RE: [PATCH] tiny-printf: Add support for upper case hex values

[Christoph Niedermaier <cniedermaier@dh-electronics.com>]

From: Michael Walle <mwalle@kernel.org>
Sent: Monday, April 7, 2025 7:28 AM
> Hi,
> > > > > I wouldn't mind printing the pointer for %p[mMI], but %pa prints the
> > > > > *content* of the pointer which is really confusing. I.e. in
> > > > > pinctrl-single.c the reg value pairs are printed like
> > > > >
> > > > >   dev_dbg(dev, "reg/val %pa/0x%08x\n", &reg, val);
> > > > >
> > > > > with reg being a pointer to a physical address. So with tiny_printf
> > > > > the address of reg (which is a pointer to the stack) is printed in
> > > > > this case.
> > > > >
> > > > > I don't think we can print %p without putting more logic into the
> > > > > decoding. I think the culprit here is the fallthrough to %x, which
> > > > > then leads to the confusing behavior shown above. IMHO if we want to
> > > > > avoid that, we'd have to make %p entirely unsupported.
> > > > >
> > > > > diff --git a/lib/tiny-printf.c b/lib/tiny-printf.c
> > > > > index faf55d7f327..8147ffa2c1b 100644
> > > > > --- a/lib/tiny-printf.c
> > > > > +++ b/lib/tiny-printf.c
> > > > > @@ -269,21 +269,18 @@ static int _vprintf(struct printf_info *info, const char *fmt, va_list va)
> > > > >  						div_out(info, &num, div);
> > > > >  				}
> > > > >  				break;
> > > > > +#if CONFIG_IS_ENABLED(NET) || CONFIG_IS_ENABLED(NET_LWIP) || _DEBUG
> > > >
> > > > What if we fine-tune tinyprinf via config here?
> > > > For example SPL_USE_TINY_PRINTF_POINTER_SUPPORT and
> > > > select it by NET or NET_LWIP. If someone needs it,
> > > > the pointer output can be enabled, otherwise '?' for
> > > > unsupported is output.
> > >
> > > Yeah I had a similar idea, but I'm not sure if yet another config
> > > symbol is worth it. That's up to the maintainer to decide :)
> > >
> > > In any case, we have a different behavior to what is printed
> > > right now, as we drop the fallthrough to %x. Tom? Simon?
> >
> > A Kconfig symbol that NET||NET_LWIP select seems fine, and fall through
> > to printing "?".
> 
> Great! Christoph, will you prepare a patch or should I?

OK, I will prepare a patch.

Regards
Christoph