Commit 023bea74 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman

staging: comedi: das1800: fix possible NULL dereference

commit d375278d upstream.

DMA is optional with this driver. If it was not enabled the devpriv->dma
pointer will be NULL.

Fix the possible NULL pointer dereference when trying to disable the DMA
channels in das1800_ai_cancel() and tidy up the comments to fix the
checkpatch.pl issues:
WARNING: line over 80 characters

It's probably harmless in das1800_ai_setup_dma() because the 'desc' pointer
will not be used if DMA is disabled but fix it there also.

Fixes: 99dfc335 ("staging: comedi: das1800: remove depends on ISA_DMA_API limitation")
Signed-off-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 53c24ba2
......@@ -567,14 +567,17 @@ static int das1800_cancel(struct comedi_device *dev, struct comedi_subdevice *s)
struct comedi_isadma_desc *desc;
int i;
outb(0x0, dev->iobase + DAS1800_STATUS); /* disable conversions */
outb(0x0, dev->iobase + DAS1800_CONTROL_B); /* disable interrupts and dma */
outb(0x0, dev->iobase + DAS1800_CONTROL_A); /* disable and clear fifo and stop triggering */
for (i = 0; i < 2; i++) {
desc = &dma->desc[i];
if (desc->chan)
comedi_isadma_disable(desc->chan);
/* disable and stop conversions */
outb(0x0, dev->iobase + DAS1800_STATUS);
outb(0x0, dev->iobase + DAS1800_CONTROL_B);
outb(0x0, dev->iobase + DAS1800_CONTROL_A);
if (dma) {
for (i = 0; i < 2; i++) {
desc = &dma->desc[i];
if (desc->chan)
comedi_isadma_disable(desc->chan);
}
}
return 0;
......@@ -934,13 +937,14 @@ static void das1800_ai_setup_dma(struct comedi_device *dev,
{
struct das1800_private *devpriv = dev->private;
struct comedi_isadma *dma = devpriv->dma;
struct comedi_isadma_desc *desc = &dma->desc[0];
struct comedi_isadma_desc *desc;
unsigned int bytes;
if ((devpriv->irq_dma_bits & DMA_ENABLED) == 0)
return;
dma->cur_dma = 0;
desc = &dma->desc[0];
/* determine a dma transfer size to fill buffer in 0.3 sec */
bytes = das1800_ai_transfer_size(dev, s, desc->maxsize, 300000000);
......
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