[PATCH v4 1/4] drm/panel: Add helper for reading DT rotation

From: Derek Basehore <dbasehore@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <maxime.ripard@bootlin.com>,
	Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	Thierry Reding <thierry.reding@gmail.com>,
	Sam Ravnborg <sam@ravnborg.org>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>, CK Hu <ck.hu@mediatek.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	Derek Basehore <dbasehore@chromium.org>
Subject: [PATCH v4 1/4] drm/panel: Add helper for reading DT rotation
Date: Tue,  2 Jul 2019 16:42:55 -0700	[thread overview]
Message-ID: <20190702234258.136349-2-dbasehore@chromium.org> (raw)
In-Reply-To: <20190702234258.136349-1-dbasehore@chromium.org>

This adds a helper function for reading the rotation (panel
orientation) from the device tree.

Signed-off-by: Derek Basehore <dbasehore@chromium.org>
---
 drivers/gpu/drm/drm_panel.c | 43 +++++++++++++++++++++++++++++++++++++
 include/drm/drm_panel.h     |  7 ++++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index dbd5b873e8f2..169bab54d52d 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -172,6 +172,49 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np)
 	return ERR_PTR(-EPROBE_DEFER);
 }
 EXPORT_SYMBOL(of_drm_find_panel);
+
+/**
+ * of_drm_get_panel_orientation - look up the orientation of the panel through
+ * the "rotation" binding from a device tree node
+ * @np: device tree node of the panel
+ * @orientation: orientation enum to be filled in
+ *
+ * Looks up the rotation of a panel in the device tree. The orientation of the
+ * panel is expressed as a property name "rotation" in the device tree. The
+ * rotation in the device tree is counter clockwise.
+ *
+ * Return: 0 when a valid rotation value (0, 90, 180, or 270) is read or the
+ * rotation property doesn't exist. -EERROR otherwise.
+ */
+int of_drm_get_panel_orientation(const struct device_node *np,
+				 enum drm_panel_orientation *orientation)
+{
+	int rotation, ret;
+
+	ret = of_property_read_u32(np, "rotation", &rotation);
+	if (ret == -EINVAL) {
+		/* Don't return an error if there's no rotation property. */
+		*orientation = DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
+		return 0;
+	}
+
+	if (ret < 0)
+		return ret;
+
+	if (rotation == 0)
+		*orientation = DRM_MODE_PANEL_ORIENTATION_NORMAL;
+	else if (rotation == 90)
+		*orientation = DRM_MODE_PANEL_ORIENTATION_RIGHT_UP;
+	else if (rotation == 180)
+		*orientation = DRM_MODE_PANEL_ORIENTATION_BOTTOM_UP;
+	else if (rotation == 270)
+		*orientation = DRM_MODE_PANEL_ORIENTATION_LEFT_UP;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+EXPORT_SYMBOL(of_drm_get_panel_orientation);
 #endif
 
 MODULE_AUTHOR("Thierry Reding <treding@nvidia.com>");
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 8c738c0e6e9f..3564952f1a4f 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -197,11 +197,18 @@ int drm_panel_detach(struct drm_panel *panel);
 
 #if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL)
 struct drm_panel *of_drm_find_panel(const struct device_node *np);
+int of_drm_get_panel_orientation(const struct device_node *np,
+				 enum drm_panel_orientation *orientation);
 #else
 static inline struct drm_panel *of_drm_find_panel(const struct device_node *np)
 {
 	return ERR_PTR(-ENODEV);
 }
+int of_drm_get_panel_orientation(const struct device_node *np,
+				 enum drm_panel_orientation *orientation)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif
-- 
2.22.0.410.gd8fdbe21b5-goog

