From 935e8c4b1315f00254d0de40608b772e97132440 Mon Sep 17 00:00:00 2001
From: Bram Vlerick <bram.vlerick@openpixelsystems.org>
Date: Thu, 11 Apr 2024 11:30:13 +0200
Subject: [PATCH] i2c: target: eeprom_target: add address_width parameter

Add a parameter to allow the configuration of the number of address
bytes used by the I2C master. This allows the driver to expose larger
buffer sizes.

Tested with standard linux at24 driver.

Signed-off-by: Bram Vlerick <bram.vlerick@openpixelsystems.org>
---
 drivers/i2c/target/eeprom_target.c            | 22 +++++++++++++------
 .../mtd/zephyr,i2c-target-eeprom.yaml         |  8 +++++++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/target/eeprom_target.c b/drivers/i2c/target/eeprom_target.c
index 8cef8ea2553..19953ec5559 100644
--- a/drivers/i2c/target/eeprom_target.c
+++ b/drivers/i2c/target/eeprom_target.c
@@ -22,7 +22,8 @@ struct i2c_eeprom_target_data {
 	uint32_t buffer_size;
 	uint8_t *buffer;
 	uint32_t buffer_idx;
-	bool first_write;
+	uint32_t idx_write_cnt;
+	uint8_t address_width;
 };
 
 struct i2c_eeprom_target_config {
@@ -86,7 +87,7 @@ static int eeprom_target_write_requested(struct i2c_target_config *config)
 
 	LOG_DBG("eeprom: write req");
 
-	data->first_write = true;
+	data->idx_write_cnt = 0;
 
 	return 0;
 }
@@ -121,9 +122,13 @@ static int eeprom_target_write_received(struct i2c_target_config *config,
 	 * I2C controller support
 	 */
 
-	if (data->first_write) {
-		data->buffer_idx = val;
-		data->first_write = false;
+	if (data->idx_write_cnt < (data->address_width >> 3)) {
+		if (data->idx_write_cnt == 0) {
+			data->buffer_idx = 0;
+		}
+
+		data->buffer_idx = val | (data->buffer_idx << 8);
+		data->idx_write_cnt++;
 	} else {
 		data->buffer[data->buffer_idx++] = val;
 	}
@@ -162,7 +167,7 @@ static int eeprom_target_stop(struct i2c_target_config *config)
 
 	LOG_DBG("eeprom: stop");
 
-	data->first_write = true;
+	data->idx_write_cnt = 0;
 
 	return 0;
 }
@@ -246,7 +251,10 @@ static int i2c_eeprom_target_init(const struct device *dev)
 
 #define I2C_EEPROM_INIT(inst)						\
 	static struct i2c_eeprom_target_data				\
-		i2c_eeprom_target_##inst##_dev_data;			\
+		i2c_eeprom_target_##inst##_dev_data = {			\
+			.address_width = DT_INST_PROP_OR(inst,		\
+					address_width, 8),		\
+		};							\
 									\
 	static uint8_t							\
 	i2c_eeprom_target_##inst##_buffer[(DT_INST_PROP(inst, size))];	\
diff --git a/dts/bindings/mtd/zephyr,i2c-target-eeprom.yaml b/dts/bindings/mtd/zephyr,i2c-target-eeprom.yaml
index c6dcfbfec52..ff465b8cef4 100644
--- a/dts/bindings/mtd/zephyr,i2c-target-eeprom.yaml
+++ b/dts/bindings/mtd/zephyr,i2c-target-eeprom.yaml
@@ -5,3 +5,11 @@ description: Zephyr I2C target EEPROM
 compatible: "zephyr,i2c-target-eeprom"
 
 include: ["eeprom-base.yaml", i2c-device.yaml]
+
+properties:
+  address-width:
+    type: int
+    enum: [8, 16]
+    description: |
+      Number of address bits used to address the EEPROM. If not specified
+      the EEPROM is assumed to have a 8-bit address.