Re: [ECOS] load data from floppy

[davidw at dedasys dot com (David N. Welton)]

Nick Garnett <nickg@ecoscentric.com> writes:

> > I am in the midst of writing an article on eCos, and of course I
> > wanted to create a neat hack to write the article about!

> > To make a long story short, I have a bunch of data that I would
> > like to load up off the raw floppy image.  Probably up until the
> > end of the floppy if possible.

> > Loading the data as a .h file doesn't seem to work as it makes the
> > disk image too big (I get errors when linking).  So I was trying
> > to determine the best way to get the data in memory.  I
> > experimented a bit with making the load not stop at _edata, but
> > I'm not sure exactly where the payload might end up being stashed
> > if I do that.  Maybe another pair of routines instead of endload
> > that keep reading from the disk to a known good location?  Other
> > thoughts?

> The linking problem is probably due to the limited size allowed for
> FLOPPY startup images. Since we use BIOS traps to read the floppy,
> we can only effectively use the bottom 640k of memory. We cannot
> load above the 1M mark without doing a lot of extra messing about.

Exactly what sort of messing about would be needed?  Some sort of
floppy driver?  How does GRUB manage it?:-) A cursory glance at the
code seems to indicate that they have a generic, layered system in
place.  A little bit more complex for those like me who don't grok PC
hardware at the expert level.

> Your best bet might be to use GRUB -- which I added support for some
> time ago. In addition to loading the executable directly to memory
> above the 1M mark, it also allows you to load extra binary files
> anywhere in memory.

> Of course if the purpose of your article is to describe the neat way
> in which you solved this problem then just writing "Err, I used
> GRUB" is probably not going to get it published :-)

No, the article is really just an introduction to eCos.  I was
thinking along the lines of showing how it's smaller than Linux by
squeezing a bunch of stuff (jpegs, in this case) onto a floppy.

It might be nice to be able to do this sort of thing in general, as
the pc-floppy target makes for a good demo platform.

Thankyou,
-- 
David N. Welton
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