[PATCH v4 0/8] Support for block device NVMEM providers

[PATCH v4 0/8] Support for block device NVMEM providers

[Loic Poulain]

On embedded devices, it is common for factory provisioning to store
device-specific information, such as Ethernet or WiFi MAC addresses,
in a dedicated area of an eMMC partition. This avoids the need for
and additional EEPROM/OTP and leverages the persistence of eMMC.

One example is the Arduino UNO-Q, where the WiFi MAC address and the
Bluetooth Device address are stored in the eMMC Boot1 partition.

Until now, accessing this information required a custom bootloader
to read the data and inject it into the Device Tree before handing
control over to the kernel. This approach is fragile and leads to
device-specific workarounds.

Rather than adding a new NVMEM provider specifically to the eMMC
subsystem, the new support operates at the block layer, allowing any
block device to behave like other non-volatile memories such as EEPROM
or OTP.

This series builds on earlier work by Daniel Golle that enables block
devices to act as NVMEM providers:
https://lore.kernel.org/all/6061aa4201030b9bb2f8d03ef32a564fdb786ed1.1709667858.git.daniel@makrotopia.org/

It also introduces an NVMEM layout description for the Arduino UNO-Q,
allowing device-specific data stored in the eMMC Boot1 partition to
be accessed in a standard way.

WiFi and Ethernet already support retrieving MAC addresses from NVMEM.
Bluetooth requires similar support, which is also addressed.

Note that this is currently limited to MMC-backed block devices, as
only the MMC core associates a firmware node with the block device
(add_disk_fwnode). This can be easily extended in the future to
support additional block drivers.

Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
Changes in v4:
- Fix squash issue (dts commit incorrectly squashed) (Konrad)
- Use devres for nvmem resources (Bartosz)
- use __free() destructor helper when possible (Bartosz)
- Fix value return checking for bdev_file_open_by_dev
- Link to v3: https://lore.kernel.org/r/20260608-block-as-nvmem-v3-0-82681f50aa35@oss.qualcomm.com

Changes in v3:
- Fixed missing 'fixed-partitions' compatible in partition (Rob)
- Fixed clashing nvmem cells, document calibration along mac (Sashiko)
- Remove workaround to handle dangling nvmem references after
  unregistering, this is a generic nvmem framework issue handled
  in Bartosz's series:
   https://lore.kernel.org/all/20260429-nvmem-unbind-v3-0-2a694f95395b@oss.qualcomm.com/
- Validate mac (is_valid_ether_addr) before copying to output buffer
- Link to v2: https://lore.kernel.org/r/20260507-block-as-nvmem-v2-0-bf17edd5134e@oss.qualcomm.com

Changes in v2:
- Fix example nvmem-layout cells to use compatible = "mac-base"
- Squash WiFi MAC and Bluetooth BD address consumer patches into the nvmem layout patch
- Fix possible use-after-free in blk-nvmem: bnv (nvmem priv) linked to nvmem lifetime
- Simplify nvmem-cell-names from items: - const: to plain const:
- Factor out common NVMEM EUI-48 retrieval logic
- Reorder changes
- Link to v1: https://lore.kernel.org/r/20260428-block-as-nvmem-v1-0-6ad23e75190a@oss.qualcomm.com

---
Daniel Golle (1):
      block: implement NVMEM provider

Loic Poulain (7):
      dt-bindings: mmc: Document support for nvmem-layout
      dt-bindings: net: wireless: qcom,ath10k: Document NVMEM cells
      dt-bindings: bluetooth: qcom: Add NVMEM BD address cell
      net: of_net: Add of_get_nvmem_eui48() helper for EUI-48 lookup
      Bluetooth: hci_sync: Add NVMEM-backed BD address retrieval
      Bluetooth: qca: Set NVMEM BD address quirks when address is invalid
      arm64: dts: qcom: arduino-imola: Describe NVMEM layout for WiFi/BT addresses

 .../devicetree/bindings/mmc/mmc-card.yaml          |  29 ++++++
 .../net/bluetooth/qcom,bluetooth-common.yaml       |   9 ++
 .../bindings/net/wireless/qcom,ath10k.yaml         |  16 +++
 arch/arm64/boot/dts/qcom/qrb2210-arduino-imola.dts |  39 +++++++
 block/Kconfig                                      |   9 ++
 block/Makefile                                     |   1 +
 block/blk-nvmem.c                                  | 114 +++++++++++++++++++++
 drivers/bluetooth/btqca.c                          |   5 +-
 include/linux/of_net.h                             |   7 ++
 include/net/bluetooth/hci.h                        |  18 ++++
 net/bluetooth/hci_sync.c                           |  39 ++++++-
 net/core/of_net.c                                  |  49 ++++++---
 12 files changed, 321 insertions(+), 14 deletions(-)
---
base-commit: 47c4835fc0fed583d01d90387b67633950eba2b2
change-id: 20260428-block-as-nvmem-4b308e8bda9a

Best regards,
-- 
Loic Poulain <loic.poulain@oss.qualcomm.com>

[PATCH v4 1/8] dt-bindings: mmc: Document support for nvmem-layout

[Loic Poulain]

Add support for an nvmem-layout subnode under an eMMC hardware
partition. This allows the partition to be exposed as an NVMEM
provider and its internal layout to be described. For example,
an eMMC boot partition can be used to store device-specific
information such as a WiFi MAC address.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 .../devicetree/bindings/mmc/mmc-card.yaml          | 29 ++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/mmc-card.yaml b/Documentation/devicetree/bindings/mmc/mmc-card.yaml
index a61d6c96df759102f9c1fbfd548b026a77921cae..ca907ad73095925b234b119948f94ae81e698c86 100644
--- a/Documentation/devicetree/bindings/mmc/mmc-card.yaml
+++ b/Documentation/devicetree/bindings/mmc/mmc-card.yaml
@@ -40,6 +40,9 @@ patternProperties:
         contains:
           const: fixed-partitions
 
+      nvmem-layout:
+        $ref: /schemas/nvmem/layouts/nvmem-layout.yaml
+
 required:
   - compatible
   - reg
@@ -86,6 +89,32 @@ examples:
                     read-only;
                 };
             };
+
+            partitions-boot2 {
+                compatible = "fixed-partitions";
+
+                #address-cells = <1>;
+                #size-cells = <1>;
+
+                nvmem-layout {
+                    compatible = "fixed-layout";
+
+                    #address-cells = <1>;
+                    #size-cells = <1>;
+
+                    mac-addr@4400 {
+                        compatible = "mac-base";
+                        reg = <0x4400 0x6>;
+                        #nvmem-cell-cells = <1>;
+                    };
+
+                    bd-addr@5400 {
+                        compatible = "mac-base";
+                        reg = <0x5400 0x6>;
+                        #nvmem-cell-cells = <1>;
+                    };
+                };
+            };
         };
     };
 

-- 
2.34.1

[PATCH v4 2/8] dt-bindings: net: wireless: qcom,ath10k: Document NVMEM cells

[Loic Poulain]

Document the NVMEM cells supported by the ath10k driver, the
mac-address, pre-calibration data, and calibration data.

