regmap: Add provisions to have user-defined read operation

This commit is a preparatory commit to provide "no-bus" configuration
option for regmap API. It adds necessary plumbing needed to have the
ability to provide user define register read function.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/internal.h

@@ -74,6 +74,8 @@ struct regmap {
 	const struct regmap_access_table *volatile_table;
 	const struct regmap_access_table *precious_table;
 
+	int (*reg_read)(void *context, unsigned int reg, unsigned int *val);
+
 	u8 read_flag_mask;
 	u8 write_flag_mask;
 

drivers/base/regmap/regmap.c

@@ -34,6 +34,9 @@ static int _regmap_update_bits(struct regmap *map, unsigned int reg,
 			       unsigned int mask, unsigned int val,
 			       bool *change);
 
+static int _regmap_bus_read(void *context, unsigned int reg,
+			    unsigned int *val);
+
 bool regmap_reg_in_ranges(unsigned int reg,
 			  const struct regmap_range *ranges,
 			  unsigned int nranges)
@@ -430,6 +433,8 @@ struct regmap *regmap_init(struct device *dev,
 		map->read_flag_mask = bus->read_flag_mask;
 	}
 
+	map->reg_read = _regmap_bus_read;
+
 	reg_endian = config->reg_format_endian;
 	if (reg_endian == REGMAP_ENDIAN_DEFAULT)
 		reg_endian = bus->reg_format_endian_default;
@@ -1202,10 +1207,27 @@ static int _regmap_raw_read(struct regmap *map, unsigned int reg, void *val,
 	return ret;
 }
 
+static int _regmap_bus_read(void *context, unsigned int reg,
+			    unsigned int *val)
+{
+	int ret;
+	struct regmap *map = context;
+
+	if (!map->format.parse_val)
+		return -EINVAL;
+
+	ret = _regmap_raw_read(map, reg, map->work_buf, map->format.val_bytes);
+	if (ret == 0)
+		*val = map->format.parse_val(map->work_buf);
+
+	return ret;
+}
+
 static int _regmap_read(struct regmap *map, unsigned int reg,
 			unsigned int *val)
 {
 	int ret;
+	BUG_ON(!map->reg_read);
 
 	if (!map->cache_bypass) {
 		ret = regcache_read(map, reg, val);
@@ -1213,26 +1235,21 @@ static int _regmap_read(struct regmap *map, unsigned int reg,
 			return 0;
 	}
 
-	if (!map->format.parse_val)
-		return -EINVAL;
-
 	if (map->cache_only)
 		return -EBUSY;
 
-	ret = _regmap_raw_read(map, reg, map->work_buf, map->format.val_bytes);
+	ret = map->reg_read(map, reg, val);
 	if (ret == 0) {
-		*val = map->format.parse_val(map->work_buf);
-
 #ifdef LOG_DEVICE
 		if (strcmp(dev_name(map->dev), LOG_DEVICE) == 0)
 			dev_info(map->dev, "%x => %x\n", reg, *val);
 #endif
 
 		trace_regmap_reg_read(map->dev, reg, *val);
-	}
 
-	if (ret == 0 && !map->cache_bypass)
-		regcache_write(map, reg, *val);
+		if (!map->cache_bypass)
+			regcache_write(map, reg, *val);
+	}
 
 	return ret;
 }