[PATCH v9 2/8] mfd: simple-mfd-i2c: specify max_register

Alex Elder
2025-07-24T20:25:19Z

All devices supported by simple MFD use the same 8-bit register 8-bit
value regmap configuration. There is an option available for a device
to specify a custom configuration, but no existing device uses it.

Rather than requiring a "full" regmap configuration to be provided to
change only the max_register value, Lee Jones suggested allowing
max_register to be specified in the simple_mfd_data structure. The
8-bit register 8-bit configuration is still used by default, but
max_register is also applied if it is non-zero.

If both regmap_config and max_register are provided, the max_register
field in the regmap_config structure is ignored.

Signed-off-by: Alex Elder <elder@riscstar.com>
Suggested-by: Lee Jones <lee@kernel.org>
---
v9: - max_register takes precedence over regmap_config in simple_mfd_data
- New function simple_regmap_config() encapsulates providing config
- simple_regmap_config() allocates a regmap_config if necessary
- A small duplicated comment is removed in "simple-mfd-i2c.h"

drivers/mfd/simple-mfd-i2c.c | 38 +++++++++++++++++++++++++++++++-----
drivers/mfd/simple-mfd-i2c.h | 5 +----
2 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/drivers/mfd/simple-mfd-i2c.c b/drivers/mfd/simple-mfd-i2c.c
index 22159913bea03..f3ba79c112d4e 100644
--- a/drivers/mfd/simple-mfd-i2c.c
+++ b/drivers/mfd/simple-mfd-i2c.c
@@ -29,6 +29,36 @@ static const struct regmap_config regmap_config_8r_8v = {
.val_bits = 8,
};

+/*
+ * Determine regmap config to use. If no regmap_config is provided,
+ * regmap_config_8r_8v is used. If max_register is specified it is
+ * (also) used, whether or not regmap_config is provided.
+ */
+static const struct regmap_config *
+simple_regmap_config(struct device *dev, const struct simple_mfd_data *data)
+{
+ struct regmap_config *regmap_config;
+
+ if (!data)
+ return &regmap_config_8r_8v;
+
+ if (data->regmap_config && !data->max_register)
+ return data->regmap_config;
+
+ regmap_config = devm_kzalloc(dev, sizeof(*regmap_config), GFP_KERNEL);
+ if (!regmap_config)
+ return NULL;
+
+ if (data->regmap_config)
+ *regmap_config = *data->regmap_config;
+ else
+ *regmap_config = regmap_config_8r_8v;
+ if (data->max_register)
+ regmap_config->max_register = data->max_register;
+
+ return regmap_config;
+}
+
static int simple_mfd_i2c_probe(struct i2c_client *i2c)
{
const struct simple_mfd_data *simple_mfd_data;
@@ -38,11 +68,9 @@ static int simple_mfd_i2c_probe(struct i2c_client *i2c)

simple_mfd_data = device_get_match_data(&i2c->dev);

- /* If no regmap_config is specified, use the default 8reg and 8val bits */
- if (!simple_mfd_data || !simple_mfd_data->regmap_config)
- regmap_config = &regmap_config_8r_8v;
- else
- regmap_config = simple_mfd_data->regmap_config;
+ regmap_config = simple_regmap_config(&i2c->dev, simple_mfd_data);
+ if (!regmap_config)
+ return -ENOMEM;

regmap = devm_regmap_init_i2c(i2c, regmap_config);
if (IS_ERR(regmap))
diff --git a/drivers/mfd/simple-mfd-i2c.h b/drivers/mfd/simple-mfd-i2c.h
index 7cb2bdd347d97..6fa36b3d7a217 100644
--- a/drivers/mfd/simple-mfd-i2c.h
+++ b/drivers/mfd/simple-mfd-i2c.h
@@ -8,10 +8,6 @@
* shared by all sub-devices. Children can use their parent's device structure
* (dev.parent) in order to reference it.
*
- * This driver creates a single register map with the intention for it to be
- * shared by all sub-devices. Children can use their parent's device structure
- * (dev.parent) in order to reference it.
- *
* Once the register map has been successfully initialised, any sub-devices
* represented by child nodes in Device Tree or via the MFD cells in the
* associated C file will be subsequently registered.
@@ -25,6 +21,7 @@

struct simple_mfd_data {
const struct regmap_config *regmap_config;
+ unsigned int max_register;
const struct mfd_cell *mfd_cell;
size_t mfd_cell_size;
};
--
2.43.0