HID: uhid: implement write() on uhid devices

Similar to read() you can only write() a single event with one call to an
uhid device. To write multiple events use writev() which is supported by
uhid.

We currently always return -EOPNOTSUPP but other events will be added in
later patches.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 30 insertions, 1 deletions

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 93860826d629..31e8379cfd15 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -30,6 +30,7 @@
 struct uhid_device {
         struct mutex devlock;
         struct hid_device *hid;
+        struct uhid_event input_buf;
 
         wait_queue_head_t waitq;
         spinlock_t qlock;
@@ -156,7 +157,35 @@ try_again:
 static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
                                 size_t count, loff_t *ppos)
 {
-        return 0;
+        struct uhid_device *uhid = file->private_data;
+        int ret;
+        size_t len;
+
+        /* we need at least the "type" member of uhid_event */
+        if (count < sizeof(__u32))
+                return -EINVAL;
+
+        ret = mutex_lock_interruptible(&uhid->devlock);
+        if (ret)
+                return ret;
+
+        memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
+        len = min(count, sizeof(uhid->input_buf));
+        if (copy_from_user(&uhid->input_buf, buffer, len)) {
+                ret = -EFAULT;
+                goto unlock;
+        }
+
+        switch (uhid->input_buf.type) {
+        default:
+                ret = -EOPNOTSUPP;
+        }
+
+unlock:
+        mutex_unlock(&uhid->devlock);
+
+        /* return "count" not "len" to not confuse the caller */
+        return ret ? ret : count;
 }
 
 static unsigned int uhid_char_poll(struct file *file, poll_table *wait)