[flashrom] Giving to -i option some real use

[Michael Karcher]

On 04/19/2016 07:48 PM, Salvador Eduardo Tropea wrote:
> Hi All!
>
> Now I'm using an FPGA board with 4 MiB of flash, was using one with
> 128 kiB. So now the time to read/write/verify the whole memory is
> enough to annoy me ;-)
> So I tried creating a layout like this:
>
> <--
> 00000000:00007e2b fpga
> 00007e2c:003fffff free
> <--
>
> Note: yes only 32300 bytes used, the rest can be used for other
> purposes (0,77%).
>
> And then I used "-i fpga".
> But it didn't help ... flashrom read the 4 MiB twice (one at the
> beggining and another for the verification).
> Looking at the code I found a variable named read_all_first with a
> comment about the lack of implementation.
> So I implemented the needed code to:
> 1) Add a command line option to make it 0 (avoiding the big reads).
> This option can be used only when at least one image is indicated with -i
> 2) Skip the big read when read_all_first is 0. Only the regions
> indicated by the user are actually fetched from the memory.
> 3) Same for the verification stage.
Just a quick question: How does this mix with range erasure? Most
likely, I can't erase 0-7e2b, but I have to erase 0-8000, or even the
whole chip. If the chip was not read before erasing, the contents of
those areas get destroyed. There are use cases for "-i" with the
intention to keep everything in the chip intact except for the selected
address range.
What you need is a way to differentiate between "must not change" and "I
don't care" areas, but the current layout system provides no way to do
that. Traditionally "-i" is interpreted as declaring everything outside
as "must not change", but your description sound like your patch changes
the interpretation to "I don't care".

Regards,
  Michael Karcher