linux-kernel - [PATCH v9 2/8] mfd: simple-mfd-i2c: specify max

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Message-ID: <20250724202511.499288-3-elder@riscstar.com>
Date: Thu, 24 Jul 2025 15:25:03 -0500
From: Alex Elder <elder@...cstar.com>
To: lee@...nel.org,
	lgirdwood@...il.com,
	broonie@...nel.org,
	alexandre.belloni@...tlin.com,
	robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org
Cc: mat.jonczyk@...pl,
	dlan@...too.org,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr,
	linux.amoon@...il.com,
	troymitchell988@...il.com,
	guodong@...cstar.com,
	linux-rtc@...r.kernel.org,
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Subject: [PATCH v9 2/8] mfd: simple-mfd-i2c: specify max_register

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@...cstar.com>
Suggested-by: Lee Jones <lee@...nel.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