Re: [PATCH 2/3] mtd: Add support for reading MTD devices via the nvmem API
From: Srinivas Kandagatla
Date: Fri Mar 03 2017 - 06:24:59 EST
On 02/03/17 19:50, Alban wrote:
Allow drivers that use the nvmem API to read data stored on MTD devices.
This add a simple mtd user that register itself as a read-only nvmem
device.
Good stuff!! and useful for MAC addresses.
Am not going to repeat the same comments as Boris, but I totally agree
with his comments.
Signed-off-by: Alban <albeu@xxxxxxx>
---
drivers/mtd/Kconfig | 9 ++++
drivers/mtd/Makefile | 1 +
drivers/mtd/mtdnvmem.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 131 insertions(+)
create mode 100644 drivers/mtd/mtdnvmem.c
May be we should move this driver to drivers/nvmem/
diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
index e83a279..9cad86c 100644
--- a/drivers/mtd/Kconfig
+++ b/drivers/mtd/Kconfig
@@ -322,6 +322,15 @@ config MTD_PARTITIONED_MASTER
the parent of the partition device be the master device, rather than
what lies behind the master.
+config MTD_NVMEM
+ tristate "Read config data from MTD devices"
May be..
"Read config data from MTD devices via NVMEM API".
Or
"MTD NVMEM Provider"
+ default y
Do you really want it be ON by default?
+ depends on NVMEM
Adding COMPILE_TEST would give us good test coverage.
+ help
+ Provides support for reading config data from MTD devices. This can
+ be used by drivers to read device specific data such as MAC addresses
+ or calibration results.
+
source "drivers/mtd/chips/Kconfig"
source "drivers/mtd/maps/Kconfig"
diff --git a/drivers/mtd/Makefile b/drivers/mtd/Makefile
index 99bb9a1..f62f50b 100644
--- a/drivers/mtd/Makefile
+++ b/drivers/mtd/Makefile
@@ -26,6 +26,7 @@ obj-$(CONFIG_SSFDC) += ssfdc.o
obj-$(CONFIG_SM_FTL) += sm_ftl.o
obj-$(CONFIG_MTD_OOPS) += mtdoops.o
obj-$(CONFIG_MTD_SWAP) += mtdswap.o
+obj-$(CONFIG_MTD_NVMEM) += mtdnvmem.o
nftl-objs := nftlcore.o nftlmount.o
inftl-objs := inftlcore.o inftlmount.o
diff --git a/drivers/mtd/mtdnvmem.c b/drivers/mtd/mtdnvmem.c
new file mode 100644
index 0000000..6eb4216
--- /dev/null
+++ b/drivers/mtd/mtdnvmem.c
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2017 Alban Bedel <albeu@xxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/nvmem-provider.h>
+#include <linux/nvmem-consumer.h>
??
+#include <linux/slab.h>
+#include <linux/of.h>
+
+struct mtd_nvmem {
+ struct list_head list;
+ struct mtd_info *mtd;
+ struct nvmem_device *nvmem;
+};
+
+static DEFINE_MUTEX(mtd_nvmem_list_lock);
+static LIST_HEAD(mtd_nvmem_list);
+
+static int mtd_nvmem_reg_read(void *priv, unsigned int offset,
+ void *val, size_t bytes)
+{
+ struct mtd_info *mtd = priv;
+ size_t retlen;
+ int err;
+
+ err = mtd_read(mtd, offset, bytes, &retlen, val);
+ if (err && err != -EUCLEAN)
+ return err;
+
+ return retlen == bytes ? 0 : -EIO;
+}
+
+static void mtd_nvmem_add(struct mtd_info *mtd)
+{
+ struct device *dev = &mtd->dev;
+ struct device_node *np = dev_of_node(dev);
+ struct nvmem_config config = {};
+ struct mtd_nvmem *mtd_nvmem;
+
+ /* OF devices have to provide the nvmem node */
+ if (np && !of_property_read_bool(np, "nvmem-provider"))
+ return;
we should prefix the property with mtd to make to more explicit that
this is very much specific to MTD.
+
+ config.dev = dev;
+ config.owner = THIS_MODULE;
+ config.reg_read = mtd_nvmem_reg_read;
+ config.size = mtd->size;
+ config.word_size = 1;
+ config.stride = 1;
+ config.read_only = true;
+ config.priv = mtd;
+
+ /* Alloc our struct to keep track of the MTD NVMEM devices */
+ mtd_nvmem = kzalloc(sizeof(*mtd_nvmem), GFP_KERNEL);
+ if (!mtd_nvmem)
+ return;
+
+ mtd_nvmem->mtd = mtd;
+ mtd_nvmem->nvmem = nvmem_register(&config);
+ if (IS_ERR(mtd_nvmem->nvmem)) {
+ dev_err(dev, "Failed to register NVMEM device\n");
+ kfree(mtd_nvmem);
+ return;
+ }
+
+ mutex_lock(&mtd_nvmem_list_lock);
+ list_add_tail(&mtd_nvmem->list, &mtd_nvmem_list);
+ mutex_unlock(&mtd_nvmem_list_lock);
+}
+
+static void mtd_nvmem_remove(struct mtd_info *mtd)
+{
+ struct mtd_nvmem *mtd_nvmem;
+ bool found = false;
+
May be we can use of_nvmem_find() directly here and avoid all this list
and lock thingy. It should make the driver much simpler.
Am sure we can add exception to make of_nvmem_find() symbol public if
its helping providers like this.
+ mutex_lock(&mtd_nvmem_list_lock);
+ list_for_each_entry(mtd_nvmem, &mtd_nvmem_list, list) {
+ if (mtd_nvmem->mtd == mtd) {
+ list_del(&mtd_nvmem->list);
+ found = true;
+ break;
+ }
+ }
+ mutex_unlock(&mtd_nvmem_list_lock);
+
+ if (found) {
+ if (nvmem_unregister(mtd_nvmem->nvmem))
+ dev_err(&mtd->dev,
+ "Failed to unregister NVMEM device\n");
I will be nice to feedback error to top layer, as it does not make sense
to remove providers if there are active consumers using it.
del_mtd_device(), unregister_mtd_user() have return values, I see no
reason why notifiers should not return errors.
May be if we should fix the remove() call backs to handle and return errors.
+ kfree(mtd_nvmem);
+ }
+}
+
+static struct mtd_notifier mtd_nvmem_notifier = {
+ .add = mtd_nvmem_add,
+ .remove = mtd_nvmem_remove,
+};
+
+static int __init mtd_nvmem_init(void)
+{
+ register_mtd_user(&mtd_nvmem_notifier);
+ return 0;
+}
+module_init(mtd_nvmem_init);
+
+static void __exit mtd_nvmem_exit(void)
+{
+ unregister_mtd_user(&mtd_nvmem_notifier);
+}
+module_exit(mtd_nvmem_exit);
+
+MODULE_LICENSE("GPL");
GPL V2 ??
Thanks,
srini
+MODULE_AUTHOR("Alban Bedel <albeu@xxxxxxx>");
+MODULE_DESCRIPTION("Driver to read config data from MTD devices");