[U-Boot] [PATCH 1/5] Add bmp_layout module for accessing BMP header data

[Nikita Kiryanov <nikita@compulab.co.il>]

Dear Wolfgang Denk,

On 02/04/2013 09:26 PM, Wolfgang Denk wrote:
> Dear Nikita Kiryanov,
>
> In message <1359977979-28585-2-git-send-email-nikita@compulab.co.il> you wrote:
>> Currently code that displays BMP files does two things:
>> * assume that any address is a valid load address for a BMP
>> * access in-memory BMP header fields directly
>>
>> Since some BMP header fields are 32 bit wide, this has a potential
>> for causing data aborts when these fields are placed in unaligned
>> addresses.
>>
>> Create an API for safely accessing BMP header data, and compile it with
>> $(PLATFORM_NO_UNALIGNED) to give it the ability to emulate unaligned memory
>> accesses.
>
> Frankly,  I think this is overkill.  U-Boot is a bootloader, and it is
> supposed to be lean and eficient.  We don't have all levels of safety
> systems and protective devices as in, for example, an aircraft.  You
> are supposed to know what you are doing, and if you ignore the rules,
> you will quickly see the results yourself.

[...]

> You talk about BMP header - but we also have alignment requirements
> for image headers, well, even for a plain "md" or "mw" command.  And
> none of these provide any protection against accidsential (or
> intentional) access to unaligned addresses.

That's true, but when md traps you simply restart the board and
everything's fine. If displaying a splash screen traps- you're stuck.
I'm not saying we should start implementing protection against every
possible mistake, but when the repercussions are this serious I feel
that protection is in order.

There's a difference between a bicycle with no training wheels and one
that falls apart when you turn it the wrong way.

>
> My recommendation is: just don;t do it, then.
>
> Best regards,
>
> Wolfgang Denk
>


-- 
Regards,
Nikita.