Re: [PATCH] tty: 8250_dw: fix build error for CONFIG_SERIAL_8250=m

[Arnd Bergmann <arnd@arndb.de>]

On Wednesday 24 August 2011, Jamie Iles wrote:
> Allow 8250_dw to be built as a module and export serial8250_handle_irq
> so that 8250 can still be built as a module.  This prevents the
> following build failure:
> 
> drivers/built-in.o: In function `dw8250_handle_irq':
> 8250_dw.c:(.text+0xcad9c): undefined reference to `serial8250_handle_irq'

I think this won't fix the bug that Stephen was reporting, it will only
make the error message go away but it won't work in the end: When
CONFIG_SERIAL_8250_DW is set to 'm', the declaration of
serial8250_use_designware_io now gets stubbed out from of_serial.ko,
meaning that the 8250_dw module becomes useless.

At the very least you also need to export the serial8250_use_designware_io
symbol and check for CONFIG_SERIAL_8250_DW_MODULE in the header.

When go go to such length, I think the approach I initially advocated
(making 8250_dw a standalone platform_driver like of_serial) will be
nicer.

Another alternative would be to link 8250_dw.o into 8250.ko, but that
requires renaming the module and will conflict with some of the other
changes I'm still planning to do with the 8250 driver.

	Arnd