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 .../devicetree/bindings/net/wireless/qcom,ath10k.yaml    | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml b/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
index c21d66c7cd558ab792524be9afec8b79272d1c87..7391df5e7071e626af4c64b9919d48c41ac09f1e 100644
--- a/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
+++ b/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
@@ -92,6 +92,22 @@ properties:
 
   ieee80211-freq-limit: true
 
+  nvmem-cells:
+    minItems: 1
+    maxItems: 3
+    description: |
+      References to nvmem cells for MAC address and/or calibration data.
+      Supported cell names are mac-address, calibration, and pre-calibration.
+
+  nvmem-cell-names:
+    minItems: 1
+    maxItems: 3
+    items:
+      enum:
+        - mac-address
+        - calibration
+        - pre-calibration
+
   qcom,calibration-data:
     $ref: /schemas/types.yaml#/definitions/uint8-array
     description:

-- 
2.34.1

[PATCH v4 3/8] dt-bindings: bluetooth: qcom: Add NVMEM BD address cell

[Loic Poulain]

Add support for an NVMEM cell provider for "local-bd-address",
allowing the Bluetooth stack to retrieve controller's BD address
from non-volatile storage such as an EEPROM or an eMMC partition.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 .../devicetree/bindings/net/bluetooth/qcom,bluetooth-common.yaml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/bluetooth/qcom,bluetooth-common.yaml b/Documentation/devicetree/bindings/net/bluetooth/qcom,bluetooth-common.yaml
index c8e9c55c1afb4c8e05ba2dae41ce2db4194b4a0f..7cb28f30c9af032082f23311f2fc89a32f266f17 100644
--- a/Documentation/devicetree/bindings/net/bluetooth/qcom,bluetooth-common.yaml
+++ b/Documentation/devicetree/bindings/net/bluetooth/qcom,bluetooth-common.yaml
@@ -22,4 +22,13 @@ properties:
     description:
       boot firmware is incorrectly passing the address in big-endian order
 
+  nvmem-cells:
+    maxItems: 1
+    description:
+      Nvmem data cell that contains a 6 byte BD address with the most
+      significant byte first (big-endian).
+
+  nvmem-cell-names:
+    const: local-bd-address
+
 additionalProperties: true

-- 
2.34.1

[PATCH v4 4/8] block: implement NVMEM provider

[Loic Poulain]

From: Daniel Golle <daniel@makrotopia.org>

On embedded devices using an eMMC it is common that one or more partitions
on the eMMC are used to store MAC addresses and Wi-Fi calibration EEPROM
data. Allow referencing the partition in device tree for the kernel and
Wi-Fi drivers accessing it via the NVMEM layer.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Co-developed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 block/Kconfig     |   9 +++++
 block/Makefile    |   1 +
 block/blk-nvmem.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 124 insertions(+)

diff --git a/block/Kconfig b/block/Kconfig
index 15027963472d7b40e27b9097a5993c457b5b3054..0b33747e16dc33473683706f75c92bdf8b648f7c 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -209,6 +209,15 @@ config BLK_INLINE_ENCRYPTION_FALLBACK
 	  by falling back to the kernel crypto API when inline
 	  encryption hardware is not present.
 
+config BLK_NVMEM
+	bool "Block device NVMEM provider"
+	depends on OF
+	depends on NVMEM
+	help
+	  Allow block devices (or partitions) to act as NVMEM providers,
+	  typically used with eMMC to store MAC addresses or Wi-Fi
+	  calibration data on embedded devices.
+
 source "block/partitions/Kconfig"
 
 config BLK_PM
diff --git a/block/Makefile b/block/Makefile
index 7dce2e44276c4274c11a0a61121c83d9c43d6e0c..d7ac389e71902bc091a8800ea266190a43b3e63d 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -36,3 +36,4 @@ obj-$(CONFIG_BLK_INLINE_ENCRYPTION)	+= blk-crypto.o blk-crypto-profile.o \
 					   blk-crypto-sysfs.o
 obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)	+= blk-crypto-fallback.o
 obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED)	+= holder.o
+obj-$(CONFIG_BLK_NVMEM)                += blk-nvmem.o
diff --git a/block/blk-nvmem.c b/block/blk-nvmem.c
new file mode 100644
index 0000000000000000000000000000000000000000..a6e62fa98675ee9bcb9c7035a611b5a573ab9091
--- /dev/null
+++ b/block/blk-nvmem.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * block device NVMEM provider
+ *
+ * Copyright (c) 2024 Daniel Golle <daniel@makrotopia.org>
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ *
+ * Useful on devices using a partition on an eMMC for MAC addresses or
+ * Wi-Fi calibration EEPROM data.
+ */
+
+#include <linux/file.h>
+#include <linux/nvmem-provider.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/of.h>
+#include <linux/pagemap.h>
+#include <linux/property.h>
+
+#include "blk.h"
+
+static int blk_nvmem_reg_read(void *priv, unsigned int from,
+			      void *val, size_t bytes)
+{
+	blk_mode_t mode = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES;
+	dev_t devt = (dev_t)(uintptr_t)priv;
+	size_t bytes_left = bytes;
+	loff_t pos = from;
+	int ret = 0;
+
+	struct file *bdev_file __free(fput) = bdev_file_open_by_dev(devt, mode, priv, NULL);
+	if (IS_ERR(bdev_file))
+		return PTR_ERR(bdev_file);
+
+	while (bytes_left) {
+		pgoff_t f_index = pos >> PAGE_SHIFT;
+		struct folio *folio;
+		size_t folio_off;
+		size_t to_read;
+
+		folio = read_mapping_folio(bdev_file->f_mapping, f_index, NULL);
+		if (IS_ERR(folio)) {
+			ret = PTR_ERR(folio);
+			break;
+		}
+
+		folio_off = offset_in_folio(folio, pos);
+		to_read = min(bytes_left, folio_size(folio) - folio_off);
+		memcpy_from_folio(val, folio, folio_off, to_read);
+		pos += to_read;
+		bytes_left -= to_read;
+		val += to_read;
+		folio_put(folio);
+	}
+
+	return ret;
+}
+
+static int blk_nvmem_register(struct device *dev)
+{
+	struct block_device *bdev = dev_to_bdev(dev);
+	struct nvmem_config config = {};
+
+	/* skip devices which do not have a device tree node */
+	if (!dev_of_node(dev))
+		return 0;
+
+	/* skip devices without an nvmem layout defined */
+	struct device_node *child __free(device_node) =
+		of_get_child_by_name(dev_of_node(dev), "nvmem-layout");
+	if (!child)
+		return 0;
+
+	/*
+	 * skip block device too large to be represented as NVMEM devices,
+	 * the NVMEM reg_read callback uses an unsigned int offset
+	 */
+	if (bdev_nr_bytes(bdev) > UINT_MAX) {
+		dev_warn(dev, "block device too large to be an NVMEM provider\n");
+		return -ENODEV;
+	}
+
+	config.id = NVMEM_DEVID_NONE;
+	config.dev = dev;
+	config.name = dev_name(dev);
+	config.owner = THIS_MODULE;
+	config.priv = (void *)(uintptr_t)dev->devt;
+	config.reg_read = blk_nvmem_reg_read;
+	config.size = bdev_nr_bytes(bdev);
+	config.word_size = 1;
+	config.stride = 1;
+	config.read_only = true;
+	config.root_only = true;
+	config.ignore_wp = true;
+	config.of_node = to_of_node(dev->fwnode);
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
+}
+
+static struct class_interface blk_nvmem_bus_interface __refdata = {
+	.class = &block_class,
+	.add_dev = &blk_nvmem_register,
+};
+
+static int __init blk_nvmem_init(void)
+{
+	int ret;
+
+	ret = class_interface_register(&blk_nvmem_bus_interface);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+device_initcall(blk_nvmem_init);

-- 
2.34.1

[PATCH v4 5/8] net: of_net: Add of_get_nvmem_eui48() helper for EUI-48 lookup

[Loic Poulain]

Factor out the common NVMEM EUI-48 retrieval logic from
of_get_mac_address_nvmem() into a new of_get_nvmem_eui48() helper that
accepts the NVMEM cell name as a parameter. This allows other subsystems
(e.g. Bluetooth) to reuse the same lookup-validate-copy pattern with a
different cell name, without duplicating code.

of_get_mac_address_nvmem() is updated to call of_get_nvmem_eui48() with
"mac-address", preserving its existing behavior.

