configure: differ between check and yes/no

So far one could only specify yes/no (optionally for all drivers through
--enable-all-drivers={yes,no}). However, even when stating a =yes, the
dependency check would override it to a =no if the dependencies are
missing.

This is a bit annoying for scripts since a script may specify
--enable-foo-driver=yes but in fact the build may not contain
`foo-driver` due to missing build dependencies. This is especially
problematic for distro's which look like they currently do not build a
defined driver set - which results in random drivers missing [1].

This fixes that by following the autoconf examples [2] that allow a third
state `check`. With that `no` means no, `yes` means yes (raise an error
if deps are unavailable) and `check` gracefully disables drivers with
unavailable dependencies.

With that --enable-all-drivers can be used to ensure that all drivers are
built in. Certain drivers can still be explicitly disabled by overriding
the individual driver setting.

This way distros can specify --enable-all-drivers and new drivers with
unmet dependencies will cause an error rather than silently getting
dropped of the build.

[1] https://sigrok.org/bugzilla/show_bug.cgi?id=1699
[2] https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/External-Software.html#External-Software

To: sigrok-devel@lists.sourceforge.net
Cc: Daniel Thompson <redacted>

diff --git a/configure.ac b/configure.ac
index cbde1480ea87ad3d4ca0538551b700c84c8ca331..b282a5fb0c5d89e144a2d8aa8fd4faa266e2e998 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -281,8 +281,8 @@ sr_check_driver_deps() {
 
 AC_ARG_ENABLE([all-drivers],
        [AS_HELP_STRING([--enable-all-drivers],
-                       [enable all drivers by default [default=yes]])],
-       [], [enable_all_drivers=yes])
+                       [enable all drivers by default [default=check]])],
+       [], [enable_all_drivers=check])
 
 ## _SR_DRIVER(Device name, driver-name, var-name, [dependencies...])
 m4_define([_SR_DRIVER], [
@@ -290,9 +290,14 @@ m4_define([_SR_DRIVER], [
                [AS_HELP_STRING([--enable-$2], [enable $1 support])],
                [$3=$enableval], [$3=$enable_all_drivers])
 
-       AS_IF([test "x[$]$3" = xyes], [sr_hw_info=yes[]m4_ifval([$4], [
+       AS_IF([test "x[$]$3" != xno],
+               [sr_hw_info=yes[]m4_ifval([$4], [
                sr_check_driver_deps $4 \
-                       || $3=no sr_hw_info="no (missing: $sr_deps_missing)"
+                       || if test "x[$]$3" != xcheck; then
+                               AC_MSG_ERROR([driver $2 is enabled, but deps are missing: $sr_deps_missing])
+                       else
+                               $3=no sr_hw_info="no (missing: $sr_deps_missing)"
+                       fi;
        ])], [sr_hw_info='no (disabled)'])
        sr_driver_summary_append "$2" "$sr_hw_info"