Input: Add EVIOC mechanism for MT slots

This patch adds the ability to extract MT slot data via a new ioctl,
EVIOCGMTSLOTS. The function returns an array of slot values for the
specified ABS_MT event type.

Example of user space usage:

struct { unsigned code; int values[64]; } req;
req.code = ABS_MT_POSITION_X;
if (ioctl(fd, EVIOCGMTSLOTS(sizeof(req)), &req) < 0)
	return -1;
for (i = 0; i < 64; i++)
	printf("slot %d: %d\n", i, req.values[i]);

Reviewed-by: Chase Douglas <chase.douglas@canonical.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 76457d5..e4cad16 100644 (file)
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -20,7 +20,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/init.h>
-#include <linux/input.h>
+#include <linux/input/mt.h>
 #include <linux/major.h>
 #include <linux/device.h>
 #include "input-compat.h"
@@ -623,6 +623,28 @@ static int evdev_handle_set_keycode_v2(struct input_dev *dev, void __user *p)
        return input_set_keycode(dev, &ke);
 }
 
+static int evdev_handle_mt_request(struct input_dev *dev,
+                                  unsigned int size,
+                                  int __user *ip)
+{
+       const struct input_mt_slot *mt = dev->mt;
+       unsigned int code;
+       int max_slots;
+       int i;
+
+       if (get_user(code, &ip[0]))
+               return -EFAULT;
+       if (!input_is_mt_value(code))
+               return -EINVAL;
+
+       max_slots = (size - sizeof(__u32)) / sizeof(__s32);
+       for (i = 0; i < dev->mtsize && i < max_slots; i++)
+               if (put_user(input_mt_get_value(&mt[i], code), &ip[1 + i]))
+                       return -EFAULT;
+
+       return 0;
+}
+
 static long evdev_do_ioctl(struct file *file, unsigned int cmd,
                           void __user *p, int compat_mode)
 {
@@ -708,6 +730,9 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
                return bits_to_user(dev->propbit, INPUT_PROP_MAX,
                                    size, p, compat_mode);
 
+       case EVIOCGMTSLOTS(0):
+               return evdev_handle_mt_request(dev, size, ip);
+
        case EVIOCGKEY(0):
                return bits_to_user(dev->key, KEY_MAX, size, p, compat_mode);
 

diff --git a/include/linux/input.h b/include/linux/input.h
index 3862e32..af26443 100644 (file)
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -114,6 +114,31 @@ struct input_keymap_entry {
 #define EVIOCGUNIQ(len)                _IOC(_IOC_READ, 'E', 0x08, len)         /* get unique identifier */
 #define EVIOCGPROP(len)                _IOC(_IOC_READ, 'E', 0x09, len)         /* get device properties */
 
+/**
+ * EVIOCGMTSLOTS(len) - get MT slot values
+ *
+ * The ioctl buffer argument should be binary equivalent to
+ *
+ * struct input_mt_request_layout {
+ *     __u32 code;
+ *     __s32 values[num_slots];
+ * };
+ *
+ * where num_slots is the (arbitrary) number of MT slots to extract.
+ *
+ * The ioctl size argument (len) is the size of the buffer, which
+ * should satisfy len = (num_slots + 1) * sizeof(__s32).  If len is
+ * too small to fit all available slots, the first num_slots are
+ * returned.
+ *
+ * Before the call, code is set to the wanted ABS_MT event type. On
+ * return, values[] is filled with the slot values for the specified
+ * ABS_MT code.
+ *
+ * If the request code is not an ABS_MT value, -EINVAL is returned.
+ */
+#define EVIOCGMTSLOTS(len)     _IOC(_IOC_READ, 'E', 0x0a, len)
+
 #define EVIOCGKEY(len)         _IOC(_IOC_READ, 'E', 0x18, len)         /* get global key state */
 #define EVIOCGLED(len)         _IOC(_IOC_READ, 'E', 0x19, len)         /* get all LEDs */
 #define EVIOCGSND(len)         _IOC(_IOC_READ, 'E', 0x1a, len)         /* get all sounds status */