tests: drivers: i2c: i2c_target_api: configure transfer byte size

Add CONFIG_I2C_TEST_DATA_MAX_SIZE to I2C driver i2c_target_api tests
to set the max data size of tested I2C transfer. The effective I2C
transfer  data size depends on that value and the size of the
EEPROM defined in the board DTS file.

Signed-off-by: Etienne Carriere <[email protected]>

Author: etienne-lms

tests/drivers/i2c/i2c_target_api/README.txt

@@ -39,3 +39,9 @@ Presence of this required hardware configuration is identified by the
 `i2c_bus_short` fixture.  If the buses are not connected as required,
 or the controller driver has bugs, the test will fail one or more I2C
 transactions.
+
+Transfer data size
+******************
+
+One can tune the number of data bytes echanged during the tests using
+configuration option ``CONFIG_I2C_TEST_DATA_MAX_SIZE``.

tests/drivers/i2c/i2c_target_api/common/Kconfig

@@ -17,3 +17,7 @@ config I2C_VIRTUAL_NAME
 
 config APP_DUAL_ROLE_I2C
 	bool "Test with combined controller/target behavior"
+
+config I2C_TEST_DATA_MAX_SIZE
+	int "Max tested data size for the I2C transfers"
+	default 20

tests/drivers/i2c/i2c_target_api/src/main.c

@@ -23,9 +23,11 @@
 #define NODE_EP0 DT_NODELABEL(eeprom0)
 #define NODE_EP1 DT_NODELABEL(eeprom1)
 
-#define TEST_DATA_SIZE	20
-static const uint8_t eeprom_0_data[TEST_DATA_SIZE] = "0123456789abcdefghij";
-static const uint8_t eeprom_1_data[TEST_DATA_SIZE] = "jihgfedcba9876543210";
+#define TEST_DATA_SIZE	MIN(CONFIG_I2C_TEST_DATA_MAX_SIZE, \
+			    MIN(DT_PROP(NODE_EP0, size), DT_PROP(NODE_EP1, size)))
+
+static uint8_t eeprom_0_data[TEST_DATA_SIZE];
+static uint8_t eeprom_1_data[TEST_DATA_SIZE];
 static uint8_t i2c_buffer[TEST_DATA_SIZE];
 
 /*
@@ -35,6 +37,23 @@ static uint8_t i2c_buffer[TEST_DATA_SIZE];
 uint8_t buffer_print_eeprom[TEST_DATA_SIZE * 5 + 1];
 uint8_t buffer_print_i2c[TEST_DATA_SIZE * 5 + 1];
 
+static void init_eeprom_test_data(void)
+{
+	size_t n;
+
+	/*
+	 * Initialize EEPROM data with printable ASCII value (range [32 126]).
+	 * Make sure content differs between eeprom_0_data[] and eeprom_1_data[].
+	 */
+	for (n = 0; n < sizeof(eeprom_0_data); n++) {
+		eeprom_0_data[n] = 32 + (n % (126 - 32));
+	}
+
+	for (n = 0; n < sizeof(eeprom_1_data); n++) {
+		eeprom_1_data[n] = 32 + (((n + 10) * 3) % (126 - 32));
+	}
+}
+
 static void to_display_format(const uint8_t *src, size_t size, char *dst)
 {
 	size_t i;
@@ -123,7 +142,7 @@ static int run_program_read(const struct device *i2c, uint8_t addr,
 		i2c->name, addr, offset);
 
 	for (i = 0 ; i < TEST_DATA_SIZE-offset ; ++i) {
-		i2c_buffer[i] = i;
+		i2c_buffer[i] = i & 0xFF;
 	}
 
 	switch (addr_width) {
@@ -155,11 +174,11 @@ static int run_program_read(const struct device *i2c, uint8_t addr,
 	zassert_equal(ret, 0, "Failed to read EEPROM");
 
 	for (i = 0 ; i < TEST_DATA_SIZE-offset ; ++i) {
-		if (i2c_buffer[i] != i) {
+		if (i2c_buffer[i] != (i & 0xFF)) {
 			to_display_format(i2c_buffer, TEST_DATA_SIZE-offset,
 					  buffer_print_i2c);
-			TC_PRINT("Error: Unexpected buffer content: %s\n",
-				 buffer_print_i2c);
+			TC_PRINT("Error: Unexpected %u (%02x) buffer content: %s\n",
+				 i, i2c_buffer[i], buffer_print_i2c);
 			return -EIO;
 		}
 	}
@@ -235,6 +254,8 @@ ZTEST(i2c_eeprom_target, test_eeprom_target)
 	uint8_t addr_1_width = DT_PROP_OR(NODE_EP1, address_width, 8);
 	int ret, offset;
 
+	init_eeprom_test_data();
+
 	zassert_not_null(i2c_0, "EEPROM 0 - I2C bus not found");
 	zassert_not_null(eeprom_0, "EEPROM 0 device not found");