[PATCH v6 7/7] mtd: ubi: provide NVMEM layer over UBI volumes
Daniel Golle
daniel at makrotopia.org
Sun Dec 17 14:20:16 PST 2023
In an ideal world we would like UBI to be used where ever possible on a
NAND chip. And with UBI support in ARM Trusted Firmware and U-Boot it
is possible to achieve an (almost-)all-UBI flash layout. Hence the need
for a way to also use UBI volumes to store board-level constants, such
as MAC addresses and calibration data of wireless interfaces.
Add UBI volume NVMEM driver module exposing UBI volumes as NVMEM
providers. Allow UBI devices to have a "volumes" firmware subnode with
volumes which may be compatible with "nvmem-cells".
Access to UBI volumes via the NVMEM interface at this point is
read-only, and it is slow, opening and closing the UBI volume for each
access due to limitations of the NVMEM provider API.
Signed-off-by: Daniel Golle <daniel at makrotopia.org>
---
drivers/mtd/ubi/Kconfig | 12 +++
drivers/mtd/ubi/Makefile | 1 +
drivers/mtd/ubi/nvmem.c | 188 +++++++++++++++++++++++++++++++++++++++
3 files changed, 201 insertions(+)
create mode 100644 drivers/mtd/ubi/nvmem.c
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 2ed77b7b3fcb5..45d939bbfa853 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -104,4 +104,16 @@ config MTD_UBI_BLOCK
If in doubt, say "N".
+config MTD_UBI_NVMEM
+ tristate "UBI virtual NVMEM"
+ default n
+ depends on NVMEM
+ help
+ This option enabled an additional driver exposing UBI volumes as NVMEM
+ providers, intended for platforms where UBI is part of the firmware
+ specification and used to store also e.g. MAC addresses or board-
+ specific Wi-Fi calibration data.
+
+ If in doubt, say "N".
+
endif # MTD_UBI
diff --git a/drivers/mtd/ubi/Makefile b/drivers/mtd/ubi/Makefile
index 543673605ca72..4b51aaf00d1a2 100644
--- a/drivers/mtd/ubi/Makefile
+++ b/drivers/mtd/ubi/Makefile
@@ -7,3 +7,4 @@ ubi-$(CONFIG_MTD_UBI_FASTMAP) += fastmap.o
ubi-$(CONFIG_MTD_UBI_BLOCK) += block.o
obj-$(CONFIG_MTD_UBI_GLUEBI) += gluebi.o
+obj-$(CONFIG_MTD_UBI_NVMEM) += nvmem.o
diff --git a/drivers/mtd/ubi/nvmem.c b/drivers/mtd/ubi/nvmem.c
new file mode 100644
index 0000000000000..b7a93c495d172
--- /dev/null
+++ b/drivers/mtd/ubi/nvmem.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2023 Daniel Golle <daniel at makrotopia.org>
+ */
+
+/* UBI NVMEM provider */
+#include "ubi.h"
+#include <linux/nvmem-provider.h>
+#include <asm/div64.h>
+
+/* List of all NVMEM devices */
+static LIST_HEAD(nvmem_devices);
+static DEFINE_MUTEX(devices_mutex);
+
+struct ubi_nvmem {
+ struct nvmem_device *nvmem;
+ int ubi_num;
+ int vol_id;
+ int usable_leb_size;
+ struct list_head list;
+};
+
+static int ubi_nvmem_reg_read(void *priv, unsigned int from,
+ void *val, size_t bytes)
+{
+ int err = 0, lnum = from, offs, bytes_left = bytes, to_read;
+ struct ubi_nvmem *unv = priv;
+ struct ubi_volume_desc *desc;
+
+ desc = ubi_open_volume(unv->ubi_num, unv->vol_id, UBI_READONLY);
+ if (IS_ERR(desc))
+ return PTR_ERR(desc);
+
+ offs = do_div(lnum, unv->usable_leb_size);
+ while (bytes_left) {
+ to_read = unv->usable_leb_size - offs;
+
+ if (to_read > bytes_left)
+ to_read = bytes_left;
+
+ err = ubi_read(desc, lnum, val, offs, to_read);
