[RFC PATCH 6/6] block: implement NVMEM provider
Daniel Golle
daniel at makrotopia.org
Wed Jul 19 15:04:17 PDT 2023
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 at makrotopia.org>
---
block/Kconfig | 8 ++
block/Makefile | 1 +
block/blk-nvmem.c | 187 ++++++++++++++++++++++++++++++++++++++++
block/blk.h | 13 +++
block/genhd.c | 2 +
block/partitions/core.c | 2 +
6 files changed, 213 insertions(+)
create mode 100644 block/blk-nvmem.c
diff --git a/block/Kconfig b/block/Kconfig
index 86122e459fe04..185573877964d 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -218,6 +218,14 @@ config BLK_MQ_VIRTIO
config BLK_PM
def_bool PM
+config BLK_NVMEM
+ bool "Block device NVMEM provider"
+ depends on OF
+ help
+ Allow block devices (or partitions) to act as NVMEM prodivers,
+ typically using if an eMMC is used to store MAC addresses or Wi-Fi
+ calibration data on embedded devices.
+
# do not use in new code
config BLOCK_HOLDER_DEPRECATED
bool
diff --git a/block/Makefile b/block/Makefile
index 46ada9dc8bbfe..03c0bfa8642df 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_BLK_DEV_ZONED) += blk-zoned.o
obj-$(CONFIG_BLK_WBT) += blk-wbt.o
obj-$(CONFIG_BLK_DEBUG_FS) += blk-mq-debugfs.o
obj-$(CONFIG_BLK_DEBUG_FS_ZONED)+= blk-mq-debugfs-zoned.o
+obj-$(CONFIG_BLK_NVMEM) += blk-nvmem.o
obj-$(CONFIG_BLK_SED_OPAL) += sed-opal.o
obj-$(CONFIG_BLK_PM) += blk-pm.o
obj-$(CONFIG_BLK_INLINE_ENCRYPTION) += blk-crypto.o blk-crypto-profile.o \
diff --git a/block/blk-nvmem.c b/block/blk-nvmem.c
new file mode 100644
index 0000000000000..8238511049f56
--- /dev/null
+++ b/block/blk-nvmem.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * block device NVMEM provider
+ *
+ * Copyright (c) 2023 Daniel Golle <daniel at makrotopia.org>
+ *
+ * Useful on devices using a partition on an eMMC for MAC addresses or
+ * Wi-Fi calibration EEPROM data.
+ */
+
+#include "blk.h"
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/pagemap.h>
+#include <linux/property.h>
+
+/* List of all NVMEM devices */
+static LIST_HEAD(nvmem_devices);
+static DEFINE_MUTEX(devices_mutex);
+
+struct blk_nvmem {
+ struct nvmem_device *nvmem;
+ struct block_device *bdev;
+ struct list_head list;
+};
+
+static int blk_nvmem_reg_read(void *priv, unsigned int from,
+ void *val, size_t bytes)
+{
+ pgoff_t f_index = from >> PAGE_SHIFT;
+ struct address_space *mapping;
+ struct blk_nvmem *bnv = priv;
+ size_t bytes_left = bytes;
+ struct folio *folio;
+ unsigned long offs, to_read;
+ void *p;
+
+ if (!bnv->bdev)
+ return -ENODEV;
+
+ offs = from & ((1 << PAGE_SHIFT) - 1);
+ mapping = bnv->bdev->bd_inode->i_mapping;
+
+ while (bytes_left) {
+ folio = read_mapping_folio(mapping, f_index++, NULL);
+ if (IS_ERR(folio))
+ return PTR_ERR(folio);
+
+ to_read = min_t(unsigned long, bytes_left, PAGE_SIZE - offs);
+ p = folio_address(folio) + offset_in_folio(folio, offs);
+ memcpy(val, p, to_read);
+ offs = 0;
+ bytes_left -= to_read;
+ val += to_read;
+ folio_put(folio);
+ }
+
+ return bytes_left == 0 ? 0 : -EIO;
+}
+
+void blk_register_nvmem(struct block_device *bdev)
+{
+ struct fwnode_handle *fw_parts = NULL, *fw_part_c, *fw_part = NULL;
+ struct nvmem_config config = {};
+ const char *partname, *uuid;
+ struct device *dev, *p0dev;
+ struct blk_nvmem *bnv;
+ u32 reg;
+
+ /*
+ * skip devices which set GENHD_FL_NO_NVMEM
+ *
+ * This flag is used for mtdblock and ubiblock devices because
+ * both, MTD and UBI already implement their own NVMEM provider.
+ * To avoid registering multiple NVMEM providers for the same
+ * device node, skip the block NVMEM provider.
