[linux-dvb] What is __user in dvb_apps ???

[clemens at dwf.com]

What is this in /include/linux/dvb/osd.h

        void __user *data;

and in /include/linux/dvb/video.h

        char __user *iFrame;

I dont understnd what __user is suposed to be (it doesnt appear anywhere else)
and neither does the compiler...
Where is this thing (supposed to be) defined?

                                Reg.Clemens
                                reg at dwf.com