RE: [PATCH V3] tiny-printf: Handle formatting of %p with an extra Kconfig

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

From: Tom Rini <trini@konsulko.com>
Sent: Wednesday, May 7, 2025 7:43 PM
> On Wed, Apr 30, 2025 at 12:35:48PM +0200, Christoph Niedermaier wrote:
> 
>> The formatting with %pa / %pap behaves like %x, which results in an
>> incorrect value being output. To improve this, a new fine-tuning
>> Kconfig SPL_USE_TINY_PRINTF_POINTER_SUPPORT for pointer formatting
>> has been added. If it is enabled, the output of %pa / %pap should
>> be correct, and if it is disabled, the pointer formatting is
>> completely unsupported. In addition to indicate unsupported formatting,
>> '?' will be output. This allows enabling pointer formatting only
>> when needed. For SPL_NET and NET_LWIP it is selected by default.
>> Then it also supports the formatting with %pm, %pM and %pI4.
>>
>> In summery this level of %p support for tiny printf is possible now:
>>
>> 1) The standard tiny printf won't have support for pointer formatting.
>>    So it doesn't print misleading values for %pa, instead '?' will be
>>    output:
>>    %p   => ?
>>    %pa  => ?a
>>    %pap => ?ap
>>
>> 2) If SPL_USE_TINY_PRINTF_POINTER_SUPPORT is enabled or DEBUG is defined
>>    tiny printf supports formatting %p and %pa / %pap.
>>
>> 3) If SPL_NET or NET_LWIP is enabled the support of pointers is extended
>>    for %pm, %pM and %pI4.
>>
>> Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
>> ---
>> Cc: Tom Rini <trini@konsulko.com>
>> Cc: Simon Glass <sjg@chromium.org>
>> Cc: Michael Walle <mwalle@kernel.org>
>> Cc: Quentin Schulz <quentin.schulz@cherry.de>
>> Cc: Marek Vasut <marex@denx.de>
>> Cc: Benedikt Spranger <b.spranger@linutronix.de>
>> Cc: Jerome Forissier <jerome.forissier@linaro.org>
>> Cc: John Ogness <john.ogness@linutronix.de>
>> Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
>> ---
>> V2: - Rebase on current master
>>     - Extend commit message
>>     - Restrict use to SPL
>>     - Rename Kconfig to SPL_USE_TINY_PRINTF_POINTER_SUPPORT
>>     - Replace _DEBUG with defined(DEBUG)
>>     - Output '?' if %pm, %pM and %pI4 isn't available
>>     - Add break on case '%'
>> V3: - Add missing output '?' for the default case
>> ---
>>  Kconfig            |  1 +
>>  common/spl/Kconfig |  1 +
>>  lib/Kconfig        |  8 +++++++
>>  lib/tiny-printf.c  | 52 +++++++++++++++++++++++-----------------------
>>  4 files changed, 36 insertions(+), 26 deletions(-)
>>
>> diff --git a/Kconfig b/Kconfig
>> index 51358633762..b8eec3fc931 100644
>> --- a/Kconfig
>> +++ b/Kconfig
>> @@ -774,6 +774,7 @@ config NET
>>
>>  config NET_LWIP
>>  	bool "Use lwIP for networking stack"
>> +	select SPL_USE_TINY_PRINTF_POINTER_SUPPORT if SPL_USE_TINY_PRINTF
>>  	imply NETDEVICES
>>  	help
>>  	  Include networking support based on the lwIP (lightweight IP)
> 
> Sorry I missed this bug until now. This (and the subsequent parts of the
> patch referencing lwIP) aren't right. There's no SPL_NET_LWIP support
> (and not planned at this point), so what this does is grow platforms
> like xilinx_zynq_virt which use lwIP in U-Boot and tiny printf in SPL,
> but shouldn't since there's no SPL_NET_LWIP.

I didn't know that, I took it from the tiny printf pointer handling code.
I will remove all lwIP references in version 4.

Thanks and regards
Christoph