fbcon: Add fbcon_rotate_hint to struct fb_info

On some hardware the LCD panel is not mounted upright in the casing,
but upside-down or rotated 90 degrees. In this case we want the console
to automatically be rotated to compensate.

The fbdev-driver may know about the need to rotate. Add a new
fbcon_rotate_hint field to struct fb_info, which gets initialized to -1.
If the fbdev-driver knows that some sort of rotation is necessary then
it can set this field to a FB_ROTATE_* value to tell the fbcon console
driver to rotate the console.
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171125193553.23986-2-hdegoede@redhat.com

drivers/video/fbdev/core/fbcon.c

@@ -964,10 +964,13 @@ static const char *fbcon_startup(void)
 	ops->cur_blink_jiffies = HZ / 5;
 	ops->info = info;
 	info->fbcon_par = ops;
-	if (initial_rotation != -1)
-		p->con_rotate = initial_rotation;
-	else
+
+	p->con_rotate = initial_rotation;
+	if (p->con_rotate == -1)
+		p->con_rotate = info->fbcon_rotate_hint;
+	if (p->con_rotate == -1)
 		p->con_rotate = fbcon_platform_get_rotate(info);
+
 	set_blitting_type(vc, info);
 
 	if (info->fix.type != FB_TYPE_TEXT) {
@@ -1104,10 +1107,13 @@ static void fbcon_init(struct vc_data *vc, int init)
 
 	ops = info->fbcon_par;
 	ops->cur_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);
-	if (initial_rotation != -1)
-		p->con_rotate = initial_rotation;
-	else
+
+	p->con_rotate = initial_rotation;
+	if (p->con_rotate == -1)
+		p->con_rotate = info->fbcon_rotate_hint;
+	if (p->con_rotate == -1)
 		p->con_rotate = fbcon_platform_get_rotate(info);
+
 	set_blitting_type(vc, info);
 
 	cols = vc->vc_cols;

drivers/video/fbdev/core/fbsysfs.c

@@ -58,6 +58,7 @@ struct fb_info *framebuffer_alloc(size_t size, struct device *dev)
 		info->par = p + fb_info_size;
 
 	info->device = dev;
+	info->fbcon_rotate_hint = -1;
 
 #ifdef CONFIG_FB_BACKLIGHT
 	mutex_init(&info->bl_curve_mutex);

include/linux/fb.h

@@ -465,6 +465,11 @@ struct fb_info {
 	atomic_t count;
 	int node;
 	int flags;
+	/*
+	 * -1 by default, set to a FB_ROTATE_* value by the driver, if it knows
+	 * a lcd is not mounted upright and fbcon should rotate to compensate.
+	 */
+	int fbcon_rotate_hint;
 	struct mutex lock;		/* Lock for open/release/ioctl funcs */
 	struct mutex mm_lock;		/* Lock for fb_mmap and smem_* fields */
 	struct fb_var_screeninfo var;	/* Current var */