* requirements on the fourth parameter, so a private implementation
  * instead of using acpi_check_dsm().
  */
-static int nouveau_check_optimus_dsm(acpi_handle handle)
+static int nouveau_dsm_get_optimus_functions(acpi_handle handle)
 {
        int result;
 
         * ACPI Spec v4 9.14.1: if bit 0 is zero, no function is supported.
         * If the n-th bit is enabled, function n is supported
         */
-       return result & 1 && result & (1 << NOUVEAU_DSM_OPTIMUS_CAPS);
+       if (result & 1 && result & (1 << NOUVEAU_DSM_OPTIMUS_CAPS))
+               return result;
+       return 0;
 }
 
 static int nouveau_dsm(acpi_handle handle, int func, int arg)
 {
        acpi_handle dhandle;
        bool supports_mux;
-       bool supports_opt;
+       int optimus_funcs;
 
        dhandle = ACPI_HANDLE(&pdev->dev);
        if (!dhandle)
 
        supports_mux = acpi_check_dsm(dhandle, nouveau_dsm_muid, 0x00000102,
                                      1 << NOUVEAU_DSM_POWER);
-       supports_opt = nouveau_check_optimus_dsm(dhandle);
+       optimus_funcs = nouveau_dsm_get_optimus_functions(dhandle);
 
        /* Does not look like a Nvidia device. */
-       if (!supports_mux && !supports_opt)
+       if (!supports_mux && !optimus_funcs)
                return;
 
        *dhandle_out = dhandle;
        *has_mux = supports_mux;
-       *has_opt = supports_opt;
+       *has_opt = !!optimus_funcs;
 
-       if (supports_opt) {
+       if (optimus_funcs) {
                uint32_t result;
                nouveau_optimus_dsm(dhandle, NOUVEAU_DSM_OPTIMUS_CAPS, 0,
                                    &result);