Name
v4l2_ctrl_add_handler — 
     Add all controls from handler add to handler hdl.
 
Arguments
- hdl
- 
     The control handler.
     
- add
- 
     The control handler whose controls you want to add to
     the - hdlcontrol handler.
 
- filter
- 
     This function will filter which controls should be added.
     
Description
   Does nothing if either of the two handlers is a NULL pointer.
   If filter is NULL, then all controls are added. Otherwise only those
   controls for which filter returns true will be added.
   In case of an error hdl->error will be set to the error code (if it
   wasn't set already).