Re: [PATCH] debugfs: add helper function to create device related seq_file

From: Arend van Spriel
Date: Sat Oct 11 2014 - 12:10:15 EST


On 10/11/14 18:01, Arend van Spriel wrote:
This patch adds a helper function that simplifies adding a
sequence file for device drivers. The calling device driver
needs to provide a read function and a device pointer. The
field struct seq_file::private will reference the device
pointer upon call to the read function so the driver can
obtain his data from it and do its seq_printf() calls.

Maybe should have made this RFC first. Anyways, it is intended for 3.19, although I don't mind if it would end up in 3.18 :-p

Regards,
Arend

Signed-off-by: Arend van Spriel<arend@xxxxxxxxxxxx>
---
fs/debugfs/file.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/debugfs.h | 16 ++++++++++++++-
2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 76c08c2..088b3fc 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -22,6 +22,7 @@
#include<linux/io.h>
#include<linux/slab.h>
#include<linux/atomic.h>
+#include<linux/device.h>

static ssize_t default_read_file(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
@@ -761,3 +762,56 @@ struct dentry *debugfs_create_regset32(const char *name, umode_t mode,
EXPORT_SYMBOL_GPL(debugfs_create_regset32);

#endif /* CONFIG_HAS_IOMEM */
+
+struct debugfs_devm_entry {
+ int (*read)(struct seq_file *seq, void *data);
+ struct device *dev;
+};
+
+static int debugfs_devm_entry_open(struct inode *inode, struct file *f)
+{
+ struct debugfs_devm_entry *entry = inode->i_private;
+
+ return single_open(f, entry->read, entry->dev);
+}
+
+static const struct file_operations debugfs_devm_entry_ops = {
+ .owner = THIS_MODULE,
+ .open = debugfs_devm_entry_open,
+ .release = single_release,
+ .read = seq_read,
+ .llseek = seq_lseek
+};
+
+/**
+ * debugfs_create_devm_seqfile - create a debugfs file that is bound to device.
+ *
+ * @dev: device related to this debugfs file.
+ * @name: name of the debugfs file.
+ * @parent: a pointer to the parent dentry for this file. This should be a
+ * directory dentry if set. If this parameter is %NULL, then the
+ * file will be created in the root of the debugfs filesystem.
+ * @read_fn: function pointer called to print the seq_file content.
+ */
+struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
+ struct dentry *parent,
+ int (*read_fn)(struct seq_file *s,
+ void *data))
+{
+ struct debugfs_devm_entry *entry;
+
+ if (IS_ERR(parent))
+ return ERR_PTR(-ENOENT);
+
+ entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return ERR_PTR(-ENOMEM);
+
+ entry->read = read_fn;
+ entry->dev = dev;
+
+ return debugfs_create_file(name, S_IRUGO, parent, entry,
+ &debugfs_devm_entry_ops);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_devm_seqfile);
+
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 4d0b4d1..f8c0db4 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -99,13 +99,18 @@ struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent,
u32 *array, u32 elements);

+struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
+ struct dentry *parent,
+ int (*read_fn)(struct seq_file *s,
+ void *data));
+
bool debugfs_initialized(void);

#else

#include<linux/err.h>

-/*
+/*
* We do not return NULL from these functions if CONFIG_DEBUG_FS is not enabled
* so users have a chance to detect if there was a real error or not. We don't
* want to duplicate the design decision mistakes of procfs and devfs again.
@@ -251,6 +256,15 @@ static inline struct dentry *debugfs_create_u32_array(const char *name, umode_t
return ERR_PTR(-ENODEV);
}

+static inline struct dentry *debugfs_create_devm_seqfile(struct device *dev,
+ const char *name,
+ struct dentry *parent,
+ int (*read_fn)(struct seq_file *s,
+ void *data))
+{
+ return ERR_PTR(-ENODEV);
+}
+
#endif

#endif

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