Work-around: Extract led name from device path

udev rule for leds subsystem in Witherspoon launches a systemd
service file with /sys/class/leds/$name. If the path is
sys-class-leds-rear-fault, systemd service file
interprets it as /sys/class/leds/rear/fault.

However, what is really needed by the service file is
/sys/class/leds/rear-fault.

This is a limitation in current systemd with template argument
containing hyphen.

Short term solution is to extract $name from path
and convert "/" to "-".  It would then become:
/sys/class/leds/rear-fault and hence will work.

Refer: systemd/systemd#5072

Change-Id: I0acc11d039650857005ba75810e3ef6bcc4a3934
Signed-off-by: Vishwanatha Subbanna <vishwa@linux.vnet.ibm.com>

2 files changed, 21 insertions, 8 deletions

diff --git a/configure.ac b/configure.ac
index 02472d0..6a08be3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,6 +36,11 @@ AC_ARG_VAR(OBJPATH, [The physical LED controller Dbus root])
 AS_IF([test "x$OBJPATH" == "x"], [OBJPATH="/xyz/openbmc_project/led/physical"])
 AC_DEFINE_UNQUOTED([OBJPATH], ["$OBJPATH"], [The physical LED controller Dbus root])
 
+# Platform device path for led subsystem.
+AC_ARG_VAR(DEVPATH, [Physical led device path])
+AS_IF([test "x$DEVPATH" == "x"], [DEVPATH="/sys/class/leds/"])
+AC_DEFINE_UNQUOTED([DEVPATH], ["$DEVPATH"], [Physical led device path])
+
 # Create configured output
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT
diff --git a/controller.cpp b/controller.cpp
index d5728da..f0ba4c2 100644
--- a/controller.cpp
+++ b/controller.cpp
@@ -41,15 +41,23 @@ int main(int argc, char** argv)
         ExitWithError("Path not specified.", argv);
     }
 
-    // Extract the name of LED from path.
-    auto index = path.rfind("/");
-    if (index == std::string::npos)
-    {
-        throw std::runtime_error("No Led in " + path);
-    }
+    // If the LED has a hyphen in the name like: "one-two", then it gets passed
+    // as /one/two/ as opposed to /one-two to the service file. There is a
+    // change needed in systemd to solve this issue and hence putting in this
+    // work-around.
+
+    // Since this application always gets invoked as part of a udev rule,
+    // it is always guaranteed to get /sys/class/leds/one/two
+    // and we can go beyond leds/ to get the actual led name.
+    // Refer: systemd/systemd#5072
 
-    // Remove the leading "/"
-    auto name = path.substr(index + 1);
+    // On an error, this throws an exception and terminates.
+    auto name = path.substr(strlen(DEVPATH));
+
+    // LED names may have a hyphen and that would be an issue for
+    // dbus paths and hence need to convert them to underscores.
+    std::replace(name.begin(), name.end(), '/', '-');
+    path = std::move(DEVPATH + name);
 
     // Convert to lowercase just in case some are not and that
     // we follow lowercase all over