linux-kernel - [PATCH 1/2] debugfs: support read-only and write-only bool types

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Message-Id: <1433514886-11884-2-git-send-email-rf@opensource.wolfsonmicro.com>
Date:	Fri,  5 Jun 2015 15:34:45 +0100
From:	Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
To:	gregkh@...uxfoundation.org, broonie@...nel.org
Cc:	linux-kernel@...r.kernel.org, patches@...nsource.wolfsonmicro.com
Subject: [PATCH 1/2] debugfs: support read-only and write-only bool types

The various integer functions support read-only and write-only
versions so extend this to bool types.

Signed-off-by: Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
---
 fs/debugfs/file.c |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 830a7e7..7dc3f8a 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -43,6 +43,18 @@ const struct file_operations debugfs_file_operations = {
 	.llseek =	noop_llseek,
 };
 
+static ssize_t debugs_read_wo_file(struct file *file, char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	return -EACCES;
+}
+
+static ssize_t debugs_write_ro_file(struct file *file, const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	return -EACCES;
+}
+
 static void *debugfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	nd_set_link(nd, d_inode(dentry)->i_private);
@@ -488,6 +500,20 @@ static const struct file_operations fops_bool = {
 	.llseek =	default_llseek,
 };
 
+static const struct file_operations fops_bool_ro = {
+	.read =		read_file_bool,
+	.write =	debugs_write_ro_file,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+static const struct file_operations fops_bool_wo = {
+	.read =		debugs_read_wo_file,
+	.write =	write_file_bool,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
 /**
  * debugfs_create_bool - create a debugfs file that is used to read and write a boolean value
  * @name: a pointer to a string containing the name of the file to create.
@@ -515,6 +541,15 @@ static const struct file_operations fops_bool = {
 struct dentry *debugfs_create_bool(const char *name, umode_t mode,
 				   struct dentry *parent, u32 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value,
+					   &fops_bool_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value,
+					   &fops_bool_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_bool);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_bool);
-- 
1.7.2.5

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