drm/i915/dvo: implement get_hw_state

Similar to the sdvo code we poke the dvo encoder whether the output is
active. Safe that dvo encoders are not standardized, so this requires
a new callback into the dvo chip driver.

Hence implement that for all 6 dvo drivers.

v2: With the newly added ns2501 we now have 6 dvo drivers instead of
just 5 ...

Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/dvo_sil164.c b/drivers/gpu/drm/i915/dvo_sil164.c
index cc24c1c..4debd32 100644
--- a/drivers/gpu/drm/i915/dvo_sil164.c
+++ b/drivers/gpu/drm/i915/dvo_sil164.c
@@ -226,6 +226,21 @@
 	return;
 }
 
+static bool sil164_get_hw_state(struct intel_dvo_device *dvo)
+{
+	int ret;
+	unsigned char ch;
+
+	ret = sil164_readb(dvo, SIL164_REG8, &ch);
+	if (ret == false)
+		return false;
+
+	if (ch & SIL164_8_PD)
+		return true;
+	else
+		return false;
+}
+
 static void sil164_dump_regs(struct intel_dvo_device *dvo)
 {
 	uint8_t val;
@@ -258,6 +273,7 @@
 	.mode_valid = sil164_mode_valid,
 	.mode_set = sil164_mode_set,
 	.dpms = sil164_dpms,
+	.get_hw_state = sil164_get_hw_state,
 	.dump_regs = sil164_dump_regs,
 	.destroy = sil164_destroy,
 };