) get_unaligned_le24((h)->parameter_table_pointer)
+
+/* Microchip (vendor) parameter table identifier: id_msb << 8 | id_lsb. */
+#define SFDP_MCHP_VENDOR_ID 0x01bf
+
+#define SFDP_MCHP_EUI48_MARKER_OFFSET 0x60
+#define SFDP_MCHP_EUI48_MARKER 0x30
+#define SFDP_MCHP_EUI48_OFFSET 0x61
+
+static int sfdp_eui_read_post_process(void *priv, const char *id, int index,
+ unsigned int offset, void *buf,
+ size_t bytes)
+{
+ u8 *data = buf;
+ int i;
+
+ /* SFDP stores the address least-significant octet first; reverse it. */
+ for (i = 0; i < bytes / 2; i++)
+ swap(data[i], data[bytes - 1 - i]);
+
+ if (bytes == ETH_ALEN && !is_valid_ether_addr(buf))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int sfdp_eui_find_vendor_table(struct nvmem_device *nvmem, u32 *ptp)
+{
+ struct sfdp_parameter_header ph;
+ struct sfdp_header hdr;
+ int nph, i, ret;
+
+ ret = nvmem_device_read(nvmem, 0, sizeof(hdr), &hdr);
+ if (ret < 0)
+ return ret;
+
+ if (get_unaligned_le32(hdr.signature) != SFDP_SIGNATURE)
+ return -EINVAL;
+
+ /* The number of parameter headers (NPH) field is zero-based. */
+ nph = hdr.nph;
+
+ for (i = 0; i <= nph; i++) {
+ ret = nvmem_device_read(nvmem, sizeof(hdr) + i * sizeof(ph),
+ sizeof(ph), &ph);
+ if (ret < 0)
+ return ret;
+
+ if (SFDP_PARAM_HEADER_ID(&ph) != SFDP_MCHP_VENDOR_ID)
+ continue;
+
+ *ptp = SFDP_PARAM_HEADER_PTP(&ph);
+ return 0;
+ }
+
+ return -ENOENT;
+}
+
+static int sfdp_eui_add_cells(struct nvmem_layout *layout)
+{
+ struct nvmem_device *nvmem = layout->nvmem;
+ struct device *dev = &layout->dev;
+ struct nvmem_cell_info info = { };
+ struct device_node *layout_np;
+ u32 base = 0;
+ u8 marker;
+ int ret;
+
+ ret = sfdp_eui_find_vendor_table(nvmem, &base);
+ if (ret == -ENOENT) {
+ dev_dbg(dev, "no Microchip SFDP vendor table found\n");
+ return 0;
+ }
+ if (ret)
+ return ret;
+
+ /* The EUI-48 is present only if its marker byte is programmed. */
+ ret = nvmem_device_read(nvmem, base + SFDP_MCHP_EUI48_MARKER_OFFSET,
+ 1, &marker);
+ if (ret < 0)
+ return ret;
+ if (marker != SFDP_MCHP_EUI48_MARKER) {
+ dev_dbg(dev, "EUI-48 not programmed (marker 0x%02x)\n", marker);
+ return 0;
+ }
+
+ layout_np = of_nvmem_layout_get_container(nvmem);
+ if (!layout_np)
+ return -ENOENT;
+
+ info.name = "mac-address";
+ info.offset = base + SFDP_MCHP_EUI48_OFFSET;
+ info.bytes = ETH_ALEN;
+ info.np = of_get_child_by_name(layout_np, "mac-address");
+ info.read_post_process = sfdp_eui_read_post_process;
+
+ ret = nvmem_add_one_cell(nvmem, &info);
+ if (ret)
+ of_node_put(info.np);
+ else
+ dev_dbg(dev, "exposed EUI-48 at SFDP offset 0x%x\n", info.offset);
+
+ of_node_put(layout_np);
+
+ return ret;
+}
+
+static int sfdp_eui_probe(struct nvmem_layout *layout)
+{
+ layout->add_cells = sfdp_eui_add_cells;
+
+ return nvmem_layout_register(layout);
+}
+
+static void sfdp_eui_remove(struct nvmem_layout *layout)
+{
+ nvmem_layout_unregister(layout);
+}
+
+static const struct of_device_id sfdp_eui_of_match_table[] = {
+ { .compatible = "microchip,sst26vf-sfdp-eui" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, sfdp_eui_of_match_table);
+
+static struct nvmem_layout_driver sfdp_eui_layout = {
+ .driver = {
+ .name = "microchip-sst26vf-sfdp-eui-layout",
+ .of_match_table = sfdp_eui_of_match_table,
+ },
+ .probe = sfdp_eui_probe,
+ .remove = sfdp_eui_remove,
+};
+module_nvmem_layout_driver(sfdp_eui_layout);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Manikandan Muralidharan <manikandan.m at microchip.com>");
+MODULE_DESCRIPTION("NVMEM layout for the EUI-48 in the Microchip/SST SFDP vendor table");
--
2.43.0
More information about the linux-arm-kernel
mailing list