[RFC PATCH 3/6] fbdev: honour the device tree boot logo placement properties

[Max Pedraza]

A logo supplied by the device tree describes a specific product, so where
it lands on the panel matters in a way it does not for the built-in Tux.
Honour the optional "logo-position", "logo-offset", "logo-centered" and
"logo-rotation" properties of the "linux,boot-logo-clut224" node.

The rotation is folded into the rotate argument at the entry points, so
fb_prepare_logo() reserves the right amount of space and fb_do_show_logo()
tiles in the same direction the image was rotated in.

Placement is applied after fb_rotate_logo(), since a rotation swaps the
image width and height and centring needs the final dimensions.

fb_prepare_logo() has to grow its reservation to cover wherever the logo
ends up, the way fb_center_logo already does: fbcon only leaves the first
n rows alone, so a logo placed further down is drawn and then immediately
cleared by the console.

"logo-centered" is deliberately close to the existing fb_center_logo, but
it is per device tree rather than per fbcon command line, and it composes
with "logo-offset" so that a logo can be centred and then nudged. That
combination is what panels with a partially visible area need, where the
usable region is not the centre of the mode.

Signed-off-by: Max Pedraza <maximpedraza@xxxxxxxxx>
---
 drivers/video/fbdev/core/fb_logo.c | 174 +++++++++++++++++++++++++++++
 1 file changed, 174 insertions(+)

diff --git a/drivers/video/fbdev/core/fb_logo.c b/drivers/video/fbdev/core/fb_logo.c
index 0bab8352b..bfc1b72ce 100644
--- a/drivers/video/fbdev/core/fb_logo.c
+++ b/drivers/video/fbdev/core/fb_logo.c
@@ -2,12 +2,178 @@
 
 #include <linux/fb.h>
 #include <linux/linux_logo.h>
+#include <linux/of.h>
 
 #include "fb_internal.h"
 
 bool fb_center_logo __read_mostly;
 int fb_logo_count __read_mostly = -1;
 
