[PATCH 2/6] drm: Factor out drm_dp_dual_mode_read_regs()

[Imre Deak]

In follow-up patches we'll read out more registers and add a new step to
read them out in one go, so factor out the read-out part to keep things
clean at the end.

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/drm_dp_dual_mode_helper.c | 91 +++++++++++++++++++------------
 include/drm/drm_dp_dual_mode_helper.h     |  5 ++
 2 files changed, 60 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
index 1764203..1cb6c15 100644
--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
@@ -161,6 +161,39 @@ static bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
 		 DP_DUAL_MODE_TYPE_HAS_DPCD));
 }
 
+static int drm_dp_dual_mode_read_regs(struct drm_dp_dual_mode_adaptor *adaptor)
+{
+	struct drm_dp_dual_mode_regs *regs = &adaptor->regs;
+	ssize_t ret;
+
+	ret = drm_dp_dual_mode_read(adaptor, DP_DUAL_MODE_HDMI_ID,
+				    regs->hdmi_id, sizeof(regs->hdmi_id));
+	if (ret) {
+		DRM_DEBUG_KMS("Failed to read HDMI ID (%zd)\n", ret);
+		memset(regs, 0, sizeof(*regs));
+		return ret;
+	}
+
+	/*
+	 * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
+	 * the offset but ignore it, and instead they just always return
+	 * data from the start of the HDMI ID buffer.
+	 */
+	ret = drm_dp_dual_mode_read(adaptor, DP_DUAL_MODE_ADAPTOR_ID,
+				    &regs->adaptor_id,
+				    sizeof(regs->adaptor_id));
+	if (ret) {
+		DRM_DEBUG_KMS("Failed to read adaptor ID (%zd)\n", ret);
+		regs->adaptor_id = 0;
+	}
+
+	DRM_DEBUG_KMS("DP dual-mode: HDMI-ID %*pE adaptor-ID %#02x\n",
+		      (int)sizeof(regs->hdmi_id), regs->hdmi_id,
+		      regs->adaptor_id);
+
+	return 0;
+}
+
 /**
  * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
  * @adaptor: DP dual mode adaptor
@@ -180,9 +213,7 @@ static bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
 void drm_dp_dual_mode_detect(struct drm_dp_dual_mode_adaptor *adaptor,
 			     struct i2c_adapter *i2c_adapter)
 {
-	char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
-	uint8_t adaptor_id = 0x00;
-	ssize_t ret;
+	struct drm_dp_dual_mode_regs *regs;
 
 	adaptor->i2c_adapter = i2c_adapter;
 	adaptor->type = DRM_DP_DUAL_MODE_UNKNOWN;
@@ -201,56 +232,44 @@ void drm_dp_dual_mode_detect(struct drm_dp_dual_mode_adaptor *adaptor,
 	 * port or a native HDMI port. Both of these methods are entirely
 	 * hardware/driver specific so we can't deal with them here.
 	 */
-	ret = drm_dp_dual_mode_read(adaptor, DP_DUAL_MODE_HDMI_ID,
-				    hdmi_id, sizeof(hdmi_id));
-	DRM_DEBUG_KMS("DP dual mode HDMI ID: %*pE (err %zd)\n",
-		      ret ? 0 : (int)sizeof(hdmi_id), hdmi_id, ret);
-	if (ret)
+	if (drm_dp_dual_mode_read_regs(adaptor))
 		return;
+	regs = &adaptor->regs;
 
 	/*
-	 * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
-	 * the offset but ignore it, and instead they just always return
-	 * data from the start of the HDMI ID buffer. So for a broken
-	 * type 1 HDMI adaptor a single byte read will always give us
-	 * 0x44, and for a type 1 DVI adaptor it should give 0x00
+	 * As noted in drm_dp_dual_mode_read_regs() on a broken type1
+	 * HDMI adaptor a single byte read of the
+	 * DP_DUAL_MODE_ADAPTOR_ID register will always give us 0x44,
+	 * and for a type 1 DVI adaptor it should give 0x00
 	 * (assuming it implements any registers). Fortunately neither
 	 * of those values will match the type 2 signature of the
 	 * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
 	 * the type 2 adaptor detection safely even in the presence
 	 * of broken type 1 adaptors.
 	 */
-	ret = drm_dp_dual_mode_read(adaptor, DP_DUAL_MODE_ADAPTOR_ID,
-				    &adaptor_id, sizeof(adaptor_id));
-	DRM_DEBUG_KMS("DP dual mode adaptor ID: %02x (err %zd)\n",
-		      adaptor_id, ret);
-	if (ret == 0) {
-		if (is_lspcon_adaptor(hdmi_id, adaptor_id)) {
-			adaptor->type = DRM_DP_DUAL_MODE_LSPCON;
-			return;
-		}
-		if (is_type2_adaptor(adaptor_id)) {
-			if (is_hdmi_adaptor(hdmi_id))
-				adaptor->type = DRM_DP_DUAL_MODE_TYPE2_HDMI;
-			else
-				adaptor->type = DRM_DP_DUAL_MODE_TYPE2_DVI;
-			return;
-		}
+	if (is_lspcon_adaptor(regs->hdmi_id, regs->adaptor_id)) {
+		adaptor->type = DRM_DP_DUAL_MODE_LSPCON;
+	} else if (is_type2_adaptor(regs->adaptor_id)) {
+		if (is_hdmi_adaptor(regs->hdmi_id))
+			adaptor->type = DRM_DP_DUAL_MODE_TYPE2_HDMI;
+		else
+			adaptor->type = DRM_DP_DUAL_MODE_TYPE2_DVI;
+	} else {
 		/*
 		 * If neither a proper type 1 ID nor a broken type 1 adaptor
 		 * as described above, assume type 1, but let the user know
 		 * that we may have misdetected the type.
 		 */
-		if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
+		if (!is_type1_adaptor(regs->adaptor_id) &&
+		    regs->adaptor_id != regs->hdmi_id[0])
 			DRM_ERROR("Unexpected DP dual mode adaptor ID %02x\n",
-				  adaptor_id);
+				  regs->adaptor_id);
 
+		if (is_hdmi_adaptor(regs->hdmi_id))
+			adaptor->type = DRM_DP_DUAL_MODE_TYPE1_HDMI;
+		else
+			adaptor->type = DRM_DP_DUAL_MODE_TYPE1_DVI;
 	}
-
-	if (is_hdmi_adaptor(hdmi_id))
-		adaptor->type = DRM_DP_DUAL_MODE_TYPE1_HDMI;
-	else
-		adaptor->type = DRM_DP_DUAL_MODE_TYPE1_DVI;
 }
 EXPORT_SYMBOL(drm_dp_dual_mode_detect);
 
diff --git a/include/drm/drm_dp_dual_mode_helper.h b/include/drm/drm_dp_dual_mode_helper.h
index a804d36..1436067 100644
--- a/include/drm/drm_dp_dual_mode_helper.h
+++ b/include/drm/drm_dp_dual_mode_helper.h
@@ -101,6 +101,11 @@ struct i2c_adapter;
 struct drm_dp_dual_mode_adaptor {
 	enum drm_dp_dual_mode_type type;
 	struct i2c_adapter *i2c_adapter;
+
+	struct drm_dp_dual_mode_regs {
+		uint8_t hdmi_id[16];
+		uint8_t adaptor_id;
+	} regs;
 };
 
 void drm_dp_dual_mode_detect(struct drm_dp_dual_mode_adaptor *adaptor,
-- 
2.5.0