iosys-map doc

/**                                                                              
 * iosys_map_rd_field - Read a member from a struct in the iosys_map             
 *                                                                               
 * @map__:              The iosys_map structure                                  
 * @struct_offset__:    Offset from the beggining of the map, where the struct   
 *                      is located                                               
 * @struct_type__:      The struct describing the layout of the mapping          
 * @field__:            Member of the struct to read                             
 *                                                                               
 * Read a value from iosys_map assuming its layout is described by a struct,     
 * starting on ``struct_offset__``. The offset and size to the struct member is  
 * calculated and possible un-aligned accesses to the mapping handled. This is   
 * the expected memory layout::                                                  
 *                                                                               
 *   Mapped buffer      <- iosys_map points here                                 
 *                                                                               
 *   struct foo {       <- struct offset to what is being read                   
 *      ...                                                                      
 *      ...                                                                      
 *      field;          <- field to read and return the value                    
 *      ...                                                                      
 *      ...                                                                      
 *   }                                                                           
 *                                                                               
 * Returns:                                                                      
 * The value read from the mapping.                                              
 */                                                                              
#define iosys_map_rd_field(map__, struct_offset__, struct_type__, field__) ({   \
        struct_type__ *s;                                                       \
        iosys_map_rd(map__, struct_offset__ + offsetof(struct_type__, field__), \
                     typeof(s->field__));                                       \
})