media: v4l2-mem2mem: add v4l2_m2m_get_unmapped_area for no-mmu platform

For platforms without MMU the m2m provides a helper method
v4l2_m2m_get_unmapped_area(), The mmap() routines will call
this to get a proposed address for the mapping.

More detailed information about get_unmapped_area can be found in
Documentation/nommu-mmap.txt
Signed-off-by: Dillon Min <dillon.minfei@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/v4l2-core/v4l2-mem2mem.c

@@ -966,6 +966,27 @@ int v4l2_m2m_mmap(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 }
 EXPORT_SYMBOL(v4l2_m2m_mmap);
 
+#ifndef CONFIG_MMU
+unsigned long v4l2_m2m_get_unmapped_area(struct file *file, unsigned long addr,
+					 unsigned long len, unsigned long pgoff,
+					 unsigned long flags)
+{
+	struct v4l2_fh *fh = file->private_data;
+	unsigned long offset = pgoff << PAGE_SHIFT;
+	struct vb2_queue *vq;
+
+	if (offset < DST_QUEUE_OFF_BASE) {
+		vq = v4l2_m2m_get_src_vq(fh->m2m_ctx);
+	} else {
+		vq = v4l2_m2m_get_dst_vq(fh->m2m_ctx);
+		pgoff -= (DST_QUEUE_OFF_BASE >> PAGE_SHIFT);
+	}
+
+	return vb2_get_unmapped_area(vq, addr, len, pgoff, flags);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_get_unmapped_area);
+#endif
+
 #if defined(CONFIG_MEDIA_CONTROLLER)
 void v4l2_m2m_unregister_media_controller(struct v4l2_m2m_dev *m2m_dev)
 {

include/media/v4l2-mem2mem.h

@@ -495,6 +495,11 @@ __poll_t v4l2_m2m_poll(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 int v4l2_m2m_mmap(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 		  struct vm_area_struct *vma);
 
+#ifndef CONFIG_MMU
+unsigned long v4l2_m2m_get_unmapped_area(struct file *file, unsigned long addr,
+					 unsigned long len, unsigned long pgoff,
+					 unsigned long flags);
+#endif
 /**
  * v4l2_m2m_init() - initialize per-driver m2m data
  *