linux-kernel - Re: how to look for source code in kernel

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Date:	Fri, 28 Dec 2012 14:07:34 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	anish singh <anish198519851985@...il.com>,
	amit mehta <gmate.amit@...il.com>,
	Henrique Rodrigues <henriquesilvar@...il.com>,
	kishore kumar <kishoreopen@...il.com>,
	Jonathan Neuschäfer <j.neuschaefer@....net>,
	linux-kernel@...r.kernel.org, Kernelnewbies@...nelnewbies.org
Subject: Re: how to look for source code in kernel

On Thu, Dec 27, 2012 at 11:36:13PM -0800, Eric W. Biederman wrote:
> git-ls-files | xargs fgrep 'struct f2fs_inode'
> 
> That returns instantly and tells me where to look.  If you can do an
> instant brute force search what is the point of an index?

Not if you're using a lame-ass laptop with a rotating disk:

$ time git ls-files | xargs grep -E 'struct mce\W*{'
arch/x86/include/uapi/asm/mce.h:struct mce {
arch/x86/kernel/cpu/mcheck/mce.c:               if (!final || memcmp(m, final, sizeof(struct mce))) {

real    2m48.415s
user    0m2.388s
sys     0m15.668s

What I've grown accustomed to is cscope with a prior find run on the
kernel source tree to create a custom cscope.files which cscope uses to
index and then using vim bindings in cscope so that if, for example, the
cursor is on a function call, executing a keyboard shortcut opens the
definition of that function in another vim tab. I.e., a thin IDE done
right.

> My experience with gui editors is that they always hide something I
> need to see, or my code is just strange enough (say having asm file,
> or supporting multiple architectures) that the tools get horribly
> confused.

That's true, then I tend to use another xterm with tabbed vim showing
additional files. Btw, git ls-files assumes a source file is tracked by
git and in the seldom case where you're adding new, yet untracked files,
that won't work.

So probably a mixed approach of cscope in one window and grep + editor
in another would cover all bases. For a newbie who wants to only browse
the code, cscope should be enough for starters, I'd say.

Thanks.

-- 
Regards/Gruss,
Boris.
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