Input: uinput - add UI_GET_SYSNAME ioctl to retrieve the sysfs path

uinput is used in the xorg-integration-tests suite and in the wayland
test suite. These automated tests suites create many virtual input
devices and then hook something to read these newly created devices.

Currently, uinput does not provide the created input device, which means
that we rely on an heuristic to guess which input node was created.
The problem is that is heuristic is subjected to races between different
uinput devices or even with physical devices. Having a way to retrieve
the sysfs path allows us to find without any doubts the event node.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index d8ae08d12abf..856936247500 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -20,6 +20,8 @@
  * Author: Aristeu Sergio Rozanski Filho <aris@cathedrallabs.org>
  *
  * Changes/Revisions:
+ *      0.4     01/09/2014 (Benjamin Tissoires <benjamin.tissoires@redhat.com>)
+ *              - add UI_GET_SYSNAME ioctl
  *      0.3     09/04/2006 (Anssi Hannula <anssi.hannula@gmail.com>)
  *              - updated ff support for the changes in kernel interface
  *              - added MODULE_VERSION
@@ -670,6 +672,31 @@ static int uinput_ff_upload_from_user(const char __user *buffer,
         __ret;                                          \
 })
 
+static int uinput_str_to_user(void __user *dest, const char *str,
+                              unsigned int maxlen)
+{
+        char __user *p = dest;
+        int len, ret;
+
+        if (!str)
+                return -ENOENT;
+
+        if (maxlen == 0)
+                return -EINVAL;
+
+        len = strlen(str) + 1;
+        if (len > maxlen)
+                len = maxlen;
+
+        ret = copy_to_user(p, str, len);
+        if (ret)
+                return -EFAULT;
+
+        /* force terminating '\0' */
+        ret = put_user(0, p + len - 1);
+        return ret ? -EFAULT : len;
+}
+
 static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
                                  unsigned long arg, void __user *p)
 {
@@ -679,6 +706,8 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
         struct uinput_ff_erase  ff_erase;
         struct uinput_request   *req;
         char                    *phys;
+        const char              *name;
+        unsigned int            size;
 
         retval = mutex_lock_interruptible(&udev->mutex);
         if (retval)
@@ -831,6 +860,20 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
                         goto out;
         }
 
+        size = _IOC_SIZE(cmd);
+
+        /* Now check variable-length commands */
+        switch (cmd & ~IOCSIZE_MASK) {
+        case UI_GET_SYSNAME(0):
+                if (udev->state != UIST_CREATED) {
+                        retval = -ENOENT;
+                        goto out;
+                }
+                name = dev_name(&udev->dev->dev);
+                retval = uinput_str_to_user(p, name, size);
+                goto out;
+        }
+
         retval = -EINVAL;
  out:
         mutex_unlock(&udev->mutex);