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 include/linux/of_net.h |  7 +++++++
 net/core/of_net.c      | 49 +++++++++++++++++++++++++++++++++++++------------
 2 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/include/linux/of_net.h b/include/linux/of_net.h
index d88715a0b3a52f87af23d47791bea3baf5be5200..7854ba555d9a55f3d020a37fe00a27ae52e0e5dc 100644
--- a/include/linux/of_net.h
+++ b/include/linux/of_net.h
@@ -15,6 +15,7 @@ struct net_device;
 extern int of_get_phy_mode(struct device_node *np, phy_interface_t *interface);
 extern int of_get_mac_address(struct device_node *np, u8 *mac);
 extern int of_get_mac_address_nvmem(struct device_node *np, u8 *mac);
+int of_get_nvmem_eui48(struct device_node *np, const char *cell_name, u8 *addr);
 int of_get_ethdev_address(struct device_node *np, struct net_device *dev);
 extern struct net_device *of_find_net_device_by_node(struct device_node *np);
 #else
@@ -34,6 +35,12 @@ static inline int of_get_mac_address_nvmem(struct device_node *np, u8 *mac)
 	return -ENODEV;
 }
 
+static inline int of_get_nvmem_eui48(struct device_node *np,
+				      const char *cell_name, u8 *addr)
+{
+	return -ENODEV;
+}
+
 static inline int of_get_ethdev_address(struct device_node *np, struct net_device *dev)
 {
 	return -ENODEV;
diff --git a/net/core/of_net.c b/net/core/of_net.c
index 93ea425b9248a23f4f95a336e9cdbf0053248e32..75341c186123e949fbe21f1e51fce3ac74d4f56b 100644
--- a/net/core/of_net.c
+++ b/net/core/of_net.c
@@ -61,9 +61,7 @@ static int of_get_mac_addr(struct device_node *np, const char *name, u8 *addr)
 int of_get_mac_address_nvmem(struct device_node *np, u8 *addr)
 {
 	struct platform_device *pdev = of_find_device_by_node(np);
-	struct nvmem_cell *cell;
-	const void *mac;
-	size_t len;
+	u8 mac[ETH_ALEN];
 	int ret;
 
 	/* Try lookup by device first, there might be a nvmem_cell_lookup
@@ -75,27 +73,54 @@ int of_get_mac_address_nvmem(struct device_node *np, u8 *addr)
 		return ret;
 	}
 
-	cell = of_nvmem_cell_get(np, "mac-address");
+	ret = of_get_nvmem_eui48(np, "mac-address", mac);
+	if (ret)
+		return ret;
+
+	if (!is_valid_ether_addr(mac))
+		return -EINVAL;
+
+	ether_addr_copy(addr, mac);
+	return 0;
+}
+EXPORT_SYMBOL(of_get_mac_address_nvmem);
+
+/**
+ * of_get_nvmem_eui48 - Read a 6-byte EUI-48 address from a named NVMEM cell.
+ * @np:		Device node to look up the NVMEM cell from.
+ * @cell_name:	Name of the NVMEM cell (e.g. "mac-address", "local-bd-address").
+ * @addr:	Output buffer for the 6-byte address.
+ *
+ * Reads the named NVMEM cell and validates that it contains a non-zero 6-byte
+ * address. Returns 0 on success, negative errno on failure.
+ */
+int of_get_nvmem_eui48(struct device_node *np, const char *cell_name, u8 *addr)
+{
+	struct nvmem_cell *cell;
+	const void *eui48;
+	size_t len;
+
+	cell = of_nvmem_cell_get(np, cell_name);
 	if (IS_ERR(cell))
 		return PTR_ERR(cell);
 
-	mac = nvmem_cell_read(cell, &len);
+	eui48 = nvmem_cell_read(cell, &len);
 	nvmem_cell_put(cell);
 
-	if (IS_ERR(mac))
-		return PTR_ERR(mac);
+	if (IS_ERR(eui48))
+		return PTR_ERR(eui48);
 
-	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
-		kfree(mac);
+	if (len != ETH_ALEN || !memchr_inv(eui48, 0, ETH_ALEN)) {
+		kfree(eui48);
 		return -EINVAL;
 	}
 
-	memcpy(addr, mac, ETH_ALEN);
-	kfree(mac);
+	memcpy(addr, eui48, ETH_ALEN);
+	kfree(eui48);
 
 	return 0;
 }
-EXPORT_SYMBOL(of_get_mac_address_nvmem);
+EXPORT_SYMBOL_GPL(of_get_nvmem_eui48);
 
 /**
  * of_get_mac_address()

-- 
2.34.1

[PATCH v4 6/8] Bluetooth: hci_sync: Add NVMEM-backed BD address retrieval

[Loic Poulain]

Some devices store the Bluetooth BD address in non-volatile
memory, which can be accessed through the NVMEM framework.
Similar to Ethernet or WiFi MAC addresses, add support for
reading the BD address from a 'local-bd-address' NVMEM cell.

As with the device-tree provided BD address, add a quirk to
indicate whether a device or platform should attempt to read
the address from NVMEM when no valid in-chip address is present.
Also add a quirk to indicate if the address is stored in
big-endian byte order.

