[RFC PATCH 1/2] drm/panel: add support for simple-panel description definition using DT

[Boris BREZILLON]

Currently, the only way to add new panel descriptions to the simple panel
driver is to add new entries in the platform_of_match table.

Add support for panel description retrieval from the DT.

Signed-off-by: Boris BREZILLON <boris.brezillon at free-electrons.com>
---
 drivers/gpu/drm/panel/Kconfig        |  1 +
 drivers/gpu/drm/panel/panel-simple.c | 70 ++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index 4ec874d..4fe3d48 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -1,6 +1,7 @@
 config DRM_PANEL
 	bool
 	depends on DRM
+	select VIDEOMODE_HELPERS
 	help
 	  Panel registration and lookup framework.
 
diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 309f29e..fcf648d 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -33,6 +33,10 @@
 #include <drm/drm_mipi_dsi.h>
 #include <drm/drm_panel.h>
 
+#include <video/display_timing.h>
+#include <video/of_display_timing.h>
+#include <video/videomode.h>
+
 struct panel_desc {
 	const struct drm_display_mode *modes;
 	unsigned int num_modes;
@@ -168,6 +172,61 @@ static const struct drm_panel_funcs panel_simple_funcs = {
 	.get_modes = panel_simple_get_modes,
 };
 
+static struct panel_desc *of_panel_desc_init(struct device *dev)
+{
+	struct display_timings *timings;
+	struct panel_desc *desc;
+	u32 width, height;
+	int err;
+	int i;
+
+	err = of_property_read_u32(dev->of_node, "width", &width);
+	if (err)
+		return ERR_PTR(err);
+
+	err = of_property_read_u32(dev->of_node, "height", &height);
+	if (err)
+		return ERR_PTR(err);
+
+	desc = devm_kzalloc(dev, sizeof(*desc), GFP_KERNEL);
+	if (!desc)
+		return ERR_PTR(-ENOMEM);
+
+	timings = of_get_display_timings(dev->of_node);
+	if (timings) {
+		struct drm_display_mode *modes =
+				devm_kzalloc(dev,
+					     timings->num_timings *
+					     sizeof(*desc->modes),
+					     GFP_KERNEL);
+
+		if (!modes)
+			return ERR_PTR(-ENOMEM);
+
+		for (i = 0; i < timings->num_timings; i++) {
+			struct videomode vm;
+
+			if (videomode_from_timings(timings, &vm, i))
+				break;
+
+			drm_display_mode_from_videomode(&vm, modes + i);
+
+			modes[i].type = DRM_MODE_TYPE_DRIVER;
+
+			if (timings->native_mode == i)
+				modes[i].type |= DRM_MODE_TYPE_PREFERRED;
+			desc->num_modes++;
+		}
+
+		kfree(timings);
+	}
+
+	desc->size.width = width;
+	desc->size.height = height;
+
+	return desc;
+}
+
 static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 {
 	struct device_node *backlight, *ddc;
@@ -178,6 +237,17 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	if (!panel)
 		return -ENOMEM;
 
+	if (!desc) {
+		desc = of_panel_desc_init(dev);
+		/*
+		 * Do not fail on DT panel desc retrieval error because
+		 * some systems do not need a panel description to work
+		 * properly.
+		 */
+		if (IS_ERR(desc))
+			desc = NULL;
+	}
+
 	panel->enabled = false;
 	panel->desc = desc;
 
-- 
1.8.3.2