832 /** * enable_vblank - enable vblank interrupt events * @dev: DRM device * @crtc: which irq to enable * * Enable vblank interrupts for @crtc. If the device doesn't have * a hardware vblank counter, this routine should be a no-op, since * interrupts will have to stay on to keep the count accurate. * * RETURNS * Zero on success, appropriate errno if the given @crtc's vblank * interrupt cannot be enabled. */