diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 8db8963..40c5a6f 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -996,7 +996,8 @@
 
 struct page *snd_pcm_sgbuf_ops_page(struct snd_pcm_substream *substream,
 				    unsigned long offset);
-
+unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream,
+					  unsigned int ofs, unsigned int size);
 
 /* handle mmap counter - PCM mmap callback should handle this counter properly */
 static inline void snd_pcm_mmap_data_open(struct vm_area_struct *area)