staging: comedi: dt282x: introduce dt282x_alloc_dma()

The IRA and DMA are optional with this driver but both are required to
support async commands. Introduce a helper function to request the IRQ
and DMA channel and allocate the buffers. Don't fail the driver attach
if the user passed an invalid IRQ or DMA channel or they cannot be
requested.
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/dt282x.c

@@ -1053,26 +1053,49 @@ static const struct comedi_lrange *opt_ai_range_lkup(int ispgl, int x)
 	return ai_range_table[x];
 }
 
-static int dt282x_grab_dma(struct comedi_device *dev, int dma1, int dma2)
+static int dt282x_alloc_dma(struct comedi_device *dev,
+			    struct comedi_devconfig *it)
 {
 	struct dt282x_private *devpriv = dev->private;
-	int ret;
+	unsigned int irq_num = it->options[1];
+	unsigned int dma_chan[2];
+	int i;
 
-	ret = request_dma(dma1, "dt282x A");
-	if (ret)
-		return -EBUSY;
-	devpriv->dma[0].chan = dma1;
+	if (it->options[2] < it->options[3]) {
+		dma_chan[0] = it->options[2];
+		dma_chan[1] = it->options[3];
+	} else {
+		dma_chan[0] = it->options[3];
+		dma_chan[1] = it->options[2];
+	}
 
-	ret = request_dma(dma2, "dt282x B");
-	if (ret)
-		return -EBUSY;
-	devpriv->dma[1].chan = dma2;
+	if (!irq_num || dma_chan[0] == dma_chan[1] ||
+	    dma_chan[0] < 5 || dma_chan[0] > 7 ||
+	    dma_chan[1] < 5 || dma_chan[1] > 7)
+		return 0;
+
+	if (request_irq(irq_num, dt282x_interrupt, 0, dev->board_name, dev))
+		return 0;
+	if (request_dma(dma_chan[0], dev->board_name)) {
+		free_irq(irq_num, dev);
+		return 0;
+	}
+	if (request_dma(dma_chan[1], dev->board_name)) {
+		free_dma(dma_chan[0]);
+		free_irq(irq_num, dev);
+		return 0;
+	}
+
+	dev->irq = irq_num;
 
 	devpriv->dma_maxsize = PAGE_SIZE;
-	devpriv->dma[0].buf = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
-	devpriv->dma[1].buf = (void *)__get_free_page(GFP_KERNEL | GFP_DMA);
-	if (!devpriv->dma[0].buf || !devpriv->dma[1].buf)
+	for (i = 0; i < 2; i++) {
+		devpriv->dma[i].chan = dma_chan[i];
+		devpriv->dma[i].buf =
+			(void *)__get_free_page(GFP_KERNEL | GFP_DMA);
+		if (!devpriv->dma[i].buf)
 			return -ENOMEM;
+	}
 
 	return 0;
 }
@@ -1150,36 +1173,9 @@ static int dt282x_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		return -ENOMEM;
 
 	/* an IRQ and 2 DMA channels are required for async command support */
-	if (it->options[1] && it->options[2] && it->options[3]) {
-		unsigned int irq = it->options[1];
-		unsigned int dma1 = it->options[2];
-		unsigned int dma2 = it->options[3];
-
-		if (dma2 < dma1) {
-			unsigned int swap;
-
-			swap = dma1;
-			dma1 = dma2;
-			dma2 = swap;
-		}
-
-		if (dma1 != dma2 &&
-		    dma1 >= 5 && dma1 <= 7 &&
-		    dma2 >= 5 && dma2 <= 7) {
-			ret = request_irq(irq, dt282x_interrupt, 0,
-					  dev->board_name, dev);
-			if (ret == 0) {
-				dev->irq = irq;
-
-				ret = dt282x_grab_dma(dev, dma1, dma2);
-				if (ret < 0) {
-					dt282x_free_dma(dev);
-					free_irq(dev->irq, dev);
-					dev->irq = 0;
-				}
-			}
-		}
-	}
+	ret = dt282x_alloc_dma(dev, it);
+	if (ret)
+		return ret;
 
 	ret = comedi_alloc_subdevices(dev, 3);
 	if (ret)