[yocto] Where does the bitbake get the variable "TOPDIR"

[Bill Traynor]

On Tue, Dec 18, 2012 at 7:28 AM, Biao <huanmateme at 163.com> wrote:

>
> At 2012-12-17 23:37:52,"Eren Türkay" <eren at hambedded.org> wrote:
> >On Mon, Dec 17, 2012 at 05:06:26PM +0800, Biao wrote:
> >> Greetings,
> >>
> >> I am a newbie tying to understand how bitbake works.
> >> There is one line as BBPATH = "${TOPDIR}" in the mybuild/conf/bblayers.conf, i would like to know where the TOPDIR is defined?
> >
> >It's defind in "lib/bb/parse/parse_py/ConfHandler.py:36". When TOPDIR is
> >not defined in any of the bitbake configuration files, it's set to
> >current working directory automatically.
> >
>
> The whole picture of how bitbake works is missing from the Manual of the bitbake, which typically should be(I guess) :
>
> 1. Set some environment variables like "TOPDIR, THISDIR..."
>
>
> 2. Looking for and parsing the conf/bblayers.conf.
>
> 3. Set the LAYERDIR and parsing each of the ONELAYER/conf/layer.conf
>
> 4. Locate and parsing the conf/bitbake.conf.
>
> 5. Go over of each of the .bb and setup all the global variables to get a dependency tree...
>
> 6. Start the build
>
> 7....
>
>
Have a look at the Bitbake section of the Yocto Project Reference manual
(Chapter 6), as it provides a little more information.

I am trying to draw a picture like the list above,which is from the
bitbake's point of view,
>
>  some of the list is not right, since lots things are still not clear to me. If someone could draw such picture, it helps a lot to understand the bitbake.
>
> >(...)
> >
> >def init(data):
> >    topdir = data.getVar('TOPDIR')
> >    if not topdir:
> >        data.setVar('TOPDIR', os.getcwd())
> >
> >(...)
> >
> >You may want to read the newly-written documentation about bitbake and
> >open embedded. I tried to explain how things fit together. I would like
> >to have your feedback.
> >
> >http://hambedded.org/blog/2012/11/24/from-bitbake-hello-world-to-an-image/
>
> I will try to give some feedback after finishing the reading.
>
> But for now, there are some silly questions:
>
> 1. There is a base_do_fetch() {}, I did not find the explanation of the keyword of 'base' in the manual, do i miss something?
>
> 2. There is 'bb.note' and 'bbnote' in the code example, is it a type-mistake or something else?
>
> >
> >--
> >    . 73! DE TA1AET
> >      http://linkedin.com/in/erenturkay
>
>
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>
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