RADEON_CRTC_H_DISP
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 );
| (((mode->timing.h_display / 8 - 1) << RADEON_CRTC_H_DISP_SHIFT) & RADEON_CRTC_H_DISP);
b = (r & RADEON_CRTC_H_DISP) >> RADEON_CRTC_H_DISP_SHIFT;