+ if (err)
+ break;
+
+ lnum += 1;
+ offs = 0;
+ bytes_left -= to_read;
+ val += to_read;
+ }
+ ubi_close_volume(desc);
+
+ if (err)
+ return err;
+
+ return bytes_left == 0 ? 0 : -EIO;
+}
+
+static int ubi_nvmem_add(struct ubi_volume_info *vi)
+{
+ struct device_node *np = dev_of_node(vi->dev);
+ struct nvmem_config config = {};
+ struct ubi_nvmem *unv;
+ int ret;
+
+ if (!np)
+ return 0;
+
+ if (!of_get_child_by_name(np, "nvmem-layout"))
+ return 0;
+
+ if (WARN_ON_ONCE(vi->usable_leb_size <= 0) ||
+ WARN_ON_ONCE(vi->size <= 0))
+ return -EINVAL;
+
+ unv = kzalloc(sizeof(struct ubi_nvmem), GFP_KERNEL);
+ if (!unv)
+ return -ENOMEM;
+
+ config.id = NVMEM_DEVID_NONE;
+ config.dev = vi->dev;
+ config.name = dev_name(vi->dev);
+ config.owner = THIS_MODULE;
+ config.priv = unv;
+ config.reg_read = ubi_nvmem_reg_read;
+ config.size = vi->usable_leb_size * vi->size;
+ config.word_size = 1;
+ config.stride = 1;
+ config.read_only = true;
+ config.root_only = true;
+ config.ignore_wp = true;
+ config.of_node = np;
+
+ unv->ubi_num = vi->ubi_num;
+ unv->vol_id = vi->vol_id;
+ unv->usable_leb_size = vi->usable_leb_size;
+ unv->nvmem = nvmem_register(&config);
+ if (IS_ERR(unv->nvmem)) {
+ ret = dev_err_probe(vi->dev, PTR_ERR(unv->nvmem),
+ "Failed to register NVMEM device\n");
+ kfree(unv);
+ return ret;
+ }
+
+ mutex_lock(&devices_mutex);
+ list_add_tail(&unv->list, &nvmem_devices);
+ mutex_unlock(&devices_mutex);
+
+ return 0;
+}
+
+static void ubi_nvmem_remove(struct ubi_volume_info *vi)
+{
+ struct ubi_nvmem *unv_c, *unv = NULL;
+
+ mutex_lock(&devices_mutex);
+ list_for_each_entry(unv_c, &nvmem_devices, list)
+ if (unv_c->ubi_num == vi->ubi_num && unv_c->vol_id == vi->vol_id) {
+ unv = unv_c;
+ break;
+ }
+
+ if (!unv) {
+ mutex_unlock(&devices_mutex);
+ return;
+ }
+
+ list_del(&unv->list);
+ mutex_unlock(&devices_mutex);
+ nvmem_unregister(unv->nvmem);
+ kfree(unv);
+}
+
+/**
+ * nvmem_notify - UBI notification handler.
+ * @nb: registered notifier block
+ * @l: notification type
+ * @ns_ptr: pointer to the &struct ubi_notification object
+ */
+static int nvmem_notify(struct notifier_block *nb, unsigned long l,
+ void *ns_ptr)
+{
+ struct ubi_notification *nt = ns_ptr;
+
+ switch (l) {
+ case UBI_VOLUME_RESIZED:
+ ubi_nvmem_remove(&nt->vi);
+ fallthrough;
+ case UBI_VOLUME_ADDED:
+ ubi_nvmem_add(&nt->vi);
+ break;
+ case UBI_VOLUME_SHUTDOWN:
+ ubi_nvmem_remove(&nt->vi);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block nvmem_notifier = {
+ .notifier_call = nvmem_notify,
+};
+
+static int __init ubi_nvmem_init(void)
+{
+ return ubi_register_volume_notifier(&nvmem_notifier, 0);
+}
+
+static void __exit ubi_nvmem_exit(void)
+{
+ struct ubi_nvmem *unv, *tmp;
+
+ mutex_lock(&devices_mutex);
+ list_for_each_entry_safe(unv, tmp, &nvmem_devices, list) {
+ nvmem_unregister(unv->nvmem);
+ list_del(&unv->list);
+ kfree(unv);
+ }
+ mutex_unlock(&devices_mutex);
+
+ ubi_unregister_volume_notifier(&nvmem_notifier);
+}
+
+module_init(ubi_nvmem_init);
+module_exit(ubi_nvmem_exit);
+MODULE_DESCRIPTION("NVMEM layer over UBI volumes");
+MODULE_AUTHOR("Daniel Golle");
+MODULE_LICENSE("GPL");
--
2.43.0
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