Re: [PATCH] earlycon: Fix compile error when SERIAL_CORE is m

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Oct 20, 2022 at 09:20:24PM +0800, zhangxiaoxu (A) wrote:
> 
> 
> On 2022/10/20 13:04, Greg KH wrote:
> > On Thu, Oct 20, 2022 at 11:27:22AM +0800, Zhang Xiaoxu wrote:
> > > When set CONFIG_SERIAL_EARLYCON=y and CONFIG_SERIAL_CORE=m, there is
> > > a compile error as below:
> > > 
> > >    ld: vmlinux.o: in function `parse_options.constprop.0':
> > >    earlycon.c:(.init.text+0xba5a3): undefined reference to `uart_parse_earlycon'
> > > 
> > > Since the SERIAL_EARLYCON use 'uart_parse_earlycon' which defined in
> > > SERIAL_CORE, so should select rather than depends on.
> > 
> > No, please try to never use "select".
> > 
> > > 
> > > Fixes: 9aac5887595b ("tty/serial: add generic serial earlycon")
> > 
> > So this has been a problem for a very very long time and never been
> > seen until now?  That feels wrong, what changed to cause this to not
> > ever be hit before with all of the tens of thousands of random configs
> > that have been built since this very old kernel?
> > 
> Yes, 0fb9342d06b0 ("tty: serial: earlycon dependency") already fix the
> same issue with add "depends on SERIAL_CORE".
> 
> But there are some other scenarios can trigger the same issue.
> 
> Use the config file in the bugzilla can reproduce the problem.
> https://bugzilla.kernel.org/show_bug.cgi?id=216611
> 
> Bisect with this config, find out the following commit introduce the issue:
>   cdcc41a256efe8 ("tty: serial: Kconfig: Allow SERIAL_QCOM_GENI_CONSOLE to be enabled if SERIAL_QCOM_GENI is a module")
> 
>  config SERIAL_QCOM_GENI
>         tristate "QCOM on-chip GENI based serial port support"
>         depends on ARCH_QCOM || COMPILE_TEST
>         depends on QCOM_GENI_SE
>         select SERIAL_CORE
> 
>  config SERIAL_QCOM_GENI_CONSOLE
>         bool "QCOM GENI Serial Console support"
> -       depends on SERIAL_QCOM_GENI=y
> +       depends on SERIAL_QCOM_GENI
>         select SERIAL_CORE_CONSOLE
>         select SERIAL_EARLYCON
>         help
>           Serial console driver for Qualcomm Technologies Inc's GENI based
>           QUP hardware.

Then this is an issue with that driver Kconfig options, not with the tty
core options.  Please fix it up there.

thanks,

greg k-h