config_cpu: set ondemand governor only if available

Nowadays we enable and use the ondemand governor by default in
our kernel configuration. More recent systems providing Intel
Haswell CPUs (e.g. the i7-3520M CPU as present in the Lenovo X230
laptops as well as the CPU present in IBM flex chassis) use
pstates/intel_pstate and disable the ondemand governor at all, so
only performance and powersave are available (unless you set
intel_pstate=disable at boot time).

Also see https://plus.google.com/+TheodoreTso/posts/2vEekAsG2QT
Thanks to Yves-Alexis Perez for the pointer.

diff --git a/autoconfig.functions b/autoconfig.functions
index 3ab2c02..23574ef 100755 (executable)
--- a/autoconfig.functions
+++ b/autoconfig.functions
@@ -1028,22 +1028,22 @@ if [ -x /etc/init.d/loadcpufreq ] ; then
       fi
    fi
 
-   rm -f $LOADCPUFREQ
+   rm -f "$LOADCPUFREQ"
 
    if [ -z "$SKIP_CPU_GOVERNOR" ] ; then
-     if grep -vq ondemand /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors; then
-       einfo "Loading cpufreq_ondemand"
-       modprobe cpufreq_ondemand
-       eend $?
+     if [ -r /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors ] ; then
+       if ! grep -q ondemand /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors ; then
+         einfo "Ondemand governor not available for CPU(s), not modifying governor configuration"
+       else
+         einfo "Setting ondemand governor"
+         RC=0
+         for file in $(find /sys/devices/system/cpu/ -name scaling_governor 2>/dev/null) ; do
+           echo ondemand > $file || RC=1
+         done
+         eend $RC
+       fi
      fi
-
-     einfo "Setting ondemand governor"
-     RC=0
-     for file in $(find /sys/devices/system/cpu/ -name scaling_governor 2>/dev/null) ; do
-       echo ondemand > $file || RC=1
-     done
-     eend $RC
-   fi # cpu-governor
+   fi
 
    eoutdent
 fi