[media] V4L: soc_camera: allow reading from video device if supported

Try reading on video device. If the camera bus driver supports reading
we can try it and return the result. Also add a debug line.
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/soc_camera/soc_camera.c

@@ -645,11 +645,17 @@ static ssize_t soc_camera_read(struct file *file, char __user *buf,
 			       size_t count, loff_t *ppos)
 {
 	struct soc_camera_device *icd = file->private_data;
-	int err = -EINVAL;
+	struct soc_camera_host *ici = to_soc_camera_host(icd->parent);
+
+	dev_dbg(icd->pdev, "read called, buf %p\n", buf);
+
+	if (ici->ops->init_videobuf2 && icd->vb2_vidq.io_modes & VB2_READ)
+		return vb2_read(&icd->vb2_vidq, buf, count, ppos,
+				file->f_flags & O_NONBLOCK);
 
 	dev_err(icd->pdev, "camera device read not implemented\n");
 
-	return err;
+	return -EINVAL;
 }
 
 static int soc_camera_mmap(struct file *file, struct vm_area_struct *vma)