[PATCH v2] mtd: spi-nor: add debugfs nodes for querying the flash name and id

[Zhuohao Lee <zhuohao@xxxxxxxxxxxx>]

Currently, we don't have vfs nodes for querying the underlying
flash name and flash id. This information is important especially
when we want to know the flash detail of the defective system.
In order to support the query, we add a function spi_nor_debugfs_create()
to create the debugfs node (ie. flashname and flashid)
This patch is modified based on the SPI-NOR flash system as we
only have the SPI-NOR system now. But the idea should be applied to
the other flash driver like NAND flash.

The output of new debugfs nodes on my device are:
cat /sys/kernel/debug/mtd/mtd0/flashid
ef6017
cat /sys/kernel/debug/mtd/mtd0/flashname
w25q64dw

Signed-off-by: Zhuohao Lee <zhuohao@xxxxxxxxxxxx>
---
 drivers/mtd/devices/m25p80.c  |  5 ++-
 drivers/mtd/spi-nor/spi-nor.c | 62 +++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h   |  6 ++++
 3 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index c4a1d04b8c80..be11e7d96646 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -231,8 +231,11 @@ static int m25p_probe(struct spi_mem *spimem)
 	if (ret)
 		return ret;
 
-	return mtd_device_register(&nor->mtd, data ? data->parts : NULL,
+	ret = mtd_device_register(&nor->mtd, data ? data->parts : NULL,
 				   data ? data->nr_parts : 0);
+	if (!ret)
+		spi_nor_debugfs_create(nor);
+	return ret;
 }
 
 
diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index 6e13bbd1aaa5..004b6adf5866 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -21,6 +21,8 @@
 #include <linux/of_platform.h>
 #include <linux/spi/flash.h>
 #include <linux/mtd/spi-nor.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 
 /* Define max times to check status register before we give up. */
 
@@ -4161,6 +4163,66 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 }
 EXPORT_SYMBOL_GPL(spi_nor_scan);
 
+static int flashid_dbg_show(struct seq_file *s, void *p)
+{
+	struct spi_nor *nor = (struct spi_nor *)s->private;
+	const struct flash_info *info = nor->info;
+
+	if (!info->id_len)
+		return 0;
+	seq_printf(s, "%*phN\n", info->id_len, info->id);
+	return 0;
+}
+
+static int flashid_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, flashid_dbg_show, inode->i_private);
+}
+
+static const struct file_operations flashid_dbg_fops = {
+	.open		= flashid_debugfs_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static int flashname_dbg_show(struct seq_file *s, void *p)
+{
+	struct spi_nor *nor = (struct spi_nor *)s->private;
+	const struct flash_info *info = nor->info;
+
+	if (!info->name)
+		return 0;
+	seq_printf(s, "%s\n", info->name);
+	return 0;
+}
+
+static int flashname_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, flashname_dbg_show, inode->i_private);
+}
+
+static const struct file_operations flashname_dbg_fops = {
+	.open		= flashname_debugfs_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+void spi_nor_debugfs_create(struct spi_nor *nor)
+{
+	struct mtd_info *mtd = &nor->mtd;
+	struct dentry *root = mtd->dbg.dfs_dir;
+
+	if (IS_ERR_OR_NULL(root) || IS_ERR_OR_NULL(nor)) {
+		return;
+	}
+	debugfs_create_file("flashid", S_IRUSR, root, nor,
+			&flashid_dbg_fops);
+	debugfs_create_file("flashname", S_IRUSR, root, nor,
+			&flashname_dbg_fops);
+}
+
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Huang Shijie <shijie8@xxxxxxxxx>");
 MODULE_AUTHOR("Mike Lavender");
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index fa2d89e38e40..eadb5230c6d0 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -530,4 +530,10 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
  */
 void spi_nor_restore(struct spi_nor *nor);
 
+/**
+ * spi_nor_debugfs_create() - create debug fs
+ * @mtd:	the spi_nor structure
+ */
+void spi_nor_debugfs_create(struct spi_nor *nor);
+
 #endif
-- 
2.21.0.1020.gf2820cf01a-goog


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