[U-Boot] [PATCH 62/71] serial: spl: Implement empty functions for SPL

Scott Wood
2012-09-18T18:25:34Z

On 09/18/2012 01:03:17 PM, Marek Vasut wrote:
> Dear Scott Wood,
>
> > On 09/18/2012 12:13:57 PM, Marek Vasut wrote:
> > > Dear Tom Rini,
> > >
> > > > On Mon, Sep 17, 2012 at 01:21:27AM +0200, Marek Vasut wrote:
> > > > > Implement empty serial_* functions for SPL without serial
> > > > > support enabled. This is imperative to haave once serial
> > > > > multi is enabled unconditionally.
> > > > >
> > > > > Signed-off-by: Marek Vasut <marex@denx.de>
> > > > > Cc: Marek Vasut <marek.vasut@gmail.com>
> > > > > Cc: Tom Rini <trini@ti.com>
> > > > > ---
> > > > >
> > > > > common/serial.c | 12 ++++++++++++
> > > > > 1 file changed, 12 insertions(+)
> > > > >
> > > > > diff --git a/common/serial.c b/common/serial.c
> > > > > index 631af65..cef4ba8 100644
> > > > > --- a/common/serial.c
> > > > > +++ b/common/serial.c
> > > > > @@ -27,6 +27,16 @@
> > > > >
> > > > > #include <post.h>
> > > > > #include <linux/compiler.h>
> > > > >
> > > > > +/* Implement prototypes for SPL without serial support */
> > > > > +#if defined(CONFIG_SPL_BUILD) &&
> > >
> > > !defined(CONFIG_SPL_SERIAL_SUPPORT)
> > >
> > > > > +int serial_init(void) { return 0; }
> > > > > +void serial_setbrg(void) {}
> > > > > +int serial_getc(void) { return 0; }
> > > > > +int serial_tstc(void) { return 0; }
> > > > > +void serial_putc(const char c) {}
> > > > > +void serial_puts(const char *s) {}
> > > >
> > > > This isn't quite right. We need to allow for:
> > > > - No output SPL, strings collected (so #defined to do{} while
> (0))
> > >
> > > Which is not type-checked and will drag in bugs.
> >
> > Not all that likely, since most code will either be built with
> printf
> > enabled some of the time, or not contain printf (i.e. it's not quite
> > the same situation as debug prints which may be rarely enabled).
> >
> > An inline function would be fine, but has to be done at the same
> place
> > that normal printf is declared -- whereas a macro could be done
> after
> > the fact. Unless you use a macro to redirect it to an inline
> function
> > of a different name...
> >
> > I do not understand why you want to put these stubs in a C file
> instead
> > of a header file, though -- you're preventing code from being
> optimized
> > away, which is important in some SPLs.
>
> I'd say the GCC must optimize it out anyway.

I think I got some wires crossed and was thinking about printf/puts.
We want those to be optimized away at compile time (not pointed to a
stub at link time) on an SPL that has no output support, but once
that's done the low level serial functions shouldn't be referenced
anymore, right?

-Scott