[U-Boot] Inconsistencies in commands regarding load_addr

[Benoît Thébaudeau]

Dear Wolfgang,

On 08/10/2015 23:29, Wolfgang Denk wrote:
> Dear Stephen,
> 
> In message <56167DB6.3000508 at wwwdotorg.org> you wrote:
>>
>>>> What's the expected correct behavior here?
>>>
>>> After successful loading the data to memory, load_addr should be set
>>> correctly, for all commands.  In the error case, the value of
>>> load_addr is undefined.
>>
>> Is this documented anywhere? If not, I'm not convinced that there's a 
>> contract to be followed; it "just happens" that some filesystem-related 
>> commands work(ed) that way (and as Benoît pointed out, apparently some 
>> don't irrespective of the mentioned patch).
> 
> I'm afraid it's not documented, but it is what I would consider a sane
> and consistent behaviour.  If we intend to implement POLA [1] (and I
> very much think we should), this is how U-Boot should behave.
> 
> 
> [1] https://en.wikipedia.org/wiki/Principle_of_least_astonishment

I'm not certain that this would be the least astonishing behavior. When I read
the documentation, I rather expect the loadaddr environment variable to be used
whenever the address is omitted in a command invocation. Moreover, one may have
to read/load several data pieces before booting, and the last loaded piece would
not necessarily be the one containing the kernel to be booted. This should at
least be documented.

Another approach would be to compel users to pass an address for all commands.
Implicit behaviors are always dangerous, all the more if they are undocumented.
But of course, this would break some existing configurations.

Best regards,
Benoît