[U-Boot] [PATCH] tools: mkimage can read input on /dev/stdin

[Wolfgang Denk]

Dear Marek,

In message <201409280001.26383.marex at denx.de> you wrote:
> 
> > Can you please provide values for the size of the binary and the
> > execution time?
> > 
> > It's not really critical, but I'd like to understand the impact of
> > your changes.  You use case is pretty exotic, so it seems a valid
> > question to me to try to understand what the extended functionality
> > costs.
> 
> Won't it be better to focus on the overall concept first and dig in the finer 
> details later ?
> 
> I think right now, the question is -- do we want to support stdin as a source of 
> payload for mkimage or not at all?

The general approach to new features in U-Boot is: 1) is it useful at
least to some? and 2) does it not hurt others?

Re 1), I think the use case is pretty exostic, but apparently there is
at least one user for that.

Re 2), we need some numbers.  Plain mmap() on a regular file is
supposed to be the fastest possible I/O method in a Unix OS, so we
should understand how much a change costs, or if it makes sense to
provide different implementations depending on input type (read() for
stdin vs. mmap() for regular files).  Or if the differences are so
small that this is all not worth the time we spend here.

Best regards,

Wolfgang Denk

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