regmap: new API regmap_multi_reg_write() definition

New API regmap_multi_reg_write() is defined that allows a set of reg,val
pairs to be written to a I2C client device as one block transfer from the
point of view of a single I2C master system.

A simple demonstration implementation is included that just splits the
block write request into a sequence of single register writes.

The implementation will be modified later to support those I2C clients
that implement the alternative non-standard MULTIWRITE block write mode
so to achieve a single I2C transfer that will be atomic even in multiple
I2C master systems.

Signed-off-by: Anthony Olech <anthony.olech.opensource@diasemi.com>
Signed-off-by: David Dajun Chen <david.chen@diasemi.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

2 files changed, 43 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 7d689a15c500..c42ad69e527f 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -1439,6 +1439,47 @@ out:
 }
 EXPORT_SYMBOL_GPL(regmap_bulk_write);
 
+/*
+ * regmap_multi_reg_write(): Write multiple registers to the device
+ *
+ * where the set of register are supplied in any order
+ *
+ * @map: Register map to write to
+ * @regs: Array of structures containing register,value to be written
+ * @num_regs: Number of registers to write
+ *
+ * This function is intended to be used for writing a large block of data
+ * atomically to the device in single transfer for those I2C client devices
+ * that implement this alternative block write mode.
+ *
+ * A value of zero will be returned on success, a negative errno will
+ * be returned in error cases.
+ */
+int regmap_multi_reg_write(struct regmap *map, struct reg_default *regs,
+                                int num_regs)
+{
+        int ret = 0, i;
+
+        for (i = 0; i < num_regs; i++) {
+                int reg = regs[i].reg;
+                if (reg % map->reg_stride)
+                        return -EINVAL;
+        }
+
+        map->lock(map->lock_arg);
+
+        for (i = 0; i < num_regs; i++) {
+                ret = _regmap_write(map, regs[i].reg, regs[i].def);
+                if (ret != 0)
+                        goto out;
+        }
+out:
+        map->unlock(map->lock_arg);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(regmap_multi_reg_write);
+
 /**
  * regmap_raw_write_async(): Write raw values to one or more registers
  *                           asynchronously
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index a10380bfbeac..4b933a31f84f 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -378,6 +378,8 @@ int regmap_raw_write(struct regmap *map, unsigned int reg,
                      const void *val, size_t val_len);
 int regmap_bulk_write(struct regmap *map, unsigned int reg, const void *val,
                         size_t val_count);
+int regmap_multi_reg_write(struct regmap *map, struct reg_default *regs,
+                        int num_regs);
 int regmap_raw_write_async(struct regmap *map, unsigned int reg,
                            const void *val, size_t val_len);
 int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val);