HID: uhid: allow feeding input data into uhid devices

This adds a new event type UHID_INPUT which allows user-space to feed raw
HID reports into the HID subsystem. We copy the data into kernel memory
and directly feed it into the HID core.

There is no error handling of the events couldn't be parsed so user-space
should consider all events successfull unless read() returns an error.
Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/uhid.c

@@ -210,6 +210,17 @@ static int uhid_dev_destroy(struct uhid_device *uhid)
 	return 0;
 }
 
+static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
+{
+	if (!uhid->running)
+		return -EINVAL;
+
+	hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
+			 min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
+
+	return 0;
+}
+
 static int uhid_char_open(struct inode *inode, struct file *file)
 {
 	struct uhid_device *uhid;
@@ -321,6 +332,9 @@ static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
 	case UHID_DESTROY:
 		ret = uhid_dev_destroy(uhid);
 		break;
+	case UHID_INPUT:
+		ret = uhid_dev_input(uhid, &uhid->input_buf);
+		break;
 	default:
 		ret = -EOPNOTSUPP;
 	}

include/linux/uhid.h

@@ -25,6 +25,7 @@
 enum uhid_event_type {
 	UHID_CREATE,
 	UHID_DESTROY,
+	UHID_INPUT,
 };
 
 struct uhid_create_req {
@@ -41,11 +42,19 @@ struct uhid_create_req {
 	__u32 country;
 } __attribute__((__packed__));
 
+#define UHID_DATA_MAX 4096
+
+struct uhid_input_req {
+	__u8 data[UHID_DATA_MAX];
+	__u16 size;
+} __attribute__((__packed__));
+
 struct uhid_event {
 	__u32 type;
 
 	union {
 		struct uhid_create_req create;
+		struct uhid_input_req input;
 	} u;
 } __attribute__((__packed__));