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 include/net/bluetooth/hci.h | 18 ++++++++++++++++++
 net/bluetooth/hci_sync.c    | 39 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 572b1c620c5d653a1fe10b26c1b0ba33e8f4968f..7686466d1109253b0d75edeb5f6a99fb98ce4cc6 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -164,6 +164,24 @@ enum {
 	 */
 	HCI_QUIRK_BDADDR_PROPERTY_BROKEN,
 
+	/* When this quirk is set, the public Bluetooth address
+	 * initially reported by HCI Read BD Address command
+	 * is considered invalid. The public BD Address can be
+	 * retrieved via a 'local-bd-address' NVMEM cell.
+	 *
+	 * This quirk can be set before hci_register_dev is called or
+	 * during the hdev->setup vendor callback.
+	 */
+	HCI_QUIRK_USE_BDADDR_NVMEM,
+
+	/* When this quirk is set, the Bluetooth Device Address provided by
+	 * the 'local-bd-address' NVMEM is stored in big-endian order.
+	 *
+	 * This quirk can be set before hci_register_dev is called or
+	 * during the hdev->setup vendor callback.
+	 */
+	HCI_QUIRK_BDADDR_NVMEM_BE,
+
 	/* When this quirk is set, the duplicate filtering during
 	 * scanning is based on Bluetooth devices addresses. To allow
 	 * RSSI based updates, restart scanning if needed.
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index fd3aacdea512a37c22b9a2be90c89ddca4b4d99f..589ccdfa26c1281d6eb979370523fff0d7920302 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/property.h>
+#include <linux/of_net.h>
 
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci_core.h>
@@ -3588,6 +3589,37 @@ int hci_powered_update_sync(struct hci_dev *hdev)
 	return 0;
 }
 
+/**
+ * hci_dev_get_bd_addr_from_nvmem - Get the Bluetooth Device Address
+ *				    (BD_ADDR) for a HCI device from
+ *				    an NVMEM cell.
+ * @hdev:	The HCI device
+ *
+ * Search for 'local-bd-address' NVMEM cell in the device firmware node.
+ *
+ * All-zero BD addresses are rejected (unprovisioned).
+ */
+static int hci_dev_get_bd_addr_from_nvmem(struct hci_dev *hdev)
+{
+	struct device_node *np = dev_of_node(hdev->dev.parent);
+	u8 ba[sizeof(bdaddr_t)];
+	int err;
+
+	if (!np)
+		return -ENODEV;
+
+	err = of_get_nvmem_eui48(np, "local-bd-address", ba);
+	if (err)
+		return err;
+
+	if (hci_test_quirk(hdev, HCI_QUIRK_BDADDR_NVMEM_BE))
+		baswap(&hdev->public_addr, (bdaddr_t *)ba);
+	else
+		bacpy(&hdev->public_addr, (bdaddr_t *)ba);
+
+	return 0;
+}
+
 /**
  * hci_dev_get_bd_addr_from_property - Get the Bluetooth Device Address
  *				       (BD_ADDR) for a HCI device from
@@ -5042,12 +5074,17 @@ static int hci_dev_setup_sync(struct hci_dev *hdev)
 	 * its setup callback.
 	 */
 	invalid_bdaddr = hci_test_quirk(hdev, HCI_QUIRK_INVALID_BDADDR) ||
-			 hci_test_quirk(hdev, HCI_QUIRK_USE_BDADDR_PROPERTY);
+			 hci_test_quirk(hdev, HCI_QUIRK_USE_BDADDR_PROPERTY) ||
+			 hci_test_quirk(hdev, HCI_QUIRK_USE_BDADDR_NVMEM);
 	if (!ret) {
 		if (hci_test_quirk(hdev, HCI_QUIRK_USE_BDADDR_PROPERTY) &&
 		    !bacmp(&hdev->public_addr, BDADDR_ANY))
 			hci_dev_get_bd_addr_from_property(hdev);
 
+		if (hci_test_quirk(hdev, HCI_QUIRK_USE_BDADDR_NVMEM) &&
+		    !bacmp(&hdev->public_addr, BDADDR_ANY))
+			hci_dev_get_bd_addr_from_nvmem(hdev);
+
 		if (invalid_bdaddr && bacmp(&hdev->public_addr, BDADDR_ANY) &&
 		    hdev->set_bdaddr) {
 			ret = hdev->set_bdaddr(hdev, &hdev->public_addr);

-- 
2.34.1

[PATCH v4 7/8] Bluetooth: qca: Set NVMEM BD address quirks when address is invalid

[Loic Poulain]

When the controller BD address is invalid (zero or default),
set the NVMEM quirks to allow retrieving the address from a
'local-bd-address' NVMEM cell. The BD address is often stored
alongside the WiFi MAC address in big-endian format, so also
set the big-endian quirk.

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 drivers/bluetooth/btqca.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btqca.c b/drivers/bluetooth/btqca.c
index dda76365726f0bfe0e80e05fe04859fa4f0592e1..df33eacfd29fa680f393f90215150743e6001d5b 100644
--- a/drivers/bluetooth/btqca.c
+++ b/drivers/bluetooth/btqca.c
@@ -721,8 +721,11 @@ static int qca_check_bdaddr(struct hci_dev *hdev, const struct qca_fw_config *co
 	}
 
 	bda = (struct hci_rp_read_bd_addr *)skb->data;
-	if (!bacmp(&bda->bdaddr, &config->bdaddr))
+	if (!bacmp(&bda->bdaddr, &config->bdaddr)) {
 		hci_set_quirk(hdev, HCI_QUIRK_USE_BDADDR_PROPERTY);
+		hci_set_quirk(hdev, HCI_QUIRK_USE_BDADDR_NVMEM);
+		hci_set_quirk(hdev, HCI_QUIRK_BDADDR_NVMEM_BE);
+	}
 
 	kfree_skb(skb);
 

-- 
2.34.1

[PATCH v4 8/8] arm64: dts: qcom: arduino-imola: Describe NVMEM layout for WiFi/BT addresses

[Loic Poulain]

On Arduino Uno-Q, the eMMC boot1 partition is factory provisioned
with device-specific information such as the WiFi MAC address
and the Bluetooth BD address. This partition can serve as an
alternative to additional non-volatile memory, such as a
dedicated EEPROM.

The eMMC boot partitions are typically good candidates, as they
are relatively small, read-only by default (and can be enforced
as hardware read-only), and are not affected by board reflashing
procedures, which generally target the eMMC user or GP partitions.

Describe the corresponding nvmem-layout for the WiFi and Bluetooth
addresses, and point the WiFi and Bluetooth nodes to the appropriate
NVMEM cells to retrieve them.

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
---
 arch/arm64/boot/dts/qcom/qrb2210-arduino-imola.dts | 39 ++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/qrb2210-arduino-imola.dts b/arch/arm64/boot/dts/qcom/qrb2210-arduino-imola.dts
index bf088fa9807f040f0c8f405f9111b01790b09377..128c7a7e76b5b089044745f5d6407d6391055fc2 100644
--- a/arch/arm64/boot/dts/qcom/qrb2210-arduino-imola.dts
+++ b/arch/arm64/boot/dts/qcom/qrb2210-arduino-imola.dts
@@ -409,7 +409,40 @@ &sdhc_1 {
 	no-sdio;
 	no-sd;
 
+	#address-cells = <1>;
+	#size-cells = <0>;
+
 	status = "okay";
+
+	card@0 {
+		compatible = "mmc-card";
+		reg = <0>;
+
+		partitions-boot1 {
+			compatible = "fixed-partitions";
+
+			#address-cells = <1>;
+			#size-cells = <1>;
+
+			nvmem-layout {
+				compatible = "fixed-layout";
+				#address-cells = <1>;
+				#size-cells = <1>;
+
+				wifi_mac_addr: mac-addr@4400 {
+					compatible = "mac-base";
+					reg = <0x4400 0x6>;
+					#nvmem-cell-cells = <1>;
+				};
+
+				bd_addr: bd-addr@5400 {
+					compatible = "mac-base";
+					reg = <0x5400 0x6>;
+					#nvmem-cell-cells = <1>;
+				};
+			};
+		};
+	};
 };
 
