staging: comedi: pcl818: tidy up dma buffer allocation

This driver uses 2 buffers for DMA. Refactor the buffer allocation to
use a for loop to remove code duplication. Remove the dev_err() messages
when __get_dma_pages() fails and change the errno returned from -EBUSY
to -ENOMEM.

Both buffers are the same size so replace the 'dmapages' and 'hwdmasize'
arrays in the private data with variables to save a bit of space.
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/pcl818.c

@@ -320,12 +320,11 @@ static const struct pcl818_board boardtypes[] = {
 };
 
 struct pcl818_private {
-
 	unsigned int dma;	/*  used DMA, 0=don't use DMA */
+	unsigned int dmapages;
+	unsigned int hwdmasize;
 	unsigned long dmabuf[2];	/*  pointers to begin of DMA buffers */
-	unsigned int dmapages[2];	/*  len of DMA buffers in PAGE_SIZEs */
 	unsigned int hwdmaptr[2];	/*  hardware address of DMA buffers */
-	unsigned int hwdmasize[2];	/*  len of DMA buffers in Bytes */
 	int next_dma_buf;	/*  which DMA buffer will be used next round */
 	long dma_runs_to_end;	/*  how many we must permorm DMA transfer to end of record */
 	unsigned long last_dma_run;	/*  how many bytes we must transfer on last DMA page */
@@ -584,13 +583,10 @@ static irqreturn_t interrupt_pcl818_ai_mode13_dma(int irq, void *d)
 		flags = claim_dma_lock();
 		set_dma_addr(devpriv->dma,
 			     devpriv->hwdmaptr[devpriv->next_dma_buf]);
-		if (devpriv->dma_runs_to_end || devpriv->neverending_ai) {
-			set_dma_count(devpriv->dma,
-				      devpriv->hwdmasize[devpriv->
-							 next_dma_buf]);
-		} else {
+		if (devpriv->dma_runs_to_end || devpriv->neverending_ai)
+			set_dma_count(devpriv->dma, devpriv->hwdmasize);
+		else
 			set_dma_count(devpriv->dma, devpriv->last_dma_run);
-		}
 		release_dma_lock(flags);
 		enable_dma(devpriv->dma);
 	}
@@ -599,7 +595,7 @@ static irqreturn_t interrupt_pcl818_ai_mode13_dma(int irq, void *d)
 	outb(0, dev->iobase + PCL818_CLRINT);	/* clear INT request */
 	ptr = (unsigned short *)devpriv->dmabuf[1 - devpriv->next_dma_buf];
 
-	len = devpriv->hwdmasize[0] >> 1;
+	len = devpriv->hwdmasize >> 1;
 	bufptr = 0;
 
 	for (i = 0; i < len; i++) {
@@ -795,14 +791,14 @@ static void pcl818_ai_mode13dma_int(int mode, struct comedi_device *dev,
 	unsigned int bytes;
 
 	disable_dma(devpriv->dma);	/*  disable dma */
-	bytes = devpriv->hwdmasize[0];
+	bytes = devpriv->hwdmasize;
 	if (!devpriv->neverending_ai) {
-		bytes = cmd->chanlist_len * cmd->stop_arg * sizeof(short);	/*  how many */
-		devpriv->dma_runs_to_end = bytes / devpriv->hwdmasize[0];	/*  how many DMA pages we must fiil */
-		devpriv->last_dma_run = bytes % devpriv->hwdmasize[0];	/* on last dma transfer must be moved */
+		bytes = cmd->chanlist_len * cmd->stop_arg * sizeof(short);
+		devpriv->dma_runs_to_end = bytes / devpriv->hwdmasize;
+		devpriv->last_dma_run = bytes % devpriv->hwdmasize;
 		devpriv->dma_runs_to_end--;
 		if (devpriv->dma_runs_to_end >= 0)
-			bytes = devpriv->hwdmasize[0];
+			bytes = devpriv->hwdmasize;
 	}
 
 	devpriv->next_dma_buf = 0;
@@ -1308,9 +1304,9 @@ static int pcl818_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 {
 	const struct pcl818_board *board = comedi_board(dev);
 	struct pcl818_private *devpriv;
-	int ret;
-	unsigned long pages;
 	struct comedi_subdevice *s;
+	int ret;
+	int i;
 
 	devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
 	if (!devpriv)
@@ -1353,20 +1349,19 @@ static int pcl818_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		}
 		devpriv->dma = it->options[2];
 
-		pages = 2;	/* we need 16KB */
-		devpriv->dmabuf[0] = __get_dma_pages(GFP_KERNEL, pages);
-		if (!devpriv->dmabuf[0])
-			/* maybe experiment with try_to_free_pages() will help .... */
-			return -EBUSY;	/* no buffer :-( */
-		devpriv->dmapages[0] = pages;
-		devpriv->hwdmaptr[0] = virt_to_bus((void *)devpriv->dmabuf[0]);
-		devpriv->hwdmasize[0] = (1 << pages) * PAGE_SIZE;
-		devpriv->dmabuf[1] = __get_dma_pages(GFP_KERNEL, pages);
-		if (!devpriv->dmabuf[1])
-			return -EBUSY;
-		devpriv->dmapages[1] = pages;
-		devpriv->hwdmaptr[1] = virt_to_bus((void *)devpriv->dmabuf[1]);
-		devpriv->hwdmasize[1] = (1 << pages) * PAGE_SIZE;
+		devpriv->dmapages = 2;	/* we need 16KB */
+		devpriv->hwdmasize = (1 << devpriv->dmapages) * PAGE_SIZE;
+
+		for (i = 0; i < 2; i++) {
+			unsigned long dmabuf;
+
+			dmabuf = __get_dma_pages(GFP_KERNEL, devpriv->dmapages);
+			if (!dmabuf)
+				return -ENOMEM;
+
+			devpriv->dmabuf[i] = dmabuf;
+			devpriv->hwdmaptr[i] = virt_to_bus((void *)dmabuf);
+		}
 	}
 
 	ret = comedi_alloc_subdevices(dev, 4);
@@ -1468,9 +1463,9 @@ static void pcl818_detach(struct comedi_device *dev)
 		if (devpriv->dma)
 			free_dma(devpriv->dma);
 		if (devpriv->dmabuf[0])
-			free_pages(devpriv->dmabuf[0], devpriv->dmapages[0]);
+			free_pages(devpriv->dmabuf[0], devpriv->dmapages);
 		if (devpriv->dmabuf[1])
-			free_pages(devpriv->dmabuf[1], devpriv->dmapages[1]);
+			free_pages(devpriv->dmabuf[1], devpriv->dmapages);
 	}
 	comedi_legacy_detach(dev);
 }