Input: synaptics - add support for reporting x/y resolution

Synaptics uses anisotropic coordinate system.  On some wide touchpads
vertical resolution can be twice as high as horizontal which causes
unequal sensitivity on x/y directions.  Add support for reading the
resolution with EVIOCGABS ioctl.

Signed-off-by: Tero Saarni <tero.saarni@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index c238116..114efd8 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -626,8 +626,11 @@
 				abs.maximum = dev->absmax[t];
 				abs.fuzz = dev->absfuzz[t];
 				abs.flat = dev->absflat[t];
+				abs.resolution = dev->absres[t];
 
-				if (copy_to_user(p, &abs, sizeof(struct input_absinfo)))
+				if (copy_to_user(p, &abs, min_t(size_t,
+								_IOC_SIZE(cmd),
+								sizeof(struct input_absinfo))))
 					return -EFAULT;
 
 				return 0;
@@ -654,8 +657,9 @@
 
 				t = _IOC_NR(cmd) & ABS_MAX;
 
-				if (copy_from_user(&abs, p,
-						sizeof(struct input_absinfo)))
+				if (copy_from_user(&abs, p, min_t(size_t,
+								  _IOC_SIZE(cmd),
+								  sizeof(struct input_absinfo))))
 					return -EFAULT;
 
 				/*
@@ -670,6 +674,8 @@
 				dev->absmax[t] = abs.maximum;
 				dev->absfuzz[t] = abs.fuzz;
 				dev->absflat[t] = abs.flat;
+				dev->absres[t] = _IOC_SIZE(cmd) < sizeof(struct input_absinfo) ?
+							0 : abs.resolution;
 
 				spin_unlock_irq(&dev->event_lock);