[PATCH] serial: max310x: fix I2C-only build

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

Allowing the driver to be built when CONFIG_SPI_MASTER is turned off
now causes build failures:

drivers/tty/serial/max310x.c: In function 'max310x_uart_init':
drivers/tty/serial/max310x.c:1737:32: error: 'max310x_spi_driver' undeclared (first use in this function); did you mean 'max310x_i2c_driver'?
 1737 |         spi_unregister_driver(&max310x_spi_driver);
      |                                ^~~~~~~~~~~~~~~~~~
      |                                max310x_i2c_driver
drivers/tty/serial/max310x.c:1737:32: note: each undeclared identifier is reported only once for each function it appears in
drivers/tty/serial/max310x.c:1740:1: error: label 'err_spi_register' defined but not used [-Werror=unused-label]
 1740 | err_spi_register:
      | ^~~~~~~~~~~~~~~~
drivers/tty/serial/max310x.c: At top level:
drivers/tty/serial/max310x.c:1502:29: error: 'regcfg' defined but not used [-Werror=unused-variable]
 1502 | static struct regmap_config regcfg = {
      |                             ^~~~~~

While fixing this, I ran into another problem with I2C=m, which
previously would just not use I2C support.

Fix the #ifdef checks to handle all combinations correctly, and
change the Kconfig dependency to ensure that the driver cannot
be built-in when I2C=m.

Fixes: 20ffe4b3330a ("serial: max310x: allow driver to be built with SPI or I2C")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/tty/serial/Kconfig   |  1 +
 drivers/tty/serial/max310x.c | 40 +++++++++++++++++++-----------------
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 811250bbbd39..b9b40e80ea81 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -323,6 +323,7 @@ config SERIAL_MAX3100
 config SERIAL_MAX310X
 	tristate "MAX310X support"
 	depends on SPI_MASTER || I2C
+	depends on I2C || !I2C
 	select SERIAL_CORE
 	select REGMAP_SPI if SPI_MASTER
 	select REGMAP_I2C if I2C
diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 5168490a1cbb..042ae962c1f6 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1499,6 +1499,20 @@ static const struct of_device_id __maybe_unused max310x_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, max310x_dt_ids);
 
+static const char *max310x_regmap_name(u8 port_id)
+{
+	switch (port_id) {
+	case 0:	return "port0";
+	case 1:	return "port1";
+	case 2:	return "port2";
+	case 3:	return "port3";
+	default:
+		WARN_ON(true);
+		return NULL;
+	}
+}
+
+#ifdef CONFIG_SPI_MASTER
 static struct regmap_config regcfg = {
 	.reg_bits = 8,
 	.val_bits = 8,
@@ -1514,20 +1528,6 @@ static struct regmap_config regcfg = {
 	.max_raw_write = MAX310X_FIFO_SIZE,
 };
 
-static const char *max310x_regmap_name(u8 port_id)
-{
-	switch (port_id) {
-	case 0:	return "port0";
-	case 1:	return "port1";
-	case 2:	return "port2";
-	case 3:	return "port3";
-	default:
-		WARN_ON(true);
-		return NULL;
-	}
-}
-
-#ifdef CONFIG_SPI_MASTER
 static int max310x_spi_extended_reg_enable(struct device *dev, bool enable)
 {
 	struct max310x_port *s = dev_get_drvdata(dev);
@@ -1598,7 +1598,7 @@ static struct spi_driver max310x_spi_driver = {
 };
 #endif
 
-#ifdef CONFIG_I2C
+#if IS_ENABLED(CONFIG_I2C)
 static int max310x_i2c_extended_reg_enable(struct device *dev, bool enable)
 {
 	return 0;
@@ -1724,7 +1724,7 @@ static int __init max310x_uart_init(void)
 		goto err_spi_register;
 #endif
 
-#ifdef CONFIG_I2C
+#if IS_ENABLED(CONFIG_I2C)
 	ret = i2c_add_driver(&max310x_i2c_driver);
 	if (ret)
 		goto err_i2c_register;
@@ -1732,12 +1732,14 @@ static int __init max310x_uart_init(void)
 
 	return 0;
 
-#ifdef CONFIG_I2C
+#if IS_ENABLED(CONFIG_I2C)
 err_i2c_register:
+#endif
+#ifdef CONFIG_SPI_MASTER
 	spi_unregister_driver(&max310x_spi_driver);
+err_spi_register:
 #endif
 
-err_spi_register:
 	uart_unregister_driver(&max310x_uart);
 
 	return ret;
@@ -1746,7 +1748,7 @@ module_init(max310x_uart_init);
 
 static void __exit max310x_uart_exit(void)
 {
-#ifdef CONFIG_I2C
+#if IS_ENABLED(CONFIG_I2C)
 	i2c_del_driver(&max310x_i2c_driver);
 #endif
 
-- 
2.39.5