kindle: detect if launcher script has changed

And a complete restart from the parent launcher (e.g. KUAL) is needed.

frontend/device/kindle/device.lua

@@ -782,6 +782,12 @@ function Kindle:readyToSuspend(delay)
     self.suspend_time = time.boottime_or_realtime_coarse()
 end
 
+function Kindle:isStartupScriptUpToDate()
+    local md5 = require("ffi/MD5")
+    -- Compare the hash of the *active* script to the *potential* one.
+    return md5.sumFile("/var/tmp/koreader.sh") == md5.sumFile(os.getenv("KOREADER_DIR") .. "/koreader.sh")
+end
+
 function Kindle:UIManagerReady(uimgr)
     UIManager = uimgr
 end

platform/kindle/koreader.sh

@@ -4,6 +4,9 @@
 # living in a magical land that doesn't suffer from gross filesystem deficiencies.
 # Otherwise, the vfat+fuse mess means an OTA update will break the script on exit,
 # and potentially leave the user in a broken state, with the WM still paused...
+# Additionally, this is used by KOReader to detect if the original script has
+# changed after an update (requiring a complete restart from the parent
+# launcher).
 if [ "$(dirname "${0}")" != "/var/tmp" ]; then
     cp -pf "${0}" /var/tmp/koreader.sh
     chmod 777 /var/tmp/koreader.sh