[[PATCH 1/2] serial: 8250: fix building mediatek with SERIAL_8250=m] On 08/02/2016 (Mon 13:51) Arnd Bergmann wrote:

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':
8250_ingenic.c:(.text+0x1bee8): undefined reference to `serial8250_do_set_termios'
8250_ingenic.c:(.text+0x1bf10): undefined reference to `uart_get_baud_rate'
8250_ingenic.c:(.text+0x1c09c): undefined reference to `uart_get_divisor'
drivers/tty/built-in.o: In function `mtk8250_do_pm':
8250_ingenic.c:(.text+0x1c0d0): undefined reference to `serial8250_do_pm'
drivers/tty/built-in.o: In function `mtk8250_probe':
8250_ingenic.c:(.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]

Probably should drop the ingenic lines above ; assuming they are make -j N
related and that mtk doesn't depend on or build ingenic.

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>.

Note that the driver uses builtin_platform_driver() and implements
no .remove() callback, so unloading the module is not possible.

But this is due to d72d391c126e0ffd3047c06c4bef4d795853d5d5.  So again,
I'm not sure what this achives vs. just making it depend on having
SERIAL_8250=y as a trivial fix for the one build issue.

If you really see a use case for tristate, then the above should be
reverted before adding your conversion to tristate I think.

Paul.
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