Can we make single driver file for WFP callout and minifilter?

Can we implement WFP callout and minifilter in a single sys file?

As far as I know, yes you can combine them. WFP doesn’t have any opinions on where your callout comes from; it does not take over your DRIVER_OBJECT. But nobody in Windows appears to have actually done this, so I might be overlooking some little gotcha.

Also, just because you can doesn’t mean you should. If you have separate drivers, then it’s easier to start & stop them independently, you can more clearly separate out crashdumps/callstacks, and you can version/update/certify them independently. (I’m not trying to tell you what to do; I don’t know anything about your situation. I’m just offering some points for you to consider. There are valid situations where you do want to minimize the number of drivers.)