kbuild: make *config usage docs

Create a kconfig user assistance guide, with a few tips and hints
about using menuconfig, xconfig, and gconfig.

Mostly contains user interface, environment variables, and search topics,
along with mini.config/custom.config usage.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 20 insertions, 12 deletions

diff --git a/README b/README
index 159912cf5155..90a07658ede1 100644
--- a/README
+++ b/README
@@ -52,11 +52,11 @@ DOCUMENTATION:
 
  - The Documentation/DocBook/ subdirectory contains several guides for
    kernel developers and users.  These guides can be rendered in a
-   number of formats:  PostScript (.ps), PDF, and HTML, among others.
-   After installation, "make psdocs", "make pdfdocs", or "make htmldocs"
-   will render the documentation in the requested format.
+   number of formats:  PostScript (.ps), PDF, HTML, & man-pages, among others.
+   After installation, "make psdocs", "make pdfdocs", "make htmldocs",
+   or "make mandocs" will render the documentation in the requested format.
 
-INSTALLING the kernel:
+INSTALLING the kernel source:
 
  - If you install the full sources, put the kernel tarball in a
    directory where you have permissions (eg. your home directory) and
@@ -187,14 +187,9 @@ CONFIGURING the kernel:
         "make randconfig"  Create a ./.config file by setting symbol
                            values to random values.
 
-   The allyesconfig/allmodconfig/allnoconfig/randconfig variants can
-   also use the environment variable KCONFIG_ALLCONFIG to specify a
-   filename that contains config options that the user requires to be
-   set to a specific value.  If KCONFIG_ALLCONFIG=filename is not used,
-   "make *config" checks for a file named "all{yes/mod/no/random}.config"
-   for symbol values that are to be forced.  If this file is not found,
-   it checks for a file named "all.config" to contain forced values.
-   
+   You can find more information on using the Linux kernel config tools
+   in Documentation/kbuild/make-configs.txt.
+
         NOTES on "make config":
         - having unnecessary drivers will make the kernel bigger, and can
           under some circumstances lead to problems: probing for a
@@ -231,6 +226,19 @@ COMPILING the kernel:
  - If you configured any of the parts of the kernel as `modules', you
    will also have to do "make modules_install".
 
+ - Verbose kernel compile/build output:
+
+   Normally the kernel build system runs in a fairly quiet mode (but not
+   totally silent).  However, sometimes you or other kernel developers need
+   to see compile, link, or other commands exactly as they are executed.
+   For this, use "verbose" build mode.  This is done by inserting
+   "V=1" in the "make" command.  E.g.:
+
+        make V=1 all
+
+   To have the build system also tell the reason for the rebuild of each
+   target, use "V=2".  The default is "V=0".
+
  - Keep a backup kernel handy in case something goes wrong.  This is 
    especially true for the development releases, since each new release
    contains new code which has not been debugged.  Make sure you keep a