debugfs: Add support to print u32 array in debugfs

Move the code from Xen to debugfs to make the code common
for other users as well.

Accked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Suzuki Poulose <suzuki@in.ibm.com>
[v1: Fixed rebase issues]
[v2: Fixed PPC compile issues]
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 128 insertions, 0 deletions

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 5dfafdd1dbd3..2340f6978d6e 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -20,6 +20,7 @@
 #include <linux/namei.h>
 #include <linux/debugfs.h>
 #include <linux/io.h>
+#include <linux/slab.h>
 
 static ssize_t default_read_file(struct file *file, char __user *buf,
                                  size_t count, loff_t *ppos)
@@ -520,6 +521,133 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode,
 }
 EXPORT_SYMBOL_GPL(debugfs_create_blob);
 
+struct array_data {
+        void *array;
+        u32 elements;
+};
+
+static int u32_array_open(struct inode *inode, struct file *file)
+{
+        file->private_data = NULL;
+        return nonseekable_open(inode, file);
+}
+
+static size_t format_array(char *buf, size_t bufsize, const char *fmt,
+                           u32 *array, u32 array_size)
+{
+        size_t ret = 0;
+        u32 i;
+
+        for (i = 0; i < array_size; i++) {
+                size_t len;
+
+                len = snprintf(buf, bufsize, fmt, array[i]);
+                len++;  /* ' ' or '\n' */
+                ret += len;
+
+                if (buf) {
+                        buf += len;
+                        bufsize -= len;
+                        buf[-1] = (i == array_size-1) ? '\n' : ' ';
+                }
+        }
+
+        ret++;          /* \0 */
+        if (buf)
+                *buf = '\0';
+
+        return ret;
+}
+
+static char *format_array_alloc(const char *fmt, u32 *array,
+                                                u32 array_size)
+{
+        size_t len = format_array(NULL, 0, fmt, array, array_size);
+        char *ret;
+
+        ret = kmalloc(len, GFP_KERNEL);
+        if (ret == NULL)
+                return NULL;
+
+        format_array(ret, len, fmt, array, array_size);
+        return ret;
+}
+
+static ssize_t u32_array_read(struct file *file, char __user *buf, size_t len,
+                              loff_t *ppos)
+{
+        struct inode *inode = file->f_path.dentry->d_inode;
+        struct array_data *data = inode->i_private;
+        size_t size;
+
+        if (*ppos == 0) {
+                if (file->private_data) {
+                        kfree(file->private_data);
+                        file->private_data = NULL;
+                }
+
+                file->private_data = format_array_alloc("%u", data->array,
+                                                              data->elements);
+        }
+
+        size = 0;
+        if (file->private_data)
+                size = strlen(file->private_data);
+
+        return simple_read_from_buffer(buf, len, ppos,
+                                        file->private_data, size);
+}
+
+static int u32_array_release(struct inode *inode, struct file *file)
+{
+        kfree(file->private_data);
+
+        return 0;
+}
+
+static const struct file_operations u32_array_fops = {
+        .owner   = THIS_MODULE,
+        .open    = u32_array_open,
+        .release = u32_array_release,
+        .read    = u32_array_read,
+        .llseek  = no_llseek,
+};
+
+/**
+ * debugfs_create_u32_array - create a debugfs file that is used to read u32
+ * array.
+ * @name: a pointer to a string containing the name of the file to create.
+ * @mode: the permission that the file should have.
+ * @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.
+ * @array: u32 array that provides data.
+ * @elements: total number of elements in the array.
+ *
+ * This function creates a file in debugfs with the given name that exports
+ * @array as data. If the @mode variable is so set it can be read from.
+ * Writing is not supported. Seek within the file is also not supported.
+ * Once array is created its size can not be changed.
+ *
+ * The function returns a pointer to dentry on success. If debugfs is not
+ * enabled in the kernel, the value -%ENODEV will be returned.
+ */
+struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
+                                            struct dentry *parent,
+                                            u32 *array, u32 elements)
+{
+        struct array_data *data = kmalloc(sizeof(*data), GFP_KERNEL);
+
+        if (data == NULL)
+                return NULL;
+
+        data->array = array;
+        data->elements = elements;
+
+        return debugfs_create_file(name, mode, parent, data, &u32_array_fops);
+}
+EXPORT_SYMBOL_GPL(debugfs_create_u32_array);
+
 #ifdef CONFIG_HAS_IOMEM
 
 /*