epkowa: added Perfection V500 support

pkgs/misc/drivers/epkowa/default.nix

@@ -25,6 +25,37 @@ in
 # adding a plugin for another printer shouldn't be too difficult, but you need the firmware to test...
 
 let plugins = {
+  x770 =   stdenv.mkDerivation rec {
+    name = "iscan-gt-x770-bundle";
+    version = "1.0.1";
+    pluginVersion = "2.1.2-1";
+
+    buildInputs = [ patchelf rpm ];
+    src = fetchurl {
+      url = "https://download2.ebz.epson.net/iscan/plugin/gt-x770/rpm/x64/iscan-gt-x770-bundle-${version}.x64.rpm.tar.gz";
+      sha256 = "0m9c60rszzdvq1pqfzygzzrjycm1giy465lj29108j7hsnfcv56r";
+    };
+    installPhase = ''
+      cd plugins
+      ${rpm}/bin/rpm2cpio iscan-plugin-gt-x770-${pluginVersion}.x86_64.rpm | ${cpio}/bin/cpio -idmv
+      mkdir $out
+      cp -r usr/share $out
+      cp -r usr/lib64 $out/lib
+      mv $out/share/iscan $out/share/esci
+      mv $out/lib/iscan $out/lib/esci
+      '';
+    preFixup = ''
+      lib=$out/lib/esci/libesint7C.so
+      rpath=${gcc.cc.lib}/lib/
+      patchelf --set-rpath $rpath $lib
+      '';
+    passthru = {
+      registrationCommand = ''
+        $registry --add interpreter usb 0x04b8 0x0130 "$plugin/lib/esci/libesint7C $plugin/share/esci/esfw7C.bin"
+        '';
+      hw = "Perfection V500 Photo";
+      };
+    };
   f720 = stdenv.mkDerivation rec {
     name = "iscan-gt-f720-bundle";
     version = "1.0.1";

pkgs/misc/drivers/epkowa/firmware_location.patch

@@ -8,11 +8,12 @@ set this environment variable. Instead, we patch iscan to set this variable
 before loading libesci-interpreter-gt-f720.so.
 --- backend/channel-usb.c.orig	2017-08-14 11:24:27.669582456 +0200
 +++ backend/channel-usb.c	2017-08-14 11:31:40.509010897 +0200
-@@ -169,6 +169,8 @@
+@@ -169,6 +169,9 @@
  {
    SANE_Status s;
  
 +  setenv("ESCI_FIRMWARE_DIR", NIX_ESCI_PREFIX, 1);
++  setenv("ISCAN_FW_DIR", NIX_ESCI_PREFIX, 1);
 +
    s = sanei_usb_open (self->name, &self->fd);