+ */
+ if (bdev->bd_disk->flags & GENHD_FL_NO_NVMEM)
+ return;
+
+ /* skip too large devices */
+ if (bdev_nr_bytes(bdev) > INT_MAX)
+ return;
+
+ dev = &bdev->bd_device;
+ if (!bdev_is_partition(bdev)) {
+ fw_part = dev->fwnode;
+
+ if (!fw_part && dev->parent)
+ fw_part = dev->parent->fwnode;
+
+ goto no_parts;
+ }
+
+ p0dev = &bdev->bd_disk->part0->bd_device;
+ fw_parts = device_get_named_child_node(p0dev, "partitions");
+ if (!fw_parts)
+ fw_parts = device_get_named_child_node(p0dev->parent, "partitions");
+
+ if (!fw_parts)
+ return;
+
+ fwnode_for_each_child_node(fw_parts, fw_part_c) {
+ if (!fwnode_property_read_string(fw_part_c, "uuid", &uuid) &&
+ (!bdev->bd_meta_info || strncmp(uuid,
+ bdev->bd_meta_info->uuid,
+ PARTITION_META_INFO_UUIDLTH)))
+ continue;
+
+ if (!fwnode_property_read_string(fw_part_c, "partname", &partname) &&
+ (!bdev->bd_meta_info || strncmp(partname,
+ bdev->bd_meta_info->volname,
+ PARTITION_META_INFO_VOLNAMELTH)))
+ continue;
+
+ /*
+ * partition addresses (reg) in device tree greater than
+ * DISK_MAX_PARTS can be used to match uuid or partname only
+ */
+ if (!fwnode_property_read_u32(fw_part_c, "reg", ®) &&
+ reg < DISK_MAX_PARTS && bdev->bd_partno != reg)
+ continue;
+
+ fw_part = fw_part_c;
+ break;
+ }
+
+no_parts:
+ if (!fwnode_device_is_compatible(fw_part, "nvmem-cells"))
+ return;
+
+ bnv = kzalloc(sizeof(struct blk_nvmem), GFP_KERNEL);
+ if (!bnv)
+ return;
+
+ config.id = NVMEM_DEVID_NONE;
+ config.dev = &bdev->bd_device;
+ config.name = dev_name(&bdev->bd_device);
+ config.owner = THIS_MODULE;
+ config.priv = bnv;
+ 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(fw_part);
+
+ bnv->bdev = bdev;
+ bnv->nvmem = nvmem_register(&config);
+ if (IS_ERR(bnv->nvmem)) {
+ /* Just ignore if there is no NVMEM support in the kernel */
+ if (PTR_ERR(bnv->nvmem) != -EOPNOTSUPP)
+ dev_err_probe(&bdev->bd_device, PTR_ERR(bnv->nvmem),
+ "Failed to register NVMEM device\n");
+
+ kfree(bnv);
+ return;
+ }
+
+ mutex_lock(&devices_mutex);
+ list_add_tail(&bnv->list, &nvmem_devices);
+ mutex_unlock(&devices_mutex);
+}
+
+void blk_unregister_nvmem(struct block_device *bdev)
+{
+ struct blk_nvmem *bnv_c, *bnv = NULL;
+
+ mutex_lock(&devices_mutex);
+ list_for_each_entry(bnv_c, &nvmem_devices, list)
+ if (bnv_c->bdev == bdev) {
+ bnv = bnv_c;
+ break;
+ }
+
+ if (!bnv) {
+ mutex_unlock(&devices_mutex);
+ return;
+ }
+
+ list_del(&bnv->list);
+ mutex_unlock(&devices_mutex);
+ nvmem_unregister(bnv->nvmem);
+ kfree(bnv);
+}
diff --git a/block/blk.h b/block/blk.h
index 686712e138352..7423d0d5494e9 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -515,4 +515,17 @@ static inline int req_ref_read(struct request *req)
return atomic_read(&req->ref);
}
+#ifdef CONFIG_BLK_NVMEM
+void blk_register_nvmem(struct block_device *bdev);
+void blk_unregister_nvmem(struct block_device *bdev);
+#else
+static inline void blk_register_nvmem(struct block_device *bdev)
+{
+}
+
+static inline void blk_unregister_nvmem(struct block_device *bdev)
+{
+}
+#endif
+
#endif /* BLK_INTERNAL_H */
diff --git a/block/genhd.c b/block/genhd.c
index 3d287b32d50df..b306e0f407bb2 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -527,6 +527,7 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
disk_update_readahead(disk);
disk_add_events(disk);
set_bit(GD_ADDED, &disk->state);
+ blk_register_nvmem(disk->part0);
return 0;
out_unregister_bdi:
@@ -569,6 +570,7 @@ static void blk_report_disk_dead(struct gendisk *disk)
if (bdev->bd_holder_ops && bdev->bd_holder_ops->mark_dead)
bdev->bd_holder_ops->mark_dead(bdev);
mutex_unlock(&bdev->bd_holder_lock);
+ blk_unregister_nvmem(bdev);
put_device(&bdev->bd_device);
rcu_read_lock();
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 13a7341299a91..68bd655f5e68e 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -404,6 +404,8 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
/* suppress uevent if the disk suppresses it */
if (!dev_get_uevent_suppress(ddev))
kobject_uevent(&pdev->kobj, KOBJ_ADD);
+
+ blk_register_nvmem(bdev);
return bdev;
out_del:
--
2.41.0
More information about the linux-mtd
mailing list