staging: comedi: gsc_hpdi: tidy up setup_dma_descriptors()

For aesthetics, rename this function so it has namespace associated
with the driver and move it so that it is not in the middle of the
async command support code.

Tidy up the function a bit.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/gsc_hpdi.c

@@ -218,57 +218,6 @@ static void disable_plx_interrupts(struct comedi_device *dev)
 	writel(0, devpriv->plx9080_iobase + PLX_INTRCS_REG);
 }
 
-/* setup dma descriptors so a link completes every 'transfer_size' bytes */
-static int setup_dma_descriptors(struct comedi_device *dev,
-				 unsigned int transfer_size)
-{
-	struct hpdi_private *devpriv = dev->private;
-	unsigned int buffer_index, buffer_offset;
-	uint32_t next_bits = PLX_DESC_IN_PCI_BIT | PLX_INTR_TERM_COUNT |
-	    PLX_XFER_LOCAL_TO_PCI;
-	unsigned int i;
-
-	if (transfer_size > DMA_BUFFER_SIZE)
-		transfer_size = DMA_BUFFER_SIZE;
-	transfer_size -= transfer_size % sizeof(uint32_t);
-	if (transfer_size == 0)
-		return -1;
-
-	buffer_offset = 0;
-	buffer_index = 0;
-	for (i = 0; i < NUM_DMA_DESCRIPTORS &&
-	     buffer_index < NUM_DMA_BUFFERS; i++) {
-		devpriv->dma_desc[i].pci_start_addr =
-		    cpu_to_le32(devpriv->dio_buffer_phys_addr[buffer_index] +
-				buffer_offset);
-		devpriv->dma_desc[i].local_start_addr = cpu_to_le32(FIFO_REG);
-		devpriv->dma_desc[i].transfer_size =
-		    cpu_to_le32(transfer_size);
-		devpriv->dma_desc[i].next =
-		    cpu_to_le32((devpriv->dma_desc_phys_addr + (i +
-								  1) *
-				 sizeof(devpriv->dma_desc[0])) | next_bits);
-
-		devpriv->desc_dio_buffer[i] =
-		    devpriv->dio_buffer[buffer_index] +
-		    (buffer_offset / sizeof(uint32_t));
-
-		buffer_offset += transfer_size;
-		if (transfer_size + buffer_offset > DMA_BUFFER_SIZE) {
-			buffer_offset = 0;
-			buffer_index++;
-		}
-	}
-	devpriv->num_dma_descriptors = i;
-	/*  fix last descriptor to point back to first */
-	devpriv->dma_desc[i - 1].next =
-	    cpu_to_le32(devpriv->dma_desc_phys_addr | next_bits);
-
-	devpriv->block_size = transfer_size;
-
-	return transfer_size;
-}
-
 static int di_cmd_test(struct comedi_device *dev, struct comedi_subdevice *s,
 		       struct comedi_cmd *cmd)
 {
@@ -558,6 +507,50 @@ static int hpdi_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
 	return 0;
 }
 
+/* setup dma descriptors so a link completes every 'len' bytes */
+static int gsc_hpdi_setup_dma_descriptors(struct comedi_device *dev,
+					  unsigned int len)
+{
+	struct hpdi_private *devpriv = dev->private;
+	dma_addr_t phys_addr = devpriv->dma_desc_phys_addr;
+	uint32_t next_bits = PLX_DESC_IN_PCI_BIT | PLX_INTR_TERM_COUNT |
+			     PLX_XFER_LOCAL_TO_PCI;
+	unsigned int offset = 0;
+	unsigned int idx = 0;
+	unsigned int i;
+
+	if (len > DMA_BUFFER_SIZE)
+		len = DMA_BUFFER_SIZE;
+	len -= len % sizeof(uint32_t);
+	if (len == 0)
+		return -EINVAL;
+
+	for (i = 0; i < NUM_DMA_DESCRIPTORS && idx < NUM_DMA_BUFFERS; i++) {
+		devpriv->dma_desc[i].pci_start_addr =
+		    cpu_to_le32(devpriv->dio_buffer_phys_addr[idx] + offset);
+		devpriv->dma_desc[i].local_start_addr = cpu_to_le32(FIFO_REG);
+		devpriv->dma_desc[i].transfer_size = cpu_to_le32(len);
+		devpriv->dma_desc[i].next = cpu_to_le32((phys_addr +
+			(i + 1) * sizeof(devpriv->dma_desc[0])) | next_bits);
+
+		devpriv->desc_dio_buffer[i] = devpriv->dio_buffer[idx] +
+					      (offset / sizeof(uint32_t));
+
+		offset += len;
+		if (len + offset > DMA_BUFFER_SIZE) {
+			offset = 0;
+			idx++;
+		}
+	}
+	devpriv->num_dma_descriptors = i;
+	/* fix last descriptor to point back to first */
+	devpriv->dma_desc[i - 1].next = cpu_to_le32(phys_addr | next_bits);
+
+	devpriv->block_size = len;
+
+	return len;
+}
+
 static int gsc_hpdi_dio_insn_config(struct comedi_device *dev,
 				    struct comedi_subdevice *s,
 				    struct comedi_insn *insn,
@@ -567,7 +560,7 @@ static int gsc_hpdi_dio_insn_config(struct comedi_device *dev,
 
 	switch (data[0]) {
 	case INSN_CONFIG_BLOCK_SIZE:
-		ret = setup_dma_descriptors(dev, data[1]);
+		ret = gsc_hpdi_setup_dma_descriptors(dev, data[1]);
 		if (ret)
 			return ret;
 
@@ -728,7 +721,7 @@ static int hpdi_auto_attach(struct comedi_device *dev,
 		return -EIO;
 	}
 
-	retval = setup_dma_descriptors(dev, 0x1000);
+	retval = gsc_hpdi_setup_dma_descriptors(dev, 0x1000);
 	if (retval < 0)
 		return retval;