+ snd_card_saa7134_t *saa7134 = snd_pcm_substream_chip(substream);
+ struct saa7134_dev *dev;
+ unsigned int period_size, periods;
+ int err;
+
+ period_size = params_period_bytes(hw_params);
+ periods = params_periods(hw_params);
+
+ snd_assert(period_size >= 0x100 && period_size <= 0x10000,
+ return -EINVAL);
+ snd_assert(periods >= 2, return -EINVAL);
+ snd_assert(period_size * periods <= 1024 * 1024, return -EINVAL);
+
+ dev = saa7134->dev;
+
+ if (dev->dmasound.blocks == periods &&
+ dev->dmasound.blksize == period_size)
+ return 0;
+
+ /* release the old buffer */
+ if (substream->runtime->dma_area) {
+ saa7134_pgtable_free(dev->pci, &dev->dmasound.pt);
+ videobuf_dma_pci_unmap(dev->pci, &dev->dmasound.dma);
+ dsp_buffer_free(dev);
+ substream->runtime->dma_area = NULL;
+ }
+ dev->dmasound.blocks = periods;
+ dev->dmasound.blksize = period_size;
+ dev->dmasound.bufsize = period_size * periods;
+
+ err = dsp_buffer_init(dev);
+ if (0 != err) {
+ dev->dmasound.blocks = 0;
+ dev->dmasound.blksize = 0;
+ dev->dmasound.bufsize = 0;
+ return err;
+ }
+
+ if (0 != (err = videobuf_dma_pci_map(dev->pci, &dev->dmasound.dma))) {
+ dsp_buffer_free(dev);
+ return err;
+ }
+ if (0 != (err = saa7134_pgtable_alloc(dev->pci,&dev->dmasound.pt))) {
+ videobuf_dma_pci_unmap(dev->pci, &dev->dmasound.dma);
+ dsp_buffer_free(dev);
+ return err;
+ }
+ if (0 != (err = saa7134_pgtable_build(dev->pci,&dev->dmasound.pt,
+ dev->dmasound.dma.sglist,
+ dev->dmasound.dma.sglen,
+ 0))) {
+ saa7134_pgtable_free(dev->pci, &dev->dmasound.pt);
+ videobuf_dma_pci_unmap(dev->pci, &dev->dmasound.dma);
+ dsp_buffer_free(dev);
+ return err;
+ }
+
+ /* I should be able to use runtime->dma_addr in the control
+ byte, but it doesn't work. So I allocate the DMA using the
+ V4L functions, and force ALSA to use that as the DMA area */
+
+ substream->runtime->dma_area = dev->dmasound.dma.vmalloc;
+
+ return 1;