H_DISPLAY_2PIX
if( h_display > H_DISPLAY_2PIX( RADEON_CRTC_H_DISP >> RADEON_CRTC_H_DISP_SHIFT ) )
h_display = H_DISPLAY_2PIX( RADEON_CRTC_H_DISP >> RADEON_CRTC_H_DISP_SHIFT );
h_display = H_DISPLAY_2PIX( H_DISPLAY_2REG( h_display ));