regmap: implement register striding

regmap_config.reg_stride is introduced. All extant register addresses
are a multiple of this value. Users of serial-oriented regmap busses will
typically set this to 1. Users of the MMIO regmap bus will typically set
this based on the value size of their registers, in bytes, so 4 for a
32-bit register.

Throughout the regmap code, actual register addresses are used. Wherever
the register address is used to index some array of values, the address
is divided by the stride to determine the index, or vice-versa. Error-
checking is added to all entry-points for register address data to ensure
that register addresses actually satisfy the specified stride. The MMIO
bus ensures that the specified stride is large enough for the register
size.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 680ddd7de60e..0258bcd6258d 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -50,6 +50,9 @@ struct reg_default {
  *        register regions.
  *
  * @reg_bits: Number of bits in a register address, mandatory.
+ * @reg_stride: The register address stride. Valid register addresses are a
+ *              multiple of this value. If set to 0, a value of 1 will be
+ *              used.
  * @pad_bits: Number of bits of padding between register and value.
  * @val_bits: Number of bits in a register value, mandatory.
  *
@@ -83,6 +86,7 @@ struct regmap_config {
 	const char *name;
 
 	int reg_bits;
+	int reg_stride;
 	int pad_bits;
 	int val_bits;