[PATCH v3 5/5] serial: 8250/mediatek: fix building with SERIAL_8250=m

[Arnd Bergmann]

The Mediatek 8250 driver has a 'bool' Kconfig symbol, but that
breaks when SERIAL_8250 is a loadable module:

drivers/tty/built-in.o: In function `mtk8250_set_termios':
:(.text+0x1bee8): undefined reference to `serial8250_do_set_termios'
:(.text+0x1bf10): undefined reference to `uart_get_baud_rate'
:(.text+0x1c09c): undefined reference to `uart_get_divisor'
drivers/tty/built-in.o: In function `mtk8250_do_pm':
:(.text+0x1c0d0): undefined reference to `serial8250_do_pm'
drivers/tty/built-in.o: In function `mtk8250_probe':
:(.text+0x1c2e4): undefined reference to `serial8250_register_8250_port'
serial/8250/8250_mtk.c:287:242: error: data definition has no type or storage class [-Werror]
serial/8250/8250_mtk.c:287:122: error: 'mtk8250_platform_driver_init' defined but not used [-Werror=unused-function]

This changes the symbol to a 'tristate', so the dependency on
SERIAL_8250 also works when that is set to 'm'.
To actually build the driver, we also need to include <linux/module.h>.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Matthias Brugger <matthias.bgg@xxxxxxxxx>
---
 drivers/tty/serial/8250/8250_mtk.c | 2 +-
 drivers/tty/serial/8250/Kconfig    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index 6ecc6e3e82dc..a0294f3de4f8 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -303,7 +303,7 @@ static struct platform_driver mtk8250_platform_driver = {
 };
 module_platform_driver(mtk8250_platform_driver);
 
-#ifdef CONFIG_SERIAL_8250_CONSOLE
+#if defined(CONFIG_SERIAL_8250_CONSOLE) && !defined(MODULE)
 static int __init early_mtk8250_setup(struct earlycon_device *device,
 					const char *options)
 {
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 1b0638511ac1..c45a02a7f9e2 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -370,7 +370,7 @@ config SERIAL_8250_LPC18XX
 	  serial port, say Y to this option. If unsure, say Y.
 
 config SERIAL_8250_MT6577
-	bool "Mediatek serial port support"
+	tristate "Mediatek serial port support"
 	depends on SERIAL_8250 && ARCH_MEDIATEK
 	help
 	  If you have a Mediatek based board and want to use the
-- 
2.7.0