diff --git a/src/minivhd.h b/src/minivhd.h
index 9bbd428..216936a 100644
--- a/src/minivhd.h
+++ b/src/minivhd.h
@@ -19,6 +19,12 @@ typedef enum MVHDError {
     MVHD_ERR_SPARSE_CHECKSUM
 } MVHDError;
 
+typedef struct MVHDGeom {
+    uint16_t cyl;
+    uint8_t heads;
+    uint8_t spt;
+} MVHDGeom;
+
 typedef struct MVHDMeta {
     FILE* f;
     char* filename;
@@ -29,11 +35,11 @@ typedef struct MVHDMeta {
 } MVHDMeta;
 
 MVHDMeta* mvhd_open(const char* path, int* err);
-MVHDMeta* mvhd_create_fixed(const char* path, int cyl, int heads, int spt, int* err);
-MVHDMeta* mvhd_create_sparse(const char* path, int cyl, int heads, int spt, int* err);
-MVHDMeta* mvhd_create_diff(const char* path, const char* par_path, int cyl, int heads, int spt, int* err);
+MVHDMeta* mvhd_create_fixed(const char* path, MVHDGeom geom, int* err);
+MVHDMeta* mvhd_create_sparse(const char* path, MVHDGeom geom, int* err);
+MVHDMeta* mvhd_create_diff(const char* path, const char* par_path, MVHDGeom geom, int* err);
 void mvhd_close(MVHDMeta* vhdm);
-void mvhd_calculate_geometry(int size_mb, int* new_size, int* cyl, int* heads, int* spt);
+MVHDGeom mvhd_calculate_geometry(int size_mb, int* new_size);
 int mvhd_read_sectors(MVHDMeta* vhdm, int offset, int num_sectors, void* out_buff);
 int mvhd_write_sectors(MVHDMeta* vhdm, int offset, int num_sectors, void* in_buff);
 int mvhd_format_sectors(MVHDMeta* vhdm, int offset, int num_sectors);