[PATCH] proc: Add a way to make proc files writable

[Qingjie Xing <xqjcool@xxxxxxxxx>]

Provide an extra function, proc_create_single_write_data() that
act like its non-write version but also set a write method in
the proc_dir_entry struct. Alse provide a macro
proc_create_single_write to reduces the boilerplate code in the callers.

Signed-off-by: Qingjie Xing <xqjcool@xxxxxxxxx>
---
 fs/proc/generic.c       | 18 ++++++++++++++++++
 include/linux/proc_fs.h |  8 +++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index dbe82cf23ee4..0f32a92195fc 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -641,6 +641,7 @@ static const struct proc_ops proc_single_ops = {
 	.proc_read_iter = seq_read_iter,
 	.proc_lseek	= seq_lseek,
 	.proc_release	= single_release,
+	.proc_write	= proc_simple_write,
 };
 
 struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
@@ -658,6 +659,23 @@ struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
 }
 EXPORT_SYMBOL(proc_create_single_data);
 
+struct proc_dir_entry *proc_create_single_write_data(const char *name,
+		umode_t mode, struct proc_dir_entry *parent,
+		int (*show)(struct seq_file *, void *), proc_write_t write,
+		void *data)
+{
+	struct proc_dir_entry *p;
+
+	p = proc_create_reg(name, mode, &parent, data);
+	if (!p)
+		return NULL;
+	p->proc_ops = &proc_single_ops;
+	p->single_show = show;
+	p->write = write;
+	return proc_register(parent, p);
+}
+EXPORT_SYMBOL(proc_create_single_write_data);
+
 void proc_set_size(struct proc_dir_entry *de, loff_t size)
 {
 	de->size = size;
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 0b2a89854440..488d0b76a06f 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -102,7 +102,13 @@ struct proc_dir_entry *proc_create_single_data(const char *name, umode_t mode,
 		int (*show)(struct seq_file *, void *), void *data);
 #define proc_create_single(name, mode, parent, show) \
 	proc_create_single_data(name, mode, parent, show, NULL)
- 
+struct proc_dir_entry *proc_create_single_write_data(const char *name,
+		umode_t mode, struct proc_dir_entry *parent,
+		int (*show)(struct seq_file *, void *), proc_write_t write,
+		void *data);
+#define proc_create_single_write(name, mode, parent, show, write) \
+	proc_create_single_write_data(name, mode, parent, show, write, NULL)
+
 extern struct proc_dir_entry *proc_create_data(const char *, umode_t,
 					       struct proc_dir_entry *,
 					       const struct proc_ops *,
-- 
2.43.0