[PATCH v3 1/4] debug_uart: Replace debug functions with dummies if CONFIG_DEBUG_UART is not set

[Quentin Schulz]

Hi Łukasz, Kever,

On 11/27/24 11:21 PM, Łukasz Czechowski wrote:
> Hi Kever,
> 
> On 2024/11/27 03:42 Kever Yang <kever.yang at rock-chips.com> wrote:
>>
>> Hi Lukasz,
>>
>>       I got a new error base on patch [1], see full log here [2].
> 
> Looking at the file efi_stub.c that is used in the failing
> configuration it looks to me
> that some functions from debug_uart.h are used here for convenience
> (i.e. printhex),
> even though the DEBUG_UART is not used. This is contrary to my assumption that
> DEBUG_UART_FUNCS macro should not be used if DEBUG UART is not available.
> In order to apply the patch then, either the efi_stub code must be
> updated to not
> use debug functions or the assumption must be relaxed - I'm not yet
> sure what shall be
> the correct approach.
> 

"""
diff --git a/lib/efi/efi_stub.c b/lib/efi/efi_stub.c
index 40fc29d9adf..5172cd78a7c 100644
--- a/lib/efi/efi_stub.c
+++ b/lib/efi/efi_stub.c
@@ -83,12 +83,14 @@ void puts(const char *str)
  		putc(*str++);
  }

+#ifdef CONFIG_DEBUG_UART
  static void _debug_uart_putc(int ch)
  {
  	putc(ch);
  }

  DEBUG_UART_FUNCS
+#endif

  void *memcpy(void *dest, const void *src, size_t size)
  {
"""

Fixes it. It builds fine with and without CONFIG_DEBUG_UART set. Not 
sure if it's proper but I guess that's fine?

While reading the patch again, I think we made a small oversight.

#define printhex8(value) do{}while(0);

is an issue because ch may actually have side effects.

Take for example an interrupt register where reading is acknowledging, 
if one does:

printhex8(readl(INT_REG))

will read the register when CONFIG_DEBUG_UART is set, but not when it's not.

I am not sure if and how we can handle that so that things are executed 
but only print is not called. Is this something we should care about?

Cheers,
Quentin