kernel-dev: Updated changing the configuration section.

Robert P. J. Day pointed out some implied meanings in this section
that indicate configurations from .config are exclusive somehow
from configurations applied through config fragments.  That is
not the case.  I have inserted a note to clear up that implied
meaning.

Reported-by: Robert P. J. Day <rpjday@crashcourse.ca>
(From yocto-docs rev: 5ac27e8a2aea662a8e70dda0e852b5ea401b8b00)

Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 27 insertions, 15 deletions

diff --git a/documentation/kernel-dev/kernel-dev-common.xml b/documentation/kernel-dev/kernel-dev-common.xml
index f0e95aca07..6f39a70dff 100644
--- a/documentation/kernel-dev/kernel-dev-common.xml
+++ b/documentation/kernel-dev/kernel-dev-common.xml
@@ -148,16 +148,16 @@
             <para>
                 You can make wholesale or incremental changes to the Linux
                 kernel <filename>.config</filename> file by including a
-                <filename>defconfig</filename> or by specifying
-                configuration fragments in the 
+                <filename>defconfig</filename> and by specifying
+                configuration fragments in the
                 <ulink url='&YOCTO_DOCS_REF_URL;#var-SRC_URI'><filename>SRC_URI</filename></ulink>.
             </para>
 
             <para>
-                If you have a complete Linux kernel <filename>.config</filename>
-                file you want to use, copy it to a directory named 
-                <filename>files</filename>, which must be in 
-                your layer's <filename>recipes-kernel/linux</filename> 
+                If you have a final Linux kernel <filename>.config</filename>
+                file you want to use, copy it to a directory named
+                <filename>files</filename>, which must be in
+                your layer's <filename>recipes-kernel/linux</filename>
                 directory, and name the file "defconfig".
                 Then, add the following lines to your linux-yocto
                 <filename>.bbappend</filename> file in your layer:
@@ -165,24 +165,36 @@
      FILESEXTRAPATHS_prepend := "${THISDIR}/files:"
      SRC_URI += "file://defconfig"
                 </literallayout>
-                The 
-                <filename>SRC_URI</filename> tells the build system how to 
-                search for the file, while the 
+                The <filename>SRC_URI</filename> tells the build system how to
+                search for the file, while the
                 <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESEXTRAPATHS'><filename>FILESEXTRAPATHS</filename></ulink>
-                extends the 
+                extends the
                 <ulink url='&YOCTO_DOCS_REF_URL;#var-FILESPATH'><filename>FILESPATH</filename></ulink>
-                variable (search directories) to include the 
+                variable (search directories) to include the
                 <filename>files</filename> directory you created for the
                 configuration changes.
             </para>
 
+            <note>
+                The build system applies the configurations from the
+                <filename>.config</filename> file before applying any
+                subsequent configuration fragments.
+                The final kernel configuration is a combination of the
+                configurations in the <filename>.config</filename> file and
+                any configuration fragments you provide.
+                You need to realize that if you have any configuration
+                fragments, the build system applies these on top of and
+                after applying the existing <filename>.config</filename>
+                file configurations.
+            </note>
+
             <para>
                 Generally speaking, the preferred approach is to determine the
                 incremental change you want to make and add that as a
                 configuration fragment.
                 For example, if you want to add support for a basic serial
-                console, create a file named <filename>8250.cfg</filename> in the
-                <filename>files</filename> directory with the following
+                console, create a file named <filename>8250.cfg</filename> in
+                the <filename>files</filename> directory with the following
                 content (without indentation):
                 <literallayout class='monospaced'>
      CONFIG_SERIAL_8250=y
@@ -193,8 +205,8 @@
      CONFIG_SERIAL_CORE=y
      CONFIG_SERIAL_CORE_CONSOLE=y
                 </literallayout>
-                Next, include this configuration fragment and extend the 
-                <filename>FILESPATH</filename> variable in your 
+                Next, include this configuration fragment and extend the
+                <filename>FILESPATH</filename> variable in your
                 <filename>.bbappend</filename> file:
                 <literallayout class='monospaced'>
      FILESEXTRAPATHS_prepend := "${THISDIR}/files:"