This patch adds the ability for userspace applications to provide damage
information to the underlying driver. This is useful in scenarios where the
underlying driver can perform transfer optimizations based on knowing
exactly which framebuffer areas that were updated. This functionality is
exposed by using a simple x,y,w,h bounding box structure. Userspace is
expected to perform its damage and then perform the ioctl. The underlying
driver is free to use this information as it sees fit including ignoring it
if it chooses to. An example use case will be provided in the case of
broadsheetfb.c where the damage information is aggregated for deferred use.

Signed-off-by: Jaya Kumar <redacted>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Krzysztof Helt <redacted>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: armbru@redhat.com
Cc: lethal@linux-sh.org
Cc: adaplas@gmail.com
Cc: linux-fbdev-devel@lists.sourceforge.net
---
 drivers/video/fbmem.c |   61 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fb.h    |   24 +++++++++++++++++++
 2 files changed, 85 insertions(+), 0 deletions(-)

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 756efeb..f95ec45 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c

@@ -1006,6 +1006,60 @@ fb_blank(struct fb_info *info, int blank)
  	return ret;
 }
 
+static int fb_alloc_damage(struct fb_damage **damagep, int len)
+{
+	struct fb_damage *damage;
+
+	damage = kzalloc(sizeof(struct fb_damage), GFP_KERNEL);
+	if (!damage)
+		return -ENOMEM;
+
+	damage->len = len;
+	damage->rects = kzalloc(sizeof(struct fb_damage_rect) * len,
+				GFP_KERNEL);
+	if (!damage->rects) {
+		kfree(damage);
+		return -ENOMEM;
+	}
+
+	*damagep = damage;
+	return 0;
+}
+
+static void fb_free_damage(struct fb_damage *damage)
+{
+	if (damage)
+		kfree(damage->rects);
+	kfree(damage);
+}
+
+static int fb_set_damage(struct fb_info *info, struct fb_damage_user *udamage)
+{
+	int ret = -EINVAL;
+	int size = udamage->len;
+	struct fb_damage *damage;
+
+	if (size > FB_DAMAGE_COUNT_MAX)
+		goto fail;
+
+	ret = fb_alloc_damage(&damage, size);
+	if (ret)
+		goto fail;
+
+	if (copy_from_user(damage->rects, udamage->rects,
+				sizeof(struct fb_damage_rect)*size)) {
+		ret = -EFAULT;
+		goto fail2;
+	}
+
+	if (info->fbops->fb_set_damage)
+		return info->fbops->fb_set_damage(info, damage);
+fail2:
+	fb_free_damage(damage);
+fail:
+	return ret;
+}
+
 static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
 			unsigned long arg)
 {

@@ -1015,6 +1069,7 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
 	struct fb_con2fbmap con2fb;
 	struct fb_cmap_user cmap;
 	struct fb_event event;
+	struct fb_damage_user udamage;
 	void __user *argp = (void __user *)arg;
 	long ret = 0;
 

@@ -1116,6 +1171,12 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd,
 		info->flags &= ~FBINFO_MISC_USEREVENT;
 		release_console_sem();
 		break;;
+	case FBIOPUT_DAMAGE:
+		if (copy_from_user(&udamage, argp, sizeof(udamage)))
+			ret = -EFAULT;
+		else
+			ret = fb_set_damage(info, &udamage);
+		break;
 	default:
 		if (fb->fb_ioctl == NULL)
 			ret = -ENOTTY;

diff --git a/include/linux/fb.h b/include/linux/fb.h
index 1ee63df..8ee5f6d 100644
--- a/include/linux/fb.h
+++ b/include/linux/fb.h

@@ -37,7 +37,10 @@ struct dentry;
 #define FBIOGET_HWCINFO         0x4616
 #define FBIOPUT_MODEINFO        0x4617
 #define FBIOGET_DISPINFO        0x4618
+/* to allow userspace to provide screen damage information to drivers */
+#define FBIOPUT_DAMAGE          0x4619
 
+#define FB_DAMAGE_COUNT_MAX	32	/* max number of damage rects */
 
 #define FB_TYPE_PACKED_PIXELS		0	/* Packed Pixels	*/
 #define FB_TYPE_PLANES			1	/* Non interleaved planes */

@@ -357,6 +360,24 @@ struct fb_image {
 	struct fb_cmap cmap;	/* color map info */
 };
 
+struct fb_damage_rect {
+	__u16 x;
+	__u16 y;
+	__u16 w;
+	__u16 h;
+};
+
+struct fb_damage {
+	struct list_head list;
+	__u32 len;		/* Number of entries */
+	struct fb_damage_rect *rects; /* array of damage rectangles */
+};
+
+struct fb_damage_user {
+	__u32 len;		/* Number of entries */
+	struct fb_damage_rect __user *rects; /* array of damage rectangles */
+};
+
 /*
  * hardware cursor control
  */

@@ -672,6 +693,9 @@ struct fb_ops {
 	/* get capability given var */
 	void (*fb_get_caps)(struct fb_info *info, struct fb_blit_caps *caps,
 			    struct fb_var_screeninfo *var);
+
+	/* provide damage information */
+	int (*fb_set_damage)(struct fb_info *info, struct fb_damage *damage);
 };
 
 #ifdef CONFIG_FB_TILEBLITTING