[U-Boot] [PATCH] make hang() a weak function

[Andreas Bießmann]

Dear Wolfgang,

On 04/16/2013 03:05 PM, Wolfgang Denk wrote:
> Dear Andreas,
> 
> In message <516D4B00.9030102 at gmail.com> you wrote:
>>
>>> So it is dead code in mainline, and we will not add it.
>>
>> Well, I don't think it is dead code cause the hang() is called in some ways.
>> This patch opens just the possibility to specialize the hang() by for
>> example a specific board. Maybe this could also be used for specific
>> hang() for different arches when we get closer to the common board files.
> 
> I think it is dead code, and not needed nor useful in mainline.  I
> cannot even see how it would be useful for you.  hang() is defined to
> "hang" the CPU, i. e. to make sure the system will remain in the
> current state.  To me this naturally translates into an infinite loop,
> the implementation of which is completely hardware and architecture
> independent.

Yes it is independent (or should at least). But there are still slightly
different versions:

---8<---
arch/blackfin/lib/board.c:void hang(void)
arch/blackfin/lib/board.c-{
arch/blackfin/lib/board.c-#ifdef CONFIG_STATUS_LED
arch/blackfin/lib/board.c-      status_led_set(STATUS_LED_BOOT,
STATUS_LED_OFF);
arch/blackfin/lib/board.c-      status_led_set(STATUS_LED_CRASH,
STATUS_LED_BLINKING);
--->8---

---8<---
arch/arm/lib/board.c:void __hang(void)
arch/arm/lib/board.c-{
arch/arm/lib/board.c-   puts("### ERROR ### Please RESET the board ###\n");
arch/arm/lib/board.c-   for (;;);
arch/arm/lib/board.c-}
--->8---

---8<---
arch/powerpc/lib/board.c:void __hang(void)
arch/powerpc/lib/board.c-{
arch/powerpc/lib/board.c-       puts("### ERROR ### Please RESET the
board ###\n");
arch/powerpc/lib/board.c-       bootstage_error(BOOTSTAGE_ID_NEED_RESET);
arch/powerpc/lib/board.c-       for (;;)
--->8---

> Note that hang() is not supposed to do anything else, it just hangs
> the system.  If you have a debugger attached, you will be able to do a
> simple stack backtrace and see exactly where you are hanging, and why.

Well, for this specific board I plan to panic() on wrong hardware
detection (which will in turn call hang()). My requirements say that I
have to visualize this state then, I thought it would be a good idea to
blink some lights in the endless loop in hang() for this specific board.

> If you think you need to have specialized code, you are doing
> something wrong.

Really? How would you solve this requirement?

Best regards

Andreas Bießmann