[PATCH v5 1/2] mtd: mtdcore: 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 mtd_debugfs_populate() to create two debugfs nodes
(ie. partname and partid). The upper driver can assign the pointer to
partname and partid before calling mtd_device_register().

Signed-off-by: Zhuohao Lee <zhuohao@xxxxxxxxxxxx>
---
Changes in V5:
- Move debugfs_create_dir() to mtd_debugfs_populate()
- Previous discussion: https://patchwork.ozlabs.org/patch/1107810/
Changes in V4:
- Separate the change to two patches. The first patch is adding the general
  handling for the partname and partid in the mtdcore.c. The second patch
  is enabling the two debugfs nodes for spi-nor.
- Previous discussion: https://patchwork.ozlabs.org/patch/1097377/
Changes in v3:
- Add partname and partid to mtd.h and create debugfs inside mtdcore.c
- Previous discussion: https://patchwork.ozlabs.org/patch/1095731/
Changes in v2:
- Change to use debugfs to output flash name and id
- Previous discussion: https://patchwork.ozlabs.org/patch/1067763/
---
 drivers/mtd/mtdcore.c   | 88 ++++++++++++++++++++++++++++++++++++-----
 include/linux/mtd/mtd.h |  4 ++
 2 files changed, 83 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 3ef01baef9b6..b1911c21eb1a 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -357,6 +357,84 @@ static const struct device_type mtd_devtype = {
 	.release	= mtd_release,
 };
 
+static int mtd_partid_show(struct seq_file *s, void *p)
+{
+	struct mtd_info *mtd = s->private;
+
+	if (!mtd->dbg.partid)
+		return 0;
+
+	seq_printf(s, "%s\n", mtd->dbg.partid);
+
+	return 0;
+}
+
+static int mtd_partid_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, mtd_partid_show, inode->i_private);
+}
+
+static const struct file_operations mtd_partid_debug_fops = {
+	.open           = mtd_partid_debugfs_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+static int mtd_partname_show(struct seq_file *s, void *p)
+{
+	struct mtd_info *mtd = s->private;
+
+	if (!mtd->dbg.partname)
+		return 0;
+
+	seq_printf(s, "%s\n", mtd->dbg.partname);
+
+	return 0;
+}
+
+static int mtd_partname_debugfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, mtd_partname_show, inode->i_private);
+}
+
+static const struct file_operations mtd_partname_debug_fops = {
+	.open           = mtd_partname_debugfs_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+static struct dentry *dfs_dir_mtd;
+
+static void mtd_debugfs_populate(struct mtd_info *mtd)
+{
+	struct device *dev = &mtd->dev;
+	struct dentry *root, *dent;
+
+	if (IS_ERR_OR_NULL(dfs_dir_mtd))
+		return;
+
+	root = mtd->dbg.dfs_dir = debugfs_create_dir(dev_name(dev),
+						     dfs_dir_mtd);
+	if (IS_ERR_OR_NULL(root)) {
+		pr_debug("mtd device %s won't show data in debugfs\n",
+			 dev_name(dev));
+		return;
+	}
+
+	dent = debugfs_create_file("partid", S_IRUSR, root, mtd,
+				   &mtd_partid_debug_fops);
+	if (IS_ERR_OR_NULL(dent)) {
+		pr_err("cannot create debugfs entry for partid\n");
+		return;
+	}
+	dent = debugfs_create_file("partname", S_IRUSR, root, mtd,
+				   &mtd_partname_debug_fops);
+	if (IS_ERR_OR_NULL(dent))
+		pr_err("cannot create debugfs entry for partname\n");
+}
+
 #ifndef CONFIG_MMU
 unsigned mtd_mmap_capabilities(struct mtd_info *mtd)
 {
@@ -534,8 +612,6 @@ static int mtd_nvmem_add(struct mtd_info *mtd)
 	return 0;
 }
 
-static struct dentry *dfs_dir_mtd;
-
 /**
  *	add_mtd_device - register an MTD device
  *	@mtd: pointer to new MTD device info structure
@@ -621,13 +697,7 @@ int add_mtd_device(struct mtd_info *mtd)
 	if (error)
 		goto fail_nvmem_add;
 
-	if (!IS_ERR_OR_NULL(dfs_dir_mtd)) {
-		mtd->dbg.dfs_dir = debugfs_create_dir(dev_name(&mtd->dev), dfs_dir_mtd);
-		if (IS_ERR_OR_NULL(mtd->dbg.dfs_dir)) {
-			pr_debug("mtd device %s won't show data in debugfs\n",
-				 dev_name(&mtd->dev));
-		}
-	}
+	mtd_debugfs_populate(mtd);
 
 	device_create(&mtd_class, mtd->dev.parent, MTD_DEVT(i) + 1, NULL,
 		      "mtd%dro", i);
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 677768b21a1d..c20f53c77899 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -203,6 +203,10 @@ struct module;	/* only needed for owner field in mtd_info */
  */
 struct mtd_debug_info {
 	struct dentry *dfs_dir;
+
+	/* debugfs stuff starts here */
+	const char *partname;
+	const char *partid;
 };
 
 struct mtd_info {
-- 
2.22.0.rc1.311.g5d7573a151-goog


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