 &spi5 {
@@ -512,6 +545,9 @@ bluetooth {
 		vddch0-supply = <&pm4125_l22>;
 		enable-gpios = <&tlmm 87 GPIO_ACTIVE_HIGH>;
 		max-speed = <3000000>;
+
+		nvmem-cells = <&bd_addr 0>;
+		nvmem-cell-names = "local-bd-address";
 	};
 };
 
@@ -557,6 +593,9 @@ &wifi {
 	qcom,ath10k-calibration-variant = "ArduinoImola";
 	firmware-name = "qcm2290";
 
+	nvmem-cells = <&wifi_mac_addr 0>;
+	nvmem-cell-names = "mac-address";
+
 	status = "okay";
 };
 

-- 
2.34.1

Re: [PATCH v4 4/8] block: implement NVMEM provider

[Bartosz Golaszewski]

On Tue, 9 Jun 2026 09:52:29 +0200, Loic Poulain
<loic.poulain@oss.qualcomm.com> said:
> From: Daniel Golle <daniel@makrotopia.org>
>
> On embedded devices using an eMMC it is common that one or more partitions
> on the eMMC are used to store MAC addresses and Wi-Fi calibration EEPROM
> data. Allow referencing the partition in device tree for the kernel and
> Wi-Fi drivers accessing it via the NVMEM layer.
>
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> Co-developed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
>  block/Kconfig     |   9 +++++
>  block/Makefile    |   1 +
>  block/blk-nvmem.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 124 insertions(+)
>
> diff --git a/block/Kconfig b/block/Kconfig
> index 15027963472d7b40e27b9097a5993c457b5b3054..0b33747e16dc33473683706f75c92bdf8b648f7c 100644
> --- a/block/Kconfig
> +++ b/block/Kconfig
> @@ -209,6 +209,15 @@ config BLK_INLINE_ENCRYPTION_FALLBACK
>  	  by falling back to the kernel crypto API when inline
>  	  encryption hardware is not present.
>
> +config BLK_NVMEM
> +	bool "Block device NVMEM provider"
> +	depends on OF
> +	depends on NVMEM
> +	help
> +	  Allow block devices (or partitions) to act as NVMEM providers,
> +	  typically used with eMMC to store MAC addresses or Wi-Fi
> +	  calibration data on embedded devices.
> +
>  source "block/partitions/Kconfig"
>
>  config BLK_PM
> diff --git a/block/Makefile b/block/Makefile
> index 7dce2e44276c4274c11a0a61121c83d9c43d6e0c..d7ac389e71902bc091a8800ea266190a43b3e63d 100644
> --- a/block/Makefile
> +++ b/block/Makefile
> @@ -36,3 +36,4 @@ obj-$(CONFIG_BLK_INLINE_ENCRYPTION)	+= blk-crypto.o blk-crypto-profile.o \
>  					   blk-crypto-sysfs.o
>  obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK)	+= blk-crypto-fallback.o
>  obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED)	+= holder.o
> +obj-$(CONFIG_BLK_NVMEM)                += blk-nvmem.o
> diff --git a/block/blk-nvmem.c b/block/blk-nvmem.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..a6e62fa98675ee9bcb9c7035a611b5a573ab9091
> --- /dev/null
> +++ b/block/blk-nvmem.c
> @@ -0,0 +1,114 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * block device NVMEM provider
> + *
> + * Copyright (c) 2024 Daniel Golle <daniel@makrotopia.org>
> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> + *
> + * Useful on devices using a partition on an eMMC for MAC addresses or
> + * Wi-Fi calibration EEPROM data.
> + */
> +
> +#include <linux/file.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/nvmem-consumer.h>
> +#include <linux/of.h>
> +#include <linux/pagemap.h>
> +#include <linux/property.h>
> +
> +#include "blk.h"
> +
> +static int blk_nvmem_reg_read(void *priv, unsigned int from,
> +			      void *val, size_t bytes)
> +{
> +	blk_mode_t mode = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES;
> +	dev_t devt = (dev_t)(uintptr_t)priv;
> +	size_t bytes_left = bytes;
> +	loff_t pos = from;
> +	int ret = 0;
> +
> +	struct file *bdev_file __free(fput) = bdev_file_open_by_dev(devt, mode, priv, NULL);
> +	if (IS_ERR(bdev_file))
> +		return PTR_ERR(bdev_file);
> +
> +	while (bytes_left) {
> +		pgoff_t f_index = pos >> PAGE_SHIFT;
> +		struct folio *folio;
> +		size_t folio_off;
> +		size_t to_read;
> +
> +		folio = read_mapping_folio(bdev_file->f_mapping, f_index, NULL);
> +		if (IS_ERR(folio)) {
> +			ret = PTR_ERR(folio);
> +			break;
> +		}
> +
> +		folio_off = offset_in_folio(folio, pos);
> +		to_read = min(bytes_left, folio_size(folio) - folio_off);
> +		memcpy_from_folio(val, folio, folio_off, to_read);
> +		pos += to_read;
> +		bytes_left -= to_read;
> +		val += to_read;
> +		folio_put(folio);
> +	}
> +
> +	return ret;
> +}
> +
> +static int blk_nvmem_register(struct device *dev)
> +{
> +	struct block_device *bdev = dev_to_bdev(dev);
> +	struct nvmem_config config = {};
> +
> +	/* skip devices which do not have a device tree node */
> +	if (!dev_of_node(dev))
> +		return 0;
> +
> +	/* skip devices without an nvmem layout defined */
> +	struct device_node *child __free(device_node) =
> +		of_get_child_by_name(dev_of_node(dev), "nvmem-layout");
> +	if (!child)
> +		return 0;
> +
> +	/*
> +	 * skip block device too large to be represented as NVMEM devices,
> +	 * the NVMEM reg_read callback uses an unsigned int offset
> +	 */
> +	if (bdev_nr_bytes(bdev) > UINT_MAX) {
> +		dev_warn(dev, "block device too large to be an NVMEM provider\n");
> +		return -ENODEV;

Wait, I must have suggested -ENODEV here on too little coffee. This callback
is called from device_add(), not when the device is bound so it's not the same
thing as returning -ENODEV from probe().

On the other hand, we don't want to not provide the block device just because
someone added a DT property on one that's too big. I'd say: warn, but return 0.
Does it make sense?

> +	}
> +
> +	config.id = NVMEM_DEVID_NONE;
> +	config.dev = dev;
> +	config.name = dev_name(dev);
> +	config.owner = THIS_MODULE;
> +	config.priv = (void *)(uintptr_t)dev->devt;
> +	config.reg_read = blk_nvmem_reg_read;
> +	config.size = bdev_nr_bytes(bdev);
> +	config.word_size = 1;
> +	config.stride = 1;
> +	config.read_only = true;
> +	config.root_only = true;
> +	config.ignore_wp = true;
> +	config.of_node = to_of_node(dev->fwnode);
> +
> +	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));

And that was a wrong suggestion on my part too because I was under the
impression that we're in the probe() path, not device_add(). You can't use
devres here as the device at this point is not yet bound and may never be.

Which leads me to the second point: this is not the moment to add the nvmem
provider. This should happen at or after probe(). Once nvmem_register()
returns, you have a visible nvmem resource but nothing backing it in the block
layer.

Either do this in block core when registering a new device or schedule
a notifier here for the BUS_NOTIFY_BOUND_DRIVER event and do it in the notifier
callback.

