From 8da61f24cc4a4a66ecae69aa9b9aa8fd989a8969 Mon Sep 17 00:00:00 2001
From: Mark Brown <broonie@kernel.org>
Date: Tue, 20 Oct 2015 15:40:59 +0100
Subject: [PATCH] regmap: debugfs: Use seq_file for the access map

Unlike the registers file we don't have any substantial performance
concerns rendering the entire file (it involves no device accesses) so
just use seq_printf() to simplify the code.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/base/regmap/regmap-debugfs.c | 69 ++++++++--------------------
 1 file changed, 18 insertions(+), 51 deletions(-)

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index 3f0a7e262d69..1ee3d40861c7 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -397,72 +397,39 @@ static const struct file_operations regmap_reg_ranges_fops = {
 	.llseek = default_llseek,
 };
 
-static ssize_t regmap_access_read_file(struct file *file,
-				       char __user *user_buf, size_t count,
-				       loff_t *ppos)
+static int regmap_access_show(struct seq_file *s, void *ignored)
 {
-	int reg_len, tot_len;
-	size_t buf_pos = 0;
-	loff_t p = 0;
-	ssize_t ret;
-	int i;
-	struct regmap *map = file->private_data;
-	char *buf;
-
-	if (*ppos < 0 || !count)
-		return -EINVAL;
+	struct regmap *map = s->private;
+	int i, reg_len;
 
-	buf = kmalloc(count, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	/* Calculate the length of a fixed format  */
 	reg_len = regmap_calc_reg_len(map->max_register);
-	tot_len = reg_len + 10; /* ': R W V P\n' */
 
 	for (i = 0; i <= map->max_register; i += map->reg_stride) {
 		/* Ignore registers which are neither readable nor writable */
 		if (!regmap_readable(map, i) && !regmap_writeable(map, i))
 			continue;
 
-		/* If we're in the region the user is trying to read */
-		if (p >= *ppos) {
-			/* ...but not beyond it */
-			if (buf_pos + tot_len + 1 >= count)
-				break;
-
-			/* Format the register */
-			snprintf(buf + buf_pos, count - buf_pos,
-				 "%.*x: %c %c %c %c\n",
-				 reg_len, i,
-				 regmap_readable(map, i) ? 'y' : 'n',
-				 regmap_writeable(map, i) ? 'y' : 'n',
-				 regmap_volatile(map, i) ? 'y' : 'n',
-				 regmap_precious(map, i) ? 'y' : 'n');
-
-			buf_pos += tot_len;
-		}
-		p += tot_len;
-	}
-
-	ret = buf_pos;
-
-	if (copy_to_user(user_buf, buf, buf_pos)) {
-		ret = -EFAULT;
-		goto out;
+		/* Format the register */
+		seq_printf(s, "%.*x: %c %c %c %c\n", reg_len, i,
+			   regmap_readable(map, i) ? 'y' : 'n',
+			   regmap_writeable(map, i) ? 'y' : 'n',
+			   regmap_volatile(map, i) ? 'y' : 'n',
+			   regmap_precious(map, i) ? 'y' : 'n');
 	}
 
-	*ppos += buf_pos;
+	return 0;
+}
 
-out:
-	kfree(buf);
-	return ret;
+static int access_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, regmap_access_show, inode->i_private);
 }
 
 static const struct file_operations regmap_access_fops = {
-	.open = simple_open,
-	.read = regmap_access_read_file,
-	.llseek = default_llseek,
+	.open		= access_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
 };
 
 static ssize_t regmap_cache_only_write_file(struct file *file,
-- 
2.20.1