TRANS_DP_CTL
i915_reg_t reg = TRANS_DP_CTL(pipe);
reg = TRANS_DP_CTL(pipe);
trans_dp = I915_READ(TRANS_DP_CTL(crtc->pipe));
I915_WRITE(TRANS_DP_CTL(crtc->pipe), trans_dp);
u32 val = I915_READ(TRANS_DP_CTL(p));
u32 trans_dp = I915_READ(TRANS_DP_CTL(crtc->pipe));