usb: gadget/uvc: Add support for 'get_unmapped_area' for MMUless architectures

This patch adds the support for 'get_unmapped_area' in UVC gadget
which is called when the 'mmap' system call is executed on MMUless
architectures.

Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
diff --git a/drivers/usb/gadget/uvc_queue.c b/drivers/usb/gadget/uvc_queue.c
index 3139795..7ce27e3 100644
--- a/drivers/usb/gadget/uvc_queue.c
+++ b/drivers/usb/gadget/uvc_queue.c
@@ -232,6 +232,24 @@
 	return ret;
 }
 
+#ifndef CONFIG_MMU
+/*
+ * Get unmapped area.
+ *
+ * NO-MMU arch need this function to make mmap() work correctly.
+ */
+static unsigned long uvc_queue_get_unmapped_area(struct uvc_video_queue *queue,
+		unsigned long pgoff)
+{
+	unsigned long ret;
+
+	mutex_lock(&queue->mutex);
+	ret = vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
+	mutex_unlock(&queue->mutex);
+	return ret;
+}
+#endif
+
 /*
  * Cancel the video buffers queue.
  *