[PATCH v3 4/6] serial: Implement serial_flush() function for console flush() fallback

[Pali Rohár]

On Tuesday 20 September 2022 18:29:02 Tom Rini wrote:
> On Wed, Sep 21, 2022 at 12:18:57AM +0200, Pali Rohár wrote:
> > On Tuesday 20 September 2022 17:40:39 Tom Rini wrote:
> > > On Mon, Sep 05, 2022 at 11:31:19AM +0200, Pali Rohár wrote:
> > > 
> > > > Like in all other console functions, implement also serial_flush() function
> > > > as a fallback int console flush() function.
> > > > 
> > > > Flush support is available only when config option CONSOLE_FLUSH_SUPPORT is
> > > > enabled. So when it is disabled then provides just empty static inline
> > > > function serial_flush().
> > > > 
> > > > Signed-off-by: Pali Rohár <pali at kernel.org>
> > > > Reviewed-by: Simon Glass <sjg at chromium.org>
> > > 
> > > This breaks building on a number of platforms such as ds109 probably due
> > > to DM_SERIAL not being enabled.
> > 
> > ds109 is failing on error:
> > 
> >   LD      u-boot
> > arm-linux-gnueabihf-ld.bfd: common/console.o: in function `flush':
> > /tmp/u-boot/common/console.c:802: undefined reference to `serial_flush'
> > arm-linux-gnueabihf-ld.bfd: common/stdio.o: in function `stdio_serial_flush':
> > /tmp/u-boot/common/stdio.c:93: undefined reference to `serial_flush'
> > make: *** [Makefile:1782: u-boot] Error 1
> > 
> > And serial_flush() is implemented only in serial-uclass.c (which is
> > DM_SERIAL code).
> > 
> > So could you try to add this additional guard (into this 4/6 patch)?
> > 
> > diff --git a/include/serial.h b/include/serial.h
> > index f9009d4046e3..fe01bcfadb9b 100644
> > --- a/include/serial.h
> > +++ b/include/serial.h
> > @@ -362,7 +362,7 @@ void serial_setbrg(void);
> >  void serial_putc(const char ch);
> >  void serial_putc_raw(const char ch);
> >  void serial_puts(const char *str);
> > -#ifdef CONFIG_CONSOLE_FLUSH_SUPPORT
> > +#if defined(CONFIG_CONSOLE_FLUSH_SUPPORT) && CONFIG_IS_ENABLED(DM_SERIAL)
> >  void serial_flush(void);
> >  #else
> >  static inline void serial_flush(void) {}
> > 
> > ds109 with this change compiles fine on my computer.
> 
> It should, but that means that CONSOLE_FLUSH_SUPPORT itself should be
> depending on DM_SERIAL.

No. Because CONSOLE_FLUSH_SUPPORT has nothing with serial. You can have
e.g. LCD/VGA or USB tty output console device on platform without serial
console (where would be whole serial subsystem disabled) and still able
to use new flush support.