Web Hob will have a whole page dedicated to build configuration
information. The page has 2 sections:

* A summary section that will show you things like target(s), machine,
distro, distro version, build system, target system, etc (for a full list,
see the file attached to bug 4259)

* A BitBake variables section, that will showŠ well: we don't know: that's
the subject of this email

In general, the variables section is supposed to show you a table with
variables set in your .conf files. That table would include things like
the variable key, a human-friendly version of that key, the variable
value, the file where is set, an explanation of each variable taken from
the project documentation, if the variable value was changed from the YP
defaults, if a value is overridden by another value set for the same
variable in a different .conf file, etc. I also suggested that all
variables set in any .conf file should be included in that table.

The development team have raised a few issues with the above:

1) This is effectively the output of bitbake -e, and it is a big set of
information.

2) We'll need to have build history enabled to gather the information,
with the subsequent impact on performance.

3) We'll be exposing variables that should not be edited (for example,
most of the stuff in bitbake.conf).

4) We'll need to update documentation.conf in order to provide
human-readable names for variables and short descriptions.

They suggested we create a "white list" of variables and display key,
value and file information.

I am not particularly satisfied with this, and the reason is the feedback
gathered from the user base during the high-level design phase. What I
heard was:

1) This configuration page was regarded as one of the most useful

2) The main advantage came from providing visibility of variables within
the same location, instead of having to go 'hunting' through the different
.conf files

3) People asked for the ability to show only variables edited by the user
in order to easily locate the cause of problems

4) People asked for the ability to see all places where the same variable
was set, and if one of the values was overridden by another.

5) My impression from the user base is that they don't need handholding
(which is what a 'white list' of variables curated by us would effectively
do). What they need is easy and well-structured access to information, so
that they can get a complete picture that helps them understand what's
going on. Just a couple of quotes from the interviews that illustrate this
point:

"Will you be able to search for any variables set in Bitbake?"

"What you are showing are the basic ones, but there are loads of them in
the framework and some of them are barely known. Right now we are working
on command line and we have to search the manual"

Another example is a very recent thread on the mailing list when someone's
problem could be addressed by setting the KBRANCH variable, which they
didn't know existed:

"I didn't know about the KBRANCH variable.  That sure helped (Š) KBRANCH
is documented; I found it in the mega-manual after the fact.  It's just a
variable I hadn't used yet so I didn't know to look for it.  No amount of
documentation can fix that problem."

In-depth, structured information can help with this "discoverability"
problem.

6) Yes, it might be a lot of information, but Web Hob tables provide
pretty powerful content customisation, search and filtering capabilities
that allow people to find specific content and / or display subsets of
information quite easily.

Some stuff we could do:

1) To manage the performance impact, turn this into a preference that you
can turn on or off.

2) To manage the amount of information, we could apply a filter to the
table by default, so that when users load it they only see a subset of the
information, but they can see the full content by resetting the filter.
Although, after looking at the output of bitbake -e, if you display only
the key / value pairs it doesn't seem to me that much. I could be totally
wrong though.


3) Your suggestions here.

Thanks,

Belen

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