regmap: Add support for padding between register and address

Some devices, especially those with high speed control interfaces, require
padding between the register and the data. Support this in the regmap API
by providing a pad_bits configuration parameter.

Only devices with integer byte counts are supported.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/internal.h

@@ -22,6 +22,7 @@ struct regcache_ops;
 struct regmap_format {
 	size_t buf_size;
 	size_t reg_bytes;
+	size_t pad_bytes;
 	size_t val_bytes;
 	void (*format_write)(struct regmap *map,
 			     unsigned int reg, unsigned int val);

drivers/base/regmap/regmap.c

@@ -160,7 +160,9 @@ struct regmap *regmap_init(struct device *dev,
 	mutex_init(&map->lock);
 	map->format.buf_size = (config->reg_bits + config->val_bits) / 8;
 	map->format.reg_bytes = config->reg_bits / 8;
+	map->format.pad_bytes = config->pad_bits / 8;
 	map->format.val_bytes = config->val_bits / 8;
+	map->format.buf_size += map->format.pad_bytes;
 	map->dev = dev;
 	map->bus = bus;
 	map->max_register = config->max_register;
@@ -235,7 +237,7 @@ struct regmap *regmap_init(struct device *dev,
 	    !(map->format.format_reg && map->format.format_val))
 		goto err_map;
 
-	map->work_buf = kmalloc(map->format.buf_size, GFP_KERNEL);
+	map->work_buf = kzalloc(map->format.buf_size, GFP_KERNEL);
 	if (map->work_buf == NULL) {
 		ret = -ENOMEM;
 		goto err_map;
@@ -329,23 +331,28 @@ static int _regmap_raw_write(struct regmap *map, unsigned int reg,
 	 * send the work_buf directly, otherwise try to do a gather
 	 * write.
 	 */
-	if (val == map->work_buf + map->format.reg_bytes)
+	if (val == (map->work_buf + map->format.pad_bytes +
+		    map->format.reg_bytes))
 		ret = map->bus->write(map->dev, map->work_buf,
-				      map->format.reg_bytes + val_len);
+				      map->format.reg_bytes +
+				      map->format.pad_bytes +
+				      val_len);
 	else if (map->bus->gather_write)
 		ret = map->bus->gather_write(map->dev, map->work_buf,
-					     map->format.reg_bytes,
+					     map->format.reg_bytes +
+					     map->format.pad_bytes,
 					     val, val_len);
 
 	/* If that didn't work fall back on linearising by hand. */
 	if (ret == -ENOTSUPP) {
-		len = map->format.reg_bytes + val_len;
-		buf = kmalloc(len, GFP_KERNEL);
+		len = map->format.reg_bytes + map->format.pad_bytes + val_len;
+		buf = kzalloc(len, GFP_KERNEL);
 		if (!buf)
 			return -ENOMEM;
 
 		memcpy(buf, map->work_buf, map->format.reg_bytes);
-		memcpy(buf + map->format.reg_bytes, val, val_len);
+		memcpy(buf + map->format.reg_bytes + map->format.pad_bytes,
+		       val, val_len);
 		ret = map->bus->write(map->dev, buf, len);
 
 		kfree(buf);
@@ -387,10 +394,12 @@ int _regmap_write(struct regmap *map, unsigned int reg,
 
 		return ret;
 	} else {
-		map->format.format_val(map->work_buf + map->format.reg_bytes,
-				       val);
+		map->format.format_val(map->work_buf + map->format.reg_bytes
+				       + map->format.pad_bytes, val);
 		return _regmap_raw_write(map, reg,
-					 map->work_buf + map->format.reg_bytes,
+					 map->work_buf +
+					 map->format.reg_bytes +
+					 map->format.pad_bytes,
 					 map->format.val_bytes);
 	}
 }
@@ -473,7 +482,8 @@ static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 	trace_regmap_hw_read_start(map->dev, reg,
 				   val_len / map->format.val_bytes);
 
-	ret = map->bus->read(map->dev, map->work_buf, map->format.reg_bytes,
+	ret = map->bus->read(map->dev, map->work_buf,
+			     map->format.reg_bytes + map->format.pad_bytes,
 			     val, val_len);
 
 	trace_regmap_hw_read_done(map->dev, reg,

include/linux/regmap.h

@@ -44,6 +44,7 @@ struct reg_default {
  * Configuration for the register map of a device.
  *
  * @reg_bits: Number of bits in a register address, mandatory.
+ * @pad_bits: Number of bits of padding between register and value.
  * @val_bits: Number of bits in a register value, mandatory.
  *
  * @writeable_reg: Optional callback returning true if the register
@@ -74,6 +75,7 @@ struct reg_default {
  */
 struct regmap_config {
 	int reg_bits;
+	int pad_bits;
 	int val_bits;
 
 	bool (*writeable_reg)(struct device *dev, unsigned int reg);