[Buildroot] Placement of custom module-building in buildrootprocedure

[Sean Parker <supinlick@yahoo.com>]

Ulf - 

  Thanks so much for your reply.

  It's difficult moving from the application-development
world
to the embedded world where kernel issues become prevalant
- 
please bear with my ignorance...

> You should develop your linux driver separate from
>  buildroot, and then generate a patch.

I've started by moving my code to the linux tree, say
under:
 
$(KDIR)/drivers/mymod
   |
   + mymod.c
   |
   + Makefile <-  includes obj-m+=mymod.o

Of course then I do have to edit $(KDIR)/drivers/Makefile 
to include "mymod/" as a subdir

> By using the advanced linux configuration you can supply
> a path to the patch, and when linux is decompressed,
> your patch will be applied to the linux source tree.

How do I make a patch to the linux kernel? (I thought the
patch
process needed some reference tree in order to know "what's
different")

However, I do see how a patch is the best solution to 
leaving the distro-linux package untouched. At what point
in the
buildroot process/structure do I indicate I have a patch?
I do have other application code I'm including in my
project
as a separate package to the buildroot structure - can I
put the 
patch reference in my <my_proj>.mk file? (the one placed
under
buildroot/packages/<my_proj>)

> By giving the command:
>
>$ make configured
>
> you will stop the build before anything is compiled.
> Go into the linux source directory in
$(PROJECT_BUILD_DIR)
> and do 
>
> $ make ARCH=mips xconfig.
>
>Save the configuration and ensure that the .config is
> available somewhere in the buildroot tree and that 
> LINUX26_KCONFIG is the path to the file.

I'm just leaving $(KDIR)/.config alone for now - if I make 
mymod "always" I shouldn't need to mees with this should I?

Otherwise, I'm saving the various buildroot/busybox config
files
off in my own location, and overwriting the vendor versions
when I do a clean build, that way I preserve my own copies
while
being able to reinstall the vender version cleanly also
(without the
extra make menuconfig step every time). 

> One way of doing this automatically is to do
>   make saveconfig
>
> This will store your configuration files under
"local/<project>".
>

How does it know, unless I tell it to save it somewhere
else? It sounds like
you're saying it'll know about my project just by doing the

make xconfig, but I don't understand how it gets in there
without
me editing a config file otherwise...

<snip my stuff>

> Best Regards
> Ulf Samuelsson

I guess the main confusion here [with me] is the
distinction between 
"kernel-" vs. "external-" modules, and the orthogonal ideas
of
"cross-compiling" and "adding modules to a local running
kernel."

  for example:

            X-compile             pre-built
                                   kernel
         -----------------------------------------
         |                     |
 kernel  |  use obj-y          | compile a module
  mod    |  in kbuild file     | and re-make linux 
         |  within buildroot   | kernel
         |  context            |
         |                     |
         -----------------------------------------
         |                     |
 external|  as buildroot pkg   |
  mod    |  refer to code      |
         |  outside of context | compile a module and
         |  of linux tree ??? -| do insmod straight-away
         |  or do a patch to   | to load it for this 
         |  hack it in         | session only
         |                     |
         -----------------------------------------

Does this make sense? Please correct my understanding...

The documentation I suppose takes for granted that these
are clearly
defined contexts in anyone's discussion of the issues - and
thus the need
for newbies to constantly ask the same questions - i.e.
"how do I add a module?"

Thanks for your time and effort
   Sean Parker





God Bless 
    Sean Parker 





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