Sorry, I should have paid more attention, I forgot how the class interface
works.

> +}
> +
> +static struct class_interface blk_nvmem_bus_interface __refdata = {
> +	.class = &block_class,
> +	.add_dev = &blk_nvmem_register,
> +};
> +
> +static int __init blk_nvmem_init(void)
> +{
> +	int ret;
> +
> +	ret = class_interface_register(&blk_nvmem_bus_interface);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +device_initcall(blk_nvmem_init);
>
> --
> 2.34.1
>
>

Bart

Re: [PATCH v4 4/8] block: implement NVMEM provider

[Loic Poulain]

Hi bartosz,

On Tue, Jun 9, 2026 at 10:52 AM Bartosz Golaszewski <brgl@kernel.org> wrote:
>
> On Tue, 9 Jun 2026 09:52:29 +0200, Loic Poulain
> <loic.poulain@oss.qualcomm.com> said:
> > From: Daniel Golle <daniel@makrotopia.org>
> >
> > On embedded devices using an eMMC it is common that one or more partitions
> > on the eMMC are used to store MAC addresses and Wi-Fi calibration EEPROM
> > data. Allow referencing the partition in device tree for the kernel and
> > Wi-Fi drivers accessing it via the NVMEM layer.
> >
> > Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> > Co-developed-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> > Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> > ---
> >  block/Kconfig     |   9 +++++
> >  block/Makefile    |   1 +
> >  block/blk-nvmem.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 124 insertions(+)
> >
> > diff --git a/block/Kconfig b/block/Kconfig
> > index 15027963472d7b40e27b9097a5993c457b5b3054..0b33747e16dc33473683706f75c92bdf8b648f7c 100644
> > --- a/block/Kconfig
> > +++ b/block/Kconfig
> > @@ -209,6 +209,15 @@ config BLK_INLINE_ENCRYPTION_FALLBACK
> >         by falling back to the kernel crypto API when inline
> >         encryption hardware is not present.
> >
> > +config BLK_NVMEM
> > +     bool "Block device NVMEM provider"
> > +     depends on OF
> > +     depends on NVMEM
> > +     help
> > +       Allow block devices (or partitions) to act as NVMEM providers,
> > +       typically used with eMMC to store MAC addresses or Wi-Fi
> > +       calibration data on embedded devices.
> > +
> >  source "block/partitions/Kconfig"
> >
> >  config BLK_PM
> > diff --git a/block/Makefile b/block/Makefile
> > index 7dce2e44276c4274c11a0a61121c83d9c43d6e0c..d7ac389e71902bc091a8800ea266190a43b3e63d 100644
> > --- a/block/Makefile
> > +++ b/block/Makefile
> > @@ -36,3 +36,4 @@ obj-$(CONFIG_BLK_INLINE_ENCRYPTION) += blk-crypto.o blk-crypto-profile.o \
> >                                          blk-crypto-sysfs.o
> >  obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) += blk-crypto-fallback.o
> >  obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED)        += holder.o
> > +obj-$(CONFIG_BLK_NVMEM)                += blk-nvmem.o
> > diff --git a/block/blk-nvmem.c b/block/blk-nvmem.c
> > new file mode 100644
> > index 0000000000000000000000000000000000000000..a6e62fa98675ee9bcb9c7035a611b5a573ab9091
> > --- /dev/null
> > +++ b/block/blk-nvmem.c
> > @@ -0,0 +1,114 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * block device NVMEM provider
> > + *
> > + * Copyright (c) 2024 Daniel Golle <daniel@makrotopia.org>
> > + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
> > + *
> > + * Useful on devices using a partition on an eMMC for MAC addresses or
> > + * Wi-Fi calibration EEPROM data.
> > + */
> > +
> > +#include <linux/file.h>
> > +#include <linux/nvmem-provider.h>
> > +#include <linux/nvmem-consumer.h>
> > +#include <linux/of.h>
> > +#include <linux/pagemap.h>
> > +#include <linux/property.h>
> > +
> > +#include "blk.h"
> > +
> > +static int blk_nvmem_reg_read(void *priv, unsigned int from,
> > +                           void *val, size_t bytes)
> > +{
> > +     blk_mode_t mode = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES;
> > +     dev_t devt = (dev_t)(uintptr_t)priv;
> > +     size_t bytes_left = bytes;
> > +     loff_t pos = from;
> > +     int ret = 0;
> > +
> > +     struct file *bdev_file __free(fput) = bdev_file_open_by_dev(devt, mode, priv, NULL);
> > +     if (IS_ERR(bdev_file))
> > +             return PTR_ERR(bdev_file);
> > +
> > +     while (bytes_left) {
> > +             pgoff_t f_index = pos >> PAGE_SHIFT;
> > +             struct folio *folio;
> > +             size_t folio_off;
> > +             size_t to_read;
> > +
> > +             folio = read_mapping_folio(bdev_file->f_mapping, f_index, NULL);
> > +             if (IS_ERR(folio)) {
> > +                     ret = PTR_ERR(folio);
> > +                     break;
> > +             }
> > +
> > +             folio_off = offset_in_folio(folio, pos);
> > +             to_read = min(bytes_left, folio_size(folio) - folio_off);
> > +             memcpy_from_folio(val, folio, folio_off, to_read);
> > +             pos += to_read;
> > +             bytes_left -= to_read;
> > +             val += to_read;
> > +             folio_put(folio);
> > +     }
> > +
> > +     return ret;
> > +}
> > +
> > +static int blk_nvmem_register(struct device *dev)
> > +{
> > +     struct block_device *bdev = dev_to_bdev(dev);
> > +     struct nvmem_config config = {};
> > +
> > +     /* skip devices which do not have a device tree node */
> > +     if (!dev_of_node(dev))
> > +             return 0;
> > +
> > +     /* skip devices without an nvmem layout defined */
> > +     struct device_node *child __free(device_node) =
> > +             of_get_child_by_name(dev_of_node(dev), "nvmem-layout");
> > +     if (!child)
> > +             return 0;
> > +
> > +     /*
> > +      * skip block device too large to be represented as NVMEM devices,
> > +      * the NVMEM reg_read callback uses an unsigned int offset
> > +      */
> > +     if (bdev_nr_bytes(bdev) > UINT_MAX) {
> > +             dev_warn(dev, "block device too large to be an NVMEM provider\n");
> > +             return -ENODEV;
>
> Wait, I must have suggested -ENODEV here on too little coffee. This callback
> is called from device_add(), not when the device is bound so it's not the same
> thing as returning -ENODEV from probe().
>
> On the other hand, we don't want to not provide the block device just because
> someone added a DT property on one that's too big. I'd say: warn, but return 0.
> Does it make sense?

It’s still technically an error in the sense that we cannot provide
the required nvmem feature. However, it only becomes a real issue if a
consumer actually attempts to use it.
Also, the block device should still be added, since the return code
from add_dev is not checked. In any case, I’m fine with either
approach, as long as we emit a warning message.

