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Re: [PATCH 1/2] serial: 8250: fix building mediatek with SERIAL_8250=m

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  Re: [PATCH 1/2] serial: 8250: fix building mediatek with  SERIAL_8250=m Matthias Brugger <matthias.bgg@gmail.com> - 2016-02-10 19:10 +0100
    Re: [PATCH 1/2] serial: 8250: fix building mediatek with SERIAL_8250=m Arnd Bergmann <arnd@arndb.de> - 2016-02-10 21:00 +0100

#1331408 — Re: [PATCH 1/2] serial: 8250: fix building mediatek with SERIAL_8250=m

On 08/02/16 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]
>
> 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.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---

I tried this with:
commit 2178cbc68f3602dc0b5949b9be2c8383ad3d93ef

$ grep 8250 .config
CONFIG_SERIAL_8250=m
# CONFIG_SERIAL_8250_DEPRECATED_OPTIONS is not set
CONFIG_SERIAL_8250_PCI=m
CONFIG_SERIAL_8250_NR_UARTS=4
CONFIG_SERIAL_8250_RUNTIME_UARTS=4
# CONFIG_SERIAL_8250_EXTENDED is not set
# CONFIG_SERIAL_8250_DW is not set
# CONFIG_SERIAL_8250_RT288X is not set
CONFIG_SERIAL_8250_MT6577=y
# CONFIG_SERIAL_8250_INGENIC is not set
# CONFIG_SERIAL_8250_MID is not set

$ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- drivers/tty/

compiles just fine.

Do I missing something?

Regards,
Matthias

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#1331462 — Re: [PATCH 1/2] serial: 8250: fix building mediatek with SERIAL_8250=m

On Wednesday 10 February 2016 19:06:27 Matthias Brugger wrote:
> > ---
> 
> I tried this with:
> commit 2178cbc68f3602dc0b5949b9be2c8383ad3d93ef
> 
> $ grep 8250 .config
> CONFIG_SERIAL_8250=m
> # CONFIG_SERIAL_8250_DEPRECATED_OPTIONS is not set
> CONFIG_SERIAL_8250_PCI=m
> CONFIG_SERIAL_8250_NR_UARTS=4
> CONFIG_SERIAL_8250_RUNTIME_UARTS=4
> # CONFIG_SERIAL_8250_EXTENDED is not set
> # CONFIG_SERIAL_8250_DW is not set
> # CONFIG_SERIAL_8250_RT288X is not set
> CONFIG_SERIAL_8250_MT6577=y
> # CONFIG_SERIAL_8250_INGENIC is not set
> # CONFIG_SERIAL_8250_MID is not set
> 
> $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- drivers/tty/
> 
> compiles just fine.
> 
> Do I missing something?
> 

I was simplifying the situation in the patch description: When CONFIG_SERIAL_8250=m,
Kbuild does not actually descend into drivers/tty/serial/8250/ while building
built-in code, so none of the built-in subdrivers actually get built.

After spotting the problem, I was building with this patch that I considered
submitting:

diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index ceba33c4ebb4..28121885e78e 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -18,7 +18,7 @@ obj-$(CONFIG_SERIAL_SUNSU) += sunsu.o
 obj-$(CONFIG_SERIAL_SUNSAB) += sunsab.o
 
 # Now bring in any enabled 8250/16450/16550 type drivers.
-obj-$(CONFIG_SERIAL_8250) += 8250/
+obj-y += 8250/
 
 obj-$(CONFIG_SERIAL_AMBA_PL010) += amba-pl010.o
 obj-$(CONFIG_SERIAL_AMBA_PL011) += amba-pl011.o

However, after the other problems are fixed, it's not actually needed
any more, so I did not submit it.

	Arnd

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