[bitbake-devel] [PATCH] Documentation: Add examples to User Manual, Metadata chapter

[Robert P. J. Day]

Signed-off-by: Robert P. J. Day <rpjday at crashcourse.ca>

---

  as long as i've understood everything correctly, this is just
throwing in some physical examples of a couple concepts.

diff --git a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
index a9f5072..423d9a4 100644
--- a/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
+++ b/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -285,6 +285,16 @@
                 The flags are immediately set to "abc" and "123", respectively.
                 The <filename>a</filename> flag becomes "abc456".
             </para>
+
+            <para>
+                Note that there is no need to pre-define variable flags; you
+                can simply start using them.  One extremely common application
+                is to attach some brief documentation to a BitBake variable as
+                follows:
+                <literallayout class='monospaced'>
+    CACHE[doc] = "The directory holding the cache of the metadata."
+                </literallayout>
+            </para>
         </section>

         <section id='inline-python-variable-expansion'>
@@ -298,7 +308,19 @@
      DATE = "${@time.strftime('%Y%m%d',time.gmtime())}"
                 </literallayout>
                 This example results in the <filename>DATE</filename>
-                variable becoming the current date.
+                variable being set to the current date.
+            </para>
+
+            <para>
+                Probably the most common use of this feature is to extract
+                the value of variables from BitBake's internal data dictionary,
+                <filename>d</filename>. The following lines
+                select the values of, respectively, a package name and its
+                version number:
+                <literallayout class='monospaced'>
+    PN = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE'),d)[0] or 'defaultpkgname'}"
+    PV = "${@bb.parse.BBHandler.vars_from_file(d.getVar('FILE'),d)[1] or '1.0'}"
+                </literallayout>
             </para>
         </section>


-- 

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Robert P. J. Day                                 Ottawa, Ontario, CANADA
                        http://crashcourse.ca

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
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