explain Kconfig recipe better, adjust existing code

The Kconfig recipes for backporting need a bit more
explanation, add that. Also adjust the existing ones.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

diff --git a/backport/compat/Kconfig b/backport/compat/Kconfig
index 5a9b303d2b10dbc57d67f7253f53878bd7cf38fe..0edd2fb6cfc6d9b048a7e15446d915fe1c8064d6 100644 (file)
--- a/backport/compat/Kconfig
+++ b/backport/compat/Kconfig
@@ -12,7 +12,24 @@
 #
 # config BACKPORT_BUILD_FOO
 #      tristate
-#      default m if BACKPORT_FOO && !FOO
+#      # or bool
+#
+#      # not possible on kernel < X.Y, build will fail if any
+#      # drivers are allowed to build on kernels < X.Y
+#      depends on BACKPORT_KERNEL_X_Y
+#
+#      # don't build the backport code if FOO is in the kernel
+#      # already, but only if the kernel version is also >= X.Z;
+#      # this is an example of backporting where the version of
+#      # the FOO subsystem that we need is only available from
+#      # kernel version X.Z
+#      depends on !FOO || BACKPORT_KERNEL_X_Z
+#
+#      # build if driver needs it (it selects BACKPORT_FOO)
+#      default m if BACKPORT_FOO
+#
+#      # or for build-testing (BACKPORT_USERSEL_BUILD_ALL is enabled)
+#      default m if BACKPORT_USERSEL_BUILD_ALL
 #
 # config BACKPORT_FOO
 #      bool
@@ -69,7 +86,8 @@ config BACKPORT_BUILD_KFIFO
 
 config BACKPORT_BUILD_CORDIC
        tristate
-       default m if BACKPORT_CORDIC && !CORDIC
+       depends on !CORDIC
+       default m if BACKPORT_CORDIC
        default m if BACKPORT_USERSEL_BUILD_ALL
 
 config BACKPORT_CORDIC
@@ -77,7 +95,8 @@ config BACKPORT_CORDIC
 
 config BACKPORT_BUILD_CRC8
        tristate
-       default m if BACKPORT_CRC8 && !CRC8
+       depends on !CRC8
+       default m if BACKPORT_CRC8
        default m if BACKPORT_USERSEL_BUILD_ALL
 
 config BACKPORT_CRC8
@@ -94,8 +113,9 @@ config BACKPORT_OPTION_BT_SOCK_CREATE_NEEDS_KERN
 
 config BACKPORT_BUILD_AVERAGE
        bool
+       depends on !AVERAGE
        default y if BACKPORT_USERSEL_BUILD_ALL
-       default y if !AVERAGE && BACKPORT_AVERAGE
+       default y if BACKPORT_AVERAGE
 
 config BACKPORT_AVERAGE
        bool