regmap: debugfs: Add a registers `range' file

This file lists the register ranges in the register map.  The condition
to split the range is based on whether the block is readable or not.

Ensure that we lock the `debugfs_off_cache' list whenever we access
and modify the list.  There is a possible race otherwise between the
read() operations of the `registers' file and the `range' file.

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/internal.h

@@ -76,6 +76,7 @@ struct regmap {
 	unsigned int debugfs_tot_len;
 
 	struct list_head debugfs_off_cache;
+	struct mutex cache_lock;
 #endif
 
 	unsigned int max_register;

drivers/base/regmap/regmap-debugfs.c

@@ -88,6 +88,7 @@ static unsigned int regmap_debugfs_get_dump_start(struct regmap *map,
 	 * If we don't have a cache build one so we don't have to do a
 	 * linear scan each time.
 	 */
+	mutex_lock(&map->cache_lock);
 	i = base;
 	if (list_empty(&map->debugfs_off_cache)) {
 		for (; i <= map->max_register; i += map->reg_stride) {
@@ -110,6 +111,7 @@ static unsigned int regmap_debugfs_get_dump_start(struct regmap *map,
 				c = kzalloc(sizeof(*c), GFP_KERNEL);
 				if (!c) {
 					regmap_debugfs_free_dump_cache(map);
+					mutex_unlock(&map->cache_lock);
 					return base;
 				}
 				c->min = p;
@@ -142,12 +144,14 @@ static unsigned int regmap_debugfs_get_dump_start(struct regmap *map,
 			fpos_offset = from - c->min;
 			reg_offset = fpos_offset / map->debugfs_tot_len;
 			*pos = c->min + (reg_offset * map->debugfs_tot_len);
+			mutex_unlock(&map->cache_lock);
 			return c->base_reg + reg_offset;
 		}
 
 		*pos = c->max;
 		ret = c->max_reg;
 	}
+	mutex_unlock(&map->cache_lock);
 
 	return ret;
 }
@@ -308,6 +312,79 @@ static const struct file_operations regmap_range_fops = {
 	.llseek = default_llseek,
 };
 
+static ssize_t regmap_reg_ranges_read_file(struct file *file,
+					   char __user *user_buf, size_t count,
+					   loff_t *ppos)
+{
+	struct regmap *map = file->private_data;
+	struct regmap_debugfs_off_cache *c;
+	loff_t p = 0;
+	size_t buf_pos = 0;
+	char *buf;
+	char *entry;
+	int ret;
+
+	if (*ppos < 0 || !count)
+		return -EINVAL;
+
+	buf = kmalloc(count, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	entry = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!entry) {
+		kfree(buf);
+		return -ENOMEM;
+	}
+
+	/* While we are at it, build the register dump cache
+	 * now so the read() operation on the `registers' file
+	 * can benefit from using the cache.  We do not care
+	 * about the file position information that is contained
+	 * in the cache, just about the actual register blocks */
+	regmap_calc_tot_len(map, buf, count);
+	regmap_debugfs_get_dump_start(map, 0, *ppos, &p);
+
+	/* Reset file pointer as the fixed-format of the `registers'
+	 * file is not compatible with the `range' file */
+	p = 0;
+	mutex_lock(&map->cache_lock);
+	list_for_each_entry(c, &map->debugfs_off_cache, list) {
+		snprintf(entry, PAGE_SIZE, "%x-%x",
+			 c->base_reg, c->max_reg);
+		if (p >= *ppos) {
+			if (buf_pos + 1 + strlen(entry) > count)
+				break;
+			snprintf(buf + buf_pos, count - buf_pos,
+				 "%s", entry);
+			buf_pos += strlen(entry);
+			buf[buf_pos] = '\n';
+			buf_pos++;
+		}
+		p += strlen(entry) + 1;
+	}
+	mutex_unlock(&map->cache_lock);
+
+	kfree(entry);
+	ret = buf_pos;
+
+	if (copy_to_user(user_buf, buf, buf_pos)) {
+		ret = -EFAULT;
+		goto out_buf;
+	}
+
+	*ppos += buf_pos;
+out_buf:
+	kfree(buf);
+	return ret;
+}
+
+static const struct file_operations regmap_reg_ranges_fops = {
+	.open = simple_open,
+	.read = regmap_reg_ranges_read_file,
+	.llseek = default_llseek,
+};
+
 static ssize_t regmap_access_read_file(struct file *file,
 				       char __user *user_buf, size_t count,
 				       loff_t *ppos)
@@ -382,6 +459,7 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 	struct regmap_range_node *range_node;
 
 	INIT_LIST_HEAD(&map->debugfs_off_cache);
+	mutex_init(&map->cache_lock);
 
 	if (name) {
 		map->debugfs_name = kasprintf(GFP_KERNEL, "%s-%s",
@@ -400,6 +478,9 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 	debugfs_create_file("name", 0400, map->debugfs,
 			    map, &regmap_name_fops);
 
+	debugfs_create_file("range", 0400, map->debugfs,
+			    map, &regmap_reg_ranges_fops);
+
 	if (map->max_register) {
 		debugfs_create_file("registers", 0400, map->debugfs,
 				    map, &regmap_map_fops);
@@ -432,7 +513,9 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 void regmap_debugfs_exit(struct regmap *map)
 {
 	debugfs_remove_recursive(map->debugfs);
+	mutex_lock(&map->cache_lock);
 	regmap_debugfs_free_dump_cache(map);
+	mutex_unlock(&map->cache_lock);
 	kfree(map->debugfs_name);
 }