>
> > +     }
> > +
> > +     config.id = NVMEM_DEVID_NONE;
> > +     config.dev = dev;
> > +     config.name = dev_name(dev);
> > +     config.owner = THIS_MODULE;
> > +     config.priv = (void *)(uintptr_t)dev->devt;
> > +     config.reg_read = blk_nvmem_reg_read;
> > +     config.size = bdev_nr_bytes(bdev);
> > +     config.word_size = 1;
> > +     config.stride = 1;
> > +     config.read_only = true;
> > +     config.root_only = true;
> > +     config.ignore_wp = true;
> > +     config.of_node = to_of_node(dev->fwnode);
> > +
> > +     return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
>
> And that was a wrong suggestion on my part too because I was under the
> impression that we're in the probe() path, not device_add(). You can't use
> devres here as the device at this point is not yet bound and may never be.

So I understand The bd_device is purely a class device with no bus, no driver.
For driverless devices, devres_release_all() is called explicitly
within device_del() .

>
> Which leads me to the second point: this is not the moment to add the nvmem
> provider. This should happen at or after probe(). Once nvmem_register()
> returns, you have a visible nvmem resource but nothing backing it in the block
> layer.

There is a short window during which a read attempt will 'properly'
fail, but this does seem somewhat fragile indeed.

> Either do this in block core when registering a new device or schedule
> a notifier here for the BUS_NOTIFY_BOUND_DRIVER event and do it in the notifier
> callback.

So in the end, it seems that the simpler and more robust approach is
probably to move away from the class_interface driver and instead
register/unregister the nvmem directly in add_disk/del_gendisk.
If that's ok I will move to this approach in the next version.

Regards,
Loic

Re: [PATCH v4 4/8] block: implement NVMEM provider

[Bartosz Golaszewski]

On Tue, 9 Jun 2026 12:13:08 +0200, Loic Poulain
<loic.poulain@oss.qualcomm.com> said:
> Hi bartosz,
>

...

>>
>> On the other hand, we don't want to not provide the block device just because
>> someone added a DT property on one that's too big. I'd say: warn, but return 0.
>> Does it make sense?
>
> It’s still technically an error in the sense that we cannot provide
> the required nvmem feature. However, it only becomes a real issue if a
> consumer actually attempts to use it.
> Also, the block device should still be added, since the return code
> from add_dev is not checked. In any case, I’m fine with either
> approach, as long as we emit a warning message.
>

We don't check the return value now (why?) but if we ever do, the safer option
is to return 0 IMO.

>>
>> > +     }
>> > +
>> > +     config.id = NVMEM_DEVID_NONE;
>> > +     config.dev = dev;
>> > +     config.name = dev_name(dev);
>> > +     config.owner = THIS_MODULE;
>> > +     config.priv = (void *)(uintptr_t)dev->devt;
>> > +     config.reg_read = blk_nvmem_reg_read;
>> > +     config.size = bdev_nr_bytes(bdev);
>> > +     config.word_size = 1;
>> > +     config.stride = 1;
>> > +     config.read_only = true;
>> > +     config.root_only = true;
>> > +     config.ignore_wp = true;
>> > +     config.of_node = to_of_node(dev->fwnode);
>> > +
>> > +     return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
>>
>> And that was a wrong suggestion on my part too because I was under the
>> impression that we're in the probe() path, not device_add(). You can't use
>> devres here as the device at this point is not yet bound and may never be.
>
> So I understand The bd_device is purely a class device with no bus, no driver.
> For driverless devices, devres_release_all() is called explicitly
> within device_del() .
>

Right.

>>
>> Which leads me to the second point: this is not the moment to add the nvmem
>> provider. This should happen at or after probe(). Once nvmem_register()
>> returns, you have a visible nvmem resource but nothing backing it in the block
>> layer.
>
> There is a short window during which a read attempt will 'properly'
> fail, but this does seem somewhat fragile indeed.
>
>> Either do this in block core when registering a new device or schedule
>> a notifier here for the BUS_NOTIFY_BOUND_DRIVER event and do it in the notifier
>> callback.
>
> So in the end, it seems that the simpler and more robust approach is
> probably to move away from the class_interface driver and instead
> register/unregister the nvmem directly in add_disk/del_gendisk.
> If that's ok I will move to this approach in the next version.
>

Yes, I think it's the right approach.

Bart

Re: [PATCH v4 2/8] dt-bindings: net: wireless: qcom,ath10k: Document NVMEM cells

[Krzysztof Kozlowski]

On Tue, Jun 09, 2026 at 09:52:27AM +0200, Loic Poulain wrote:
> Document the NVMEM cells supported by the ath10k driver, the
> mac-address, pre-calibration data, and calibration data.
> 
> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
>  .../devicetree/bindings/net/wireless/qcom,ath10k.yaml    | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml b/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
> index c21d66c7cd558ab792524be9afec8b79272d1c87..7391df5e7071e626af4c64b9919d48c41ac09f1e 100644
> --- a/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
> +++ b/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
> @@ -92,6 +92,22 @@ properties:
>  
>    ieee80211-freq-limit: true
>  
> +  nvmem-cells:
> +    minItems: 1
> +    maxItems: 3
> +    description: |

If there is going to be resend:
Do not need '|' unless you need to preserve formatting.

> +      References to nvmem cells for MAC address and/or calibration data.
> +      Supported cell names are mac-address, calibration, and pre-calibration.
> +
> +  nvmem-cell-names:
> +    minItems: 1
> +    maxItems: 3
> +    items:
> +      enum:
> +        - mac-address
> +        - calibration
> +        - pre-calibration

This means you expect random order with variable number of items. Is
that intentional? If yes, please provide short explanation in the commit
msg.

Best regards,
Krzysztof

Re: [PATCH v4 2/8] dt-bindings: net: wireless: qcom,ath10k: Document NVMEM cells

[Loic Poulain]

On Wed, Jun 10, 2026 at 9:16 AM Krzysztof Kozlowski <krzk@kernel.org> wrote:
>
> On Tue, Jun 09, 2026 at 09:52:27AM +0200, Loic Poulain wrote:
> > Document the NVMEM cells supported by the ath10k driver, the
> > mac-address, pre-calibration data, and calibration data.
> >
> > Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> > Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> > ---
> >  .../devicetree/bindings/net/wireless/qcom,ath10k.yaml    | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml b/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
> > index c21d66c7cd558ab792524be9afec8b79272d1c87..7391df5e7071e626af4c64b9919d48c41ac09f1e 100644
> > --- a/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
> > +++ b/Documentation/devicetree/bindings/net/wireless/qcom,ath10k.yaml
> > @@ -92,6 +92,22 @@ properties:
> >
> >    ieee80211-freq-limit: true
> >
> > +  nvmem-cells:
> > +    minItems: 1
> > +    maxItems: 3
> > +    description: |
>
> If there is going to be resend:
> Do not need '|' unless you need to preserve formatting.

Sure, thanks.

>
> > +      References to nvmem cells for MAC address and/or calibration data.
> > +      Supported cell names are mac-address, calibration, and pre-calibration.
> > +
> > +  nvmem-cell-names:
> > +    minItems: 1
> > +    maxItems: 3
> > +    items:
> > +      enum:
> > +        - mac-address
> > +        - calibration
> > +        - pre-calibration
>
> This means you expect random order with variable number of items. Is
> that intentional? If yes, please provide short explanation in the commit
> msg.

Yes we may or may have any of those cells. Will document.

