[U-Boot] [U-Boot, v2] env: don't generate callback list entries for SPL

[Tom Rini <trini@ti.com>]

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On 03/12/2013 01:19 PM, Albert ARIBAUD wrote:
> Hi Scott,
> 
> On Tue, 12 Mar 2013 12:06:53 -0500, Scott Wood 
> <scottwood@freescale.com> wrote:
> 
>> On 03/12/2013 12:02:56 PM, Tom Rini wrote:
>>> On Tue, Mar 12, 2013 at 11:55:22AM -0500, Scott Wood wrote:
>>>> On 03/12/2013 10:30:40 AM, Tom Rini wrote:
>>>>> On Fri, Mar 08, 2013 at 06:35:04PM -0600, Scott Wood 
>>>>> wrote:
>>>>>> Why would eliminating all individual callbacks cause 
>>>>>> start/end
>>> to go
>>>>>> away?  If that's the way the list mechanism works, the 
>>>>>> mechanism needs fixing.
>>>>> 
>>>>> Yes, that's how the mechanism works.  Rather than having to
>>>>> declare that you expect to have a linker list of name $foo,
>>>>> we dynamically determine what linker lists we have and
>>>>> setup the linker section entry.
>>>> 
>>>> So it would break just as hard if we happened to turn off
>>>> all of the things that register callbacks.
>>>> 
>>>>> I'm not sure it's broken exactly, I think maybe we just 
>>>>> need to say no env callback support in SPL since it's not 
>>>>> really user editable.
>>>> 
>>>> That's fine, but it's still a bad mechanism.
>>> 
>>> Yes, the mechanism has a breaking condition on trying to 
>>> reference an empty list (which is what SPL ends up with, in 
>>> this case).  Poking Albert and Marek in case they have any 
>>> ideas, but this seems like a feature not a bug.
>> 
>> How is it a feature?  One of the main benefit of linker lists is 
>> for things to just work when things are configured in/out
>> without needing ifdefs and such.  Why should "everything
>> configured out" be a special case requiring an ifdef?
>> 
>> If we want to save some code by ifdeffing the listwalking code 
>> for SPL, that's a separate matter.
> 
> Normally my reworked linker_list code should work fine with some 
> code going through an empty list, precisely because list start and 
> end symbols, like list entries, are generated by the compiler 
> irrespective of one another and then whatever was generated is 
> sorted by the linker. So an empty list ends up as two symbols at 
> the same address (and indeed, env callbacks, in many boards,
> showed this pattern in the map file).

OK, where's the latest/greatest of this re-work?  I'll see if it also
solves the problem I have.

- -- 
Tom
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