From: Daniel Golle <[email protected]> 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.
To safely defer the freeing of the provider private data until all consumers have released their cells, a nvmem_dev() accessor is added to the NVMEM core to expose the struct device embedded in struct nvmem_device. This allows registering a devm action on the nvmem device itself, ensuring the private data outlives any active cell references. Signed-off-by: Daniel Golle <[email protected]> Co-developed-by: Loic Poulain <[email protected]> Signed-off-by: Loic Poulain <[email protected]> --- block/Kconfig | 9 ++ block/Makefile | 1 + block/blk-nvmem.c | 188 +++++++++++++++++++++++++++++++++++++++++ drivers/nvmem/core.c | 13 +++ include/linux/nvmem-consumer.h | 6 ++ 5 files changed, 217 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..96c0ffc51b1862a75644f3f94add35d59577d86b --- /dev/null +++ b/block/blk-nvmem.c @@ -0,0 +1,188 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * block device NVMEM provider + * + * Copyright (c) 2024 Daniel Golle <[email protected]> + * + * 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/nvmem-consumer.h> +#include <linux/of.h> +#include <linux/pagemap.h> +#include <linux/property.h> + +static void blk_nvmem_free(void *data) +{ + kfree(data); +} + +/* List of all NVMEM devices */ +static LIST_HEAD(nvmem_devices); +static DEFINE_MUTEX(devices_mutex); + +struct blk_nvmem { + struct nvmem_device *nvmem; + dev_t devt; + bool removed; + struct list_head list; +}; + +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; + unsigned long offs = from & ~PAGE_MASK, to_read; + pgoff_t f_index = from >> PAGE_SHIFT; + struct blk_nvmem *bnv = priv; + size_t bytes_left = bytes; + struct file *bdev_file; + struct folio *folio; + void *p; + int ret = 0; + + if (bnv->removed) + return -ENODEV; + + bdev_file = bdev_file_open_by_dev(bnv->devt, mode, priv, NULL); + if (!bdev_file) + return -ENODEV; + + if (IS_ERR(bdev_file)) + return PTR_ERR(bdev_file); + + while (bytes_left) { + folio = read_mapping_folio(bdev_file->f_mapping, f_index++, NULL); + if (IS_ERR(folio)) { + ret = PTR_ERR(folio); + goto err_release_bdev; + } + 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); + } + +err_release_bdev: + fput(bdev_file); + + return ret; +} + +static int blk_nvmem_register(struct device *dev) +{ + struct device_node *np = dev_of_node(dev); + struct block_device *bdev = dev_to_bdev(dev); + struct nvmem_config config = {}; + struct blk_nvmem *bnv; + + /* skip devices which do not have a device tree node */ + if (!np) + return 0; + + /* skip devices without an nvmem layout defined */ + if (!of_get_child_by_name(np, "nvmem-layout")) + return 0; + + /* + * skip block device too large to be represented as NVMEM devices + * which are using an 'int' as address + */ + if (bdev_nr_bytes(bdev) > INT_MAX) + return -EFBIG; + + bnv = kzalloc_obj(*bnv); + if (!bnv) + return -ENOMEM; + + 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(dev->fwnode); + + bnv->devt = bdev->bd_device.devt; + bnv->nvmem = nvmem_register(&config); + if (IS_ERR(bnv->nvmem)) { + dev_err_probe(&bdev->bd_device, PTR_ERR(bnv->nvmem), + "Failed to register NVMEM device\n"); + + kfree(bnv); + return PTR_ERR(bnv->nvmem); + } + + /* + * Free bnv only when the nvmem device is fully released (i.e. when + * its kref hits zero), not at unregister time. This prevents a + * use-after-free if a consumer still holds an nvmem_cell reference + * when the block device is removed: nvmem_unregister() only does a + * kref_put(), so reg_read could still be called with bnv as priv + * until the last consumer drops its cell. + */ + if (devm_add_action(nvmem_dev(bnv->nvmem), blk_nvmem_free, bnv)) { + nvmem_unregister(bnv->nvmem); + kfree(bnv); + return -ENOMEM; + } + + mutex_lock(&devices_mutex); + list_add_tail(&bnv->list, &nvmem_devices); + mutex_unlock(&devices_mutex); + + return 0; +} + +static void blk_nvmem_unregister(struct device *dev) +{ + struct blk_nvmem *bnv_c, *bnv = NULL; + + mutex_lock(&devices_mutex); + list_for_each_entry(bnv_c, &nvmem_devices, list) { + if (bnv_c->devt == dev_to_bdev(dev)->bd_device.devt) { + bnv = bnv_c; + break; + } + } + + if (!bnv) { + mutex_unlock(&devices_mutex); + return; + } + + list_del(&bnv->list); + mutex_unlock(&devices_mutex); + bnv->removed = true; + nvmem_unregister(bnv->nvmem); +} + +static struct class_interface blk_nvmem_bus_interface __refdata = { + .class = &block_class, + .add_dev = &blk_nvmem_register, + .remove_dev = &blk_nvmem_unregister, +}; + +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); diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index 311cb2e5a5c02d2c6979d7c9bbb7f94abdfbdad1..ee3481229c20b3063c86d0dd66aabbf6b5e29169 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -2154,6 +2154,19 @@ const char *nvmem_dev_name(struct nvmem_device *nvmem) } EXPORT_SYMBOL_GPL(nvmem_dev_name); +/** + * nvmem_dev() - Get the struct device of a given nvmem device. + * + * @nvmem: nvmem device. + * + * Return: pointer to the struct device of the nvmem device. + */ +struct device *nvmem_dev(struct nvmem_device *nvmem) +{ + return &nvmem->dev; +} +EXPORT_SYMBOL_GPL(nvmem_dev); + /** * nvmem_dev_size() - Get the size of a given nvmem device. * diff --git a/include/linux/nvmem-consumer.h b/include/linux/nvmem-consumer.h index 34c0e58dfa26636d2804fcc7e0bc4a875ee73dae..ce387c89dc8e4bc1241f3b6f36be8c6c95e282ed 100644 --- a/include/linux/nvmem-consumer.h +++ b/include/linux/nvmem-consumer.h @@ -82,6 +82,7 @@ int nvmem_device_cell_write(struct nvmem_device *nvmem, const char *nvmem_dev_name(struct nvmem_device *nvmem); size_t nvmem_dev_size(struct nvmem_device *nvmem); +struct device *nvmem_dev(struct nvmem_device *nvmem); void nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries); @@ -220,6 +221,11 @@ static inline const char *nvmem_dev_name(struct nvmem_device *nvmem) return NULL; } +static inline struct device *nvmem_dev(struct nvmem_device *nvmem) +{ + return NULL; +} + static inline void nvmem_add_cell_lookups(struct nvmem_cell_lookup *entries, size_t nentries) {} static inline void -- 2.34.1