Thanks,
Loic

Re: [PATCH v4 2/8] dt-bindings: net: wireless: qcom,ath10k: Document NVMEM cells

[Krzysztof Kozlowski]

On 09/06/2026 09:52, Loic Poulain wrote:
> Document the NVMEM cells supported by the ath10k driver, the
> mac-address, pre-calibration data, and calibration data.
> 
> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---


Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof

Re: [PATCH v4 6/8] Bluetooth: hci_sync: Add NVMEM-backed BD address retrieval

[Dmitry Baryshkov]

On Tue, Jun 09, 2026 at 09:52:31AM +0200, Loic Poulain wrote:
> Some devices store the Bluetooth BD address in non-volatile
> memory, which can be accessed through the NVMEM framework.
> Similar to Ethernet or WiFi MAC addresses, add support for
> reading the BD address from a 'local-bd-address' NVMEM cell.
> 
> As with the device-tree provided BD address, add a quirk to
> indicate whether a device or platform should attempt to read
> the address from NVMEM when no valid in-chip address is present.
> Also add a quirk to indicate if the address is stored in
> big-endian byte order.
> 
> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
>  include/net/bluetooth/hci.h | 18 ++++++++++++++++++
>  net/bluetooth/hci_sync.c    | 39 ++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 56 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index 572b1c620c5d653a1fe10b26c1b0ba33e8f4968f..7686466d1109253b0d75edeb5f6a99fb98ce4cc6 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -164,6 +164,24 @@ enum {
>  	 */
>  	HCI_QUIRK_BDADDR_PROPERTY_BROKEN,
>  
> +	/* When this quirk is set, the public Bluetooth address
> +	 * initially reported by HCI Read BD Address command
> +	 * is considered invalid. The public BD Address can be
> +	 * retrieved via a 'local-bd-address' NVMEM cell.

Why do we need a quirk here? Can't we always assume that if there is an
NVMEM cell, it contains a correct address, even if HCI command returned
a seemingly-sensible one?

> +	 *
> +	 * This quirk can be set before hci_register_dev is called or
> +	 * during the hdev->setup vendor callback.
> +	 */
> +	HCI_QUIRK_USE_BDADDR_NVMEM,
> +
> +	/* When this quirk is set, the Bluetooth Device Address provided by
> +	 * the 'local-bd-address' NVMEM is stored in big-endian order.
> +	 *
> +	 * This quirk can be set before hci_register_dev is called or
> +	 * during the hdev->setup vendor callback.
> +	 */
> +	HCI_QUIRK_BDADDR_NVMEM_BE,

Also, is this necessary? Are the devices which store the address in the
wrong format in the NVMEM?

> +
>  	/* When this quirk is set, the duplicate filtering during
>  	 * scanning is based on Bluetooth devices addresses. To allow
>  	 * RSSI based updates, restart scanning if needed.

-- 
With best wishes
Dmitry

Re: [PATCH v4 7/8] Bluetooth: qca: Set NVMEM BD address quirks when address is invalid

[Dmitry Baryshkov]

On Tue, Jun 09, 2026 at 09:52:32AM +0200, Loic Poulain wrote:
> When the controller BD address is invalid (zero or default),
> set the NVMEM quirks to allow retrieving the address from a
> 'local-bd-address' NVMEM cell. The BD address is often stored
> alongside the WiFi MAC address in big-endian format, so also
> set the big-endian quirk.

Okay, this answers my question to the previous patch. We need to support
BE addresses.

> 
> Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> ---
>  drivers/bluetooth/btqca.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 

-- 
With best wishes
Dmitry

Re: [PATCH v4 6/8] Bluetooth: hci_sync: Add NVMEM-backed BD address retrieval

[Loic Poulain]

On Fri, Jun 12, 2026 at 11:11 AM Dmitry Baryshkov
<dmitry.baryshkov@oss.qualcomm.com> wrote:
>
> On Tue, Jun 09, 2026 at 09:52:31AM +0200, Loic Poulain wrote:
> > Some devices store the Bluetooth BD address in non-volatile
> > memory, which can be accessed through the NVMEM framework.
> > Similar to Ethernet or WiFi MAC addresses, add support for
> > reading the BD address from a 'local-bd-address' NVMEM cell.
> >
> > As with the device-tree provided BD address, add a quirk to
> > indicate whether a device or platform should attempt to read
> > the address from NVMEM when no valid in-chip address is present.
> > Also add a quirk to indicate if the address is stored in
> > big-endian byte order.
> >
> > Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> > Signed-off-by: Loic Poulain <loic.poulain@oss.qualcomm.com>
> > ---
> >  include/net/bluetooth/hci.h | 18 ++++++++++++++++++
> >  net/bluetooth/hci_sync.c    | 39 ++++++++++++++++++++++++++++++++++++++-
> >  2 files changed, 56 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> > index 572b1c620c5d653a1fe10b26c1b0ba33e8f4968f..7686466d1109253b0d75edeb5f6a99fb98ce4cc6 100644
> > --- a/include/net/bluetooth/hci.h
> > +++ b/include/net/bluetooth/hci.h
> > @@ -164,6 +164,24 @@ enum {
> >        */
> >       HCI_QUIRK_BDADDR_PROPERTY_BROKEN,
> >
> > +     /* When this quirk is set, the public Bluetooth address
> > +      * initially reported by HCI Read BD Address command
> > +      * is considered invalid. The public BD Address can be
> > +      * retrieved via a 'local-bd-address' NVMEM cell.
>
> Why do we need a quirk here? Can't we always assume that if there is an
> NVMEM cell, it contains a correct address, even if HCI command returned
> a seemingly-sensible one?

The pattern follows HCI_QUIRK_USE_BDADDR_PROPERTY, the quirk indicates
that the address returned by the HCI Read BD Address command is
invalid and should be overridden using a fwnode property. Without this
quirk, even a valid fwnode-provided address is ignored. So here this
is primarily done to align with that established behavior, although
whether that design choice is ideal is a good question.

This also raises the question of why an explicit HCI_QUIRK_USE_* flag
is required to allow reading from NVMEM when the controller-provided
address is known to be invalid, rather than attempting to use any
available backend (fwnode-prop or NVMEM). but this remains
consistent with the behavior established by the fwnode-based quirk.

So, I think these aspects could be revisited in a Bluetooth follow-up
series if there is interest in reworking the overall addr fallback
design.

Regards,
Loic



>
> > +      *
> > +      * This quirk can be set before hci_register_dev is called or
> > +      * during the hdev->setup vendor callback.
> > +      */
> > +     HCI_QUIRK_USE_BDADDR_NVMEM,
> > +
> > +     /* When this quirk is set, the Bluetooth Device Address provided by
> > +      * the 'local-bd-address' NVMEM is stored in big-endian order.
> > +      *
> > +      * This quirk can be set before hci_register_dev is called or
> > +      * during the hdev->setup vendor callback.
> > +      */
> > +     HCI_QUIRK_BDADDR_NVMEM_BE,
>
> Also, is this necessary? Are the devices which store the address in the
> wrong format in the NVMEM?
>
> > +
> >       /* When this quirk is set, the duplicate filtering during
> >        * scanning is based on Bluetooth devices addresses. To allow
> >        * RSSI based updates, restart scanning if needed.
>
> --
> With best wishes
> Dmitry