eeprom: at2x: Add support for at24cXX

drivers/eeprom/eeprom_at2x.c

@@ -92,7 +92,8 @@ static int eeprom_at2x_read(const struct device *dev, off_t offset, void *buf,
 {
 	const struct eeprom_at2x_config *config = dev->config;
 	struct eeprom_at2x_data *data = dev->data;
-	int err;
+	uint8_t *pbuf = buf;
+	int ret;
 
 	if (!len) {
 		return 0;
@@ -104,14 +105,21 @@ static int eeprom_at2x_read(const struct device *dev, off_t offset, void *buf,
 	}
 
 	k_mutex_lock(&data->lock, K_FOREVER);
-	err = config->read_fn(dev, offset, buf, len);
-	k_mutex_unlock(&data->lock);
+	while (len) {
+		ret = config->read_fn(dev, offset, pbuf, len);
+		if (ret < 0) {
+			LOG_ERR("failed to read EEPROM (err %d)", ret);
+			k_mutex_unlock(&data->lock);
+			return ret;
+		}
 
-	if (err) {
-		LOG_ERR("failed to read EEPROM (err %d)", err);
-		return err;
+		pbuf += ret;
+		offset += ret;
+		len -= ret;
 	}
 
+	k_mutex_unlock(&data->lock);
+
 	return 0;
 }
 
@@ -201,29 +209,66 @@ static size_t eeprom_at2x_size(const struct device *dev)
 }
 
 #ifdef CONFIG_EEPROM_AT24
+
+/**
+ * @brief translate an offset to a device address / offset pair
+ *
+ * It allows to address several devices as a continuous memory region
+ * but also to address higher part of eeprom for chips
+ * with more than 2^(addr_width) adressable word.
+ */
+static uint16_t eeprom_at24_translate_offset(const struct device *dev,
+					     off_t *offset)
+{
+	const struct eeprom_at2x_config *config = dev->config;
+
+	const uint16_t addr_incr = *offset >> config->addr_width;
+	*offset &= BIT_MASK(config->addr_width);
+
+	return config->bus_addr + addr_incr;
+}
+
+static size_t eeprom_at24_adjust_read_count(const struct device *dev,
+					    off_t offset, size_t len)
+{
+	const struct eeprom_at2x_config *config = dev->config;
+	const size_t remainder = BIT(config->addr_width) - offset;
+
+	if (len > remainder) {
+		len = remainder;
+	}
+
+	return len;
+}
+
 static int eeprom_at24_read(const struct device *dev, off_t offset, void *buf,
 			    size_t len)
 {
 	const struct eeprom_at2x_config *config = dev->config;
 	struct eeprom_at2x_data *data = dev->data;
 	int64_t timeout;
 	uint8_t addr[2];
+	uint16_t bus_addr;
 	int err;
 
+	bus_addr = eeprom_at24_translate_offset(dev, &offset);
+
 	if (config->addr_width == 16) {
 		sys_put_be16(offset, addr);
 	} else {
 		addr[0] = offset & BIT_MASK(8);
 	}
 
+	len = eeprom_at24_adjust_read_count(dev, offset, len);
+
 	/*
 	 * A write cycle may be in progress so reads must be attempted
 	 * until the current write cycle should be completed.
 	 */
 	timeout = k_uptime_get() + config->timeout;
 	while (1) {
 		int64_t now = k_uptime_get();
-		err = i2c_write_read(data->bus_dev, config->bus_addr,
+		err = i2c_write_read(data->bus_dev, bus_addr,
 				     addr, config->addr_width / 8,
 				     buf, len);
 		if (!err || now > timeout) {
@@ -232,7 +277,11 @@ static int eeprom_at24_read(const struct device *dev, off_t offset, void *buf,
 		k_sleep(K_MSEC(1));
 	}
 
-	return err;
+	if (err < 0) {
+		return err;
+	}
+
+	return len;
 }
 
 static int eeprom_at24_write(const struct device *dev, off_t offset,
@@ -243,9 +292,12 @@ static int eeprom_at24_write(const struct device *dev, off_t offset,
 	int count = eeprom_at2x_limit_write_count(dev, offset, len);
 	uint8_t block[config->addr_width / 8 + count];
 	int64_t timeout;
+	uint16_t bus_addr;
 	int i = 0;
 	int err;
 
+	bus_addr = eeprom_at24_translate_offset(dev, &offset);
+
 	/*
 	 * Not all I2C EEPROMs support repeated start so the the
 	 * address (offset) and data (buf) must be provided in one
@@ -266,7 +318,7 @@ static int eeprom_at24_write(const struct device *dev, off_t offset,
 	while (1) {
 		int64_t now = k_uptime_get();
 		err = i2c_write(data->bus_dev, block, sizeof(block),
-				config->bus_addr);
+				bus_addr);
 		if (!err || now > timeout) {
 			break;
 		}
@@ -404,7 +456,12 @@ static int eeprom_at25_read(const struct device *dev, off_t offset, void *buf,
 		return err;
 	}
 
-	return spi_transceive(data->bus_dev, &data->spi_cfg, &tx, &rx);
+	err = spi_transceive(data->bus_dev, &data->spi_cfg, &tx, &rx);
+	if (err < 0) {
+		return err;
+	}
+
+	return len;
 }
 
 static int eeprom_at25_wren(const struct device *dev)