DM368 EVM Watchdog - set timeout

Hello.
I shall be very thankful on a comment about the watchdog driver provided by TI in linux_2.6.18_pro500.
It seems not to have the ability to set the watchdog strike time.
Looking into the file linux/watchdog.h I found the WDIOC_SETTIMEOUT ioctl. but I do not see it in the driver implemented.
So, I have simple questions:
1. Is it not implemented on purpose or simply because of the lack of time?
2. If the second is correct, will the following implementation be sufficient:
case WDIOC_SETTIMEOUT:
    davinci_wdt_release(inode,file);
    heartbeat = arg;
    wdt_enable();
    break;


Many thanks ahead for any comment.