+#ifdef CONFIG_LOGO_DT_CLUT224
+
+/*
+ * Placement of a logo supplied by the device tree. The image itself is parsed
+ * by drivers/video/logo/logo.c, here we only care about where it goes.
+ */
+struct fb_logo_dt_placement {
+	bool valid;
+	bool centered;
+	bool has_position;
+	int rotation;		/* FB_ROTATE_*, or -1 when unspecified */
+	u32 x, y;
+	s32 offset_x, offset_y;
+};
+
+static struct fb_logo_dt_placement fb_logo_dt;
+
+static int fb_logo_dt_parse_rotation(const char *rotation)
+{
+	if (!strcmp(rotation, "none"))
+		return FB_ROTATE_UR;
+	if (!strcmp(rotation, "cw"))
+		return FB_ROTATE_CW;
+	if (!strcmp(rotation, "ud"))
+		return FB_ROTATE_UD;
+	if (!strcmp(rotation, "ccw"))
+		return FB_ROTATE_CCW;
+
+	return -EINVAL;
+}
+
+static void fb_logo_dt_read(void)
+{
+	struct fb_logo_dt_placement *p = &fb_logo_dt;
+	static bool read_done;
+	struct device_node *np;
+	const char *rotation;
+	u32 val[2];
+	int rot;
+
+	if (read_done)
+		return;
+
+	read_done = true;
+
+	np = of_find_compatible_node(NULL, NULL, "linux,boot-logo-clut224");
+	if (!np)
+		return;
+
+	if (!of_device_is_available(np))
+		goto out;
+
+	p->valid = true;
+	p->rotation = -1;
+	p->centered = of_property_read_bool(np, "logo-centered");
+
+	if (!of_property_read_u32_array(np, "logo-position", val, 2)) {
+		p->has_position = true;
+		p->x = val[0];
+		p->y = val[1];
+	}
+
+	if (!of_property_read_u32_array(np, "logo-offset", val, 2)) {
+		p->offset_x = (s32)val[0];
+		p->offset_y = (s32)val[1];
+	}
+
+	if (!of_property_read_string(np, "logo-rotation", &rotation)) {
+		rot = fb_logo_dt_parse_rotation(rotation);
+		if (rot < 0)
+			pr_warn("fb: %pOF: unknown logo-rotation \"%s\"\n",
+				np, rotation);
+		else
+			p->rotation = rot;
+	}
+
+out:
+	of_node_put(np);
+}
+
+static int fb_logo_dt_rotation(int rotate)
+{
+	fb_logo_dt_read();
+
+	if (fb_logo_dt.valid && fb_logo_dt.rotation >= 0)
+		return fb_logo_dt.rotation;
+
+	return rotate;
+}
+
+/* Top edge of the logo, in the coordinate space the caller works in */
+static int fb_logo_dt_top(unsigned int yres, unsigned int logo_height)
+{
+	struct fb_logo_dt_placement *p = &fb_logo_dt;
+	int top;
+
+	if (p->centered)
+		top = ((int)yres - (int)logo_height) / 2;
+	else if (p->has_position)
+		top = p->y;
+	else
+		top = 0;
+
+	return max(top + p->offset_y, 0);
+}
+
+static void fb_logo_dt_place(struct fb_info *info, struct fb_image *image)
+{
+	struct fb_logo_dt_placement *p = &fb_logo_dt;
+	int dx;
+
+	fb_logo_dt_read();
+
+	if (!p->valid)
+		return;
+
+	if (p->centered)
+		dx = ((int)info->var.xres - (int)image->width) / 2;
+	else if (p->has_position)
+		dx = p->x;
+	else
+		dx = image->dx;
+
+	image->dx = max(dx + p->offset_x, 0);
+	image->dy = fb_logo_dt_top(info->var.yres, image->height);
+}
+
+/*
+ * fbcon only leaves the first @height rows of the screen alone, so a logo
+ * placed further down would be drawn and then immediately cleared. Grow the
+ * reservation to cover wherever the logo actually ends up, the same way
+ * fb_center_logo does.
+ */
+static int fb_logo_dt_reserve(unsigned int yres, unsigned int logo_height,
+			      int height)
+{
+	fb_logo_dt_read();
+
+	if (!fb_logo_dt.valid)
+		return height;
+
+	return max(height, fb_logo_dt_top(yres, logo_height) +
+			   (int)logo_height);
+}
+
+#else /* !CONFIG_LOGO_DT_CLUT224 */
+
+static inline int fb_logo_dt_rotation(int rotate)
+{
+	return rotate;
+}
+
+static inline void fb_logo_dt_place(struct fb_info *info,
+				    struct fb_image *image)
+{
+}
+
+static inline int fb_logo_dt_reserve(unsigned int yres,
+				     unsigned int logo_height, int height)
+{
+	return height;
+}
+
+#endif /* CONFIG_LOGO_DT_CLUT224 */
+
 static inline unsigned int safe_shift(unsigned int d, int n)
 {
 	return n < 0 ? d >> -n : d << n;
@@ -350,6 +516,9 @@ static int fb_show_logo_line(struct fb_info *info, int rotate,
 			fb_rotate_logo(info, logo_rotate, &image, rotate);
 	}
 
+	/* Done last, image dimensions are only final after the rotation */
+	fb_logo_dt_place(info, &image);
+
 	fb_do_show_logo(info, &image, rotate, n);
 
 	kfree(palette);
@@ -423,6 +592,8 @@ int fb_prepare_logo(struct fb_info *info, int rotate)
 
 	memset(&fb_logo, 0, sizeof(struct logo_data));
 
+	rotate = fb_logo_dt_rotation(rotate);
+
 	if (info->flags & FBINFO_MISC_TILEBLITTING ||
 	    info->fbops->owner || !fb_logo_count)
 		return 0;
@@ -483,6 +654,7 @@ int fb_prepare_logo(struct fb_info *info, int rotate)
 	height = fb_logo.logo->height;
 	if (fb_center_logo)
 		height += (yres - fb_logo.logo->height) / 2;
+	height = fb_logo_dt_reserve(yres, fb_logo.logo->height, height);
 #ifdef CONFIG_FB_LOGO_EXTRA
 	height = fb_prepare_extra_logos(info, height, yres);
 #endif
@@ -498,6 +670,8 @@ int fb_show_logo(struct fb_info *info, int rotate)
 	if (!fb_logo_count)
 		return 0;
 
+	rotate = fb_logo_dt_rotation(rotate);
+
 	count = fb_logo_count < 0 ? num_online_cpus() : fb_logo_count;
 	y = fb_show_logo_line(info, rotate, fb_logo.logo, 0, count);
 #ifdef CONFIG_FB_LOGO_EXTRA
-- 
2.39.5