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-rw-r--r--fs/libfs.c100
1 files changed, 100 insertions, 0 deletions
diff --git a/fs/libfs.c b/fs/libfs.c
index f90b295..5025563 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -519,6 +519,102 @@ int simple_transaction_release(struct inode *inode, struct file *file)
return 0;
}
+/* Simple attribute files */
+
+struct simple_attr {
+ u64 (*get)(void *);
+ void (*set)(void *, u64);
+ char get_buf[24]; /* enough to store a u64 and "\n\0" */
+ char set_buf[24];
+ void *data;
+ const char *fmt; /* format for read operation */
+ struct semaphore sem; /* protects access to these buffers */
+};
+
+/* simple_attr_open is called by an actual attribute open file operation
+ * to set the attribute specific access operations. */
+int simple_attr_open(struct inode *inode, struct file *file,
+ u64 (*get)(void *), void (*set)(void *, u64),
+ const char *fmt)
+{
+ struct simple_attr *attr;
+
+ attr = kmalloc(sizeof(*attr), GFP_KERNEL);
+ if (!attr)
+ return -ENOMEM;
+
+ attr->get = get;
+ attr->set = set;
+ attr->data = inode->u.generic_ip;
+ attr->fmt = fmt;
+ init_MUTEX(&attr->sem);
+
+ file->private_data = attr;
+
+ return nonseekable_open(inode, file);
+}
+
+int simple_attr_close(struct inode *inode, struct file *file)
+{
+ kfree(file->private_data);
+ return 0;
+}
+
+/* read from the buffer that is filled with the get function */
+ssize_t simple_attr_read(struct file *file, char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ struct simple_attr *attr;
+ size_t size;
+ ssize_t ret;
+
+ attr = file->private_data;
+
+ if (!attr->get)
+ return -EACCES;
+
+ down(&attr->sem);
+ if (*ppos) /* continued read */
+ size = strlen(attr->get_buf);
+ else /* first read */
+ size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
+ attr->fmt,
+ (unsigned long long)attr->get(attr->data));
+
+ ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
+ up(&attr->sem);
+ return ret;
+}
+
+/* interpret the buffer as a number to call the set function with */
+ssize_t simple_attr_write(struct file *file, const char __user *buf,
+ size_t len, loff_t *ppos)
+{
+ struct simple_attr *attr;
+ u64 val;
+ size_t size;
+ ssize_t ret;
+
+ attr = file->private_data;
+
+ if (!attr->set)
+ return -EACCES;
+
+ down(&attr->sem);
+ ret = -EFAULT;
+ size = min(sizeof(attr->set_buf) - 1, len);
+ if (copy_from_user(attr->set_buf, buf, size))
+ goto out;
+
+ ret = len; /* claim we got the whole input */
+ attr->set_buf[size] = '\0';
+ val = simple_strtol(attr->set_buf, NULL, 0);
+ attr->set(attr->data, val);
+out:
+ up(&attr->sem);
+ return ret;
+}
+
EXPORT_SYMBOL(dcache_dir_close);
EXPORT_SYMBOL(dcache_dir_lseek);
EXPORT_SYMBOL(dcache_dir_open);
@@ -547,3 +643,7 @@ EXPORT_SYMBOL(simple_read_from_buffer);
EXPORT_SYMBOL(simple_transaction_get);
EXPORT_SYMBOL(simple_transaction_read);
EXPORT_SYMBOL(simple_transaction_release);
+EXPORT_SYMBOL_GPL(simple_attr_open);
+EXPORT_SYMBOL_GPL(simple_attr_close);
+EXPORT_SYMBOL_GPL(simple_attr_read);
+EXPORT_SYMBOL_GPL(simple_attr_write);
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