[flashrom] Add option to disable the reading back of the flash contents at write operation

[Márton Miklós]

Hello David,

Thank you for your response!

Your answer makes sense for me. In this case it would be useful to 
refactor the "backupless" writes to read sectors only until a non 0xFF 
portion found, and then mark that sector erasable or erase immediately. 
In the case if the flash has non blank region this could speed up the 
programming, worst case (programming a fully erased chip) it is going to 
be equal in time.

I have not been aware of Nico's patch. Is it already merged to the 
mainline? If not could you please give me a link to that?
Thank you!

Regards,
Miklos Marton

2015-12-11 21:52 keltezéssel, David Hendricks írta:
> Hi Marton,
> I respectfully disagree with this approach. Reading the old contents 
> is not just used for backup. It's used so that flashrom can 
> selectively erase and write blocks which usually saves time because 
> erase and write operations are orders of magnitude slower than reads 
> on NOR flash.
>
> So, it's not a bad thing to support this option, but I think there is 
> little benefit and can actually make the process slower in most cases. 
> (Your case might be different, of course)
>
> Nico Huber's unbounded read patch should help reduce the initial read 
> time by a large factor (~90% reduction). Try marking your chip as 
> tested for unbounded reads. You might find that the read and selective 
> erase/write is faster than unconditional erase/write.
>
>
> On Fri, Dec 11, 2015 at 12:01 PM, Márton Miklós 
> <martonmiklosqdev at gmail.com <mailto:martonmiklosqdev at gmail.com>> wrote:
>
>     Hello all,
>
>     I am using the flashrom with an external programmer to flash
>     various SPI flashes a lot.
>     In most cases I do not care about the old flash contents when
>     flashing, so the "/Reading old flash chip contents/" step does not
>     have any added value in my use cases. The code also has a FIXME
>     note where this is hardcoded to make it configurable in the
>     future. I would like to patch it if possible.
>
>     Please propose me command line arguments for disabling it. My
>     proposal:
>     /-N | --nobackup  skip reading back old flash contents before write/
>
>     I know -N could be confused with -n but the same applies to the -v
>     (verify) and -V (verbose).
>     I also could live without the short argument, but that would break
>     the "standard".
>
>     Thanks in advance for your feedback!
>
>     -- 
>     Regards,
>     Miklos Marton
>
>
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>
>
>
>
> -- 
> David Hendricks (dhendrix)
> Systems Software Engineer, Google Inc.

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