Is there a tool which can generate a small and simple source tree after config?

[Javier Martinez Canillas]

On Sun, Oct 23, 2011 at 6:29 PM, jiangtao.jit <jiangtao.jit at gmail.com> wrote:
> Hi:
>

Hi jiangtao,

> While reading the kernel code
> 1. the huge amount of files make me scared
>    there are too many alike functions in different files
>    sometimes I can't figure out which one was really compiled
> 2. too many macros in the definition of a struct or functions declaration
>    confused me a lot
>    I tried to follow the generated file autoconf.h to guess the final face
>    but it's really a difficult thing
>
> Is there a tool which can generate a small and simple source tree after config?
> not pre-processor

Not that I'm aware of.

> just generate a small source tree contains the files and dirs which really will be compiled
> and no macros like CONFIG_SMP etc.
> according to the configuration
>
> or some other way to understand the architecture of the final working source tree?
>

The Linux kernel is a very complex beast yet it is highly modularized.
I recommend you to focus on the specific subsystem that you need to
work and don't worry about the rest.

To know if a specific file is included in your kernel I usually do
this (it works for me but I'm not sure if is the right way to do it):

For example if I want to know if the driver to support nand memories
on ARM OMAP platforms is included in my kernel.

1- Find the file that implements the driver (drivers/mtd/nand/omap2.c)

2- See which Kconfig symbol determines its compilation:

$ fgrep omap2 drivers/mtd/nand/Makefile
obj-$(CONFIG_MTD_NAND_OMAP2) 		+= omap2.o

3- Look if that symbol is included in my config file:

$ fgrep MTD_NAND_OMAP2 .config
CONFIG_MTD_NAND_OMAP2=y

Then I know that my kernels includes that file.


Hope it helps,

-- 
Javier Martínez Canillas
(+34) 682 39 81 69
Barcelona, Spain