ALSA: Allocate larger pages in sgbuf

[linux-2.6-omap-h63xx.git] / sound / core / pcm_memory.c

diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index 859b1185e69a953f7e212953930c147a6f9d8a76..a6d42808828c7d87d233f61782e753c7e99ba646 100644 (file)
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -324,6 +324,32 @@ struct page *snd_pcm_sgbuf_ops_page(struct snd_pcm_substream *substream, unsigne
 
 EXPORT_SYMBOL(snd_pcm_sgbuf_ops_page);
 
+/*
+ * compute the max chunk size with continuous pages on sg-buffer
+ */
+unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream,
+                                         unsigned int ofs, unsigned int size)
+{
+       struct snd_sg_buf *sg = snd_pcm_substream_sgbuf(substream);
+       unsigned int start, end, pg;
+
+       start = ofs >> PAGE_SHIFT;
+       end = (ofs + size - 1) >> PAGE_SHIFT;
+       /* check page continuity */
+       pg = sg->table[start].addr >> PAGE_SHIFT;
+       for (;;) {
+               start++;
+               if (start > end)
+                       break;
+               pg++;
+               if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
+                       return (start << PAGE_SHIFT) - ofs;
+       }
+       /* ok, all on continuous pages */
+       return size;
+}
+EXPORT_SYMBOL(snd_pcm_sgbuf_get_chunk_size);
+
 /**
  * snd_pcm_lib_malloc_pages - allocate the DMA buffer
  * @substream: the substream to allocate the DMA buffer to