[PATCH 3/4] staging: comedi: ni_pcidio: Add comedi_poll support

[Ian Abbott <abbotti@xxxxxxxxx>]

This patch is ported over by me (Ian Abbott) from the out-of-tree Comedi
git repository at "git://comedi.org/git/comedi/comedi.git".

The original patch is by Nicholas Nell.

The patch adds support for the COMEDI_POLL ioctl to the ni_pcidio
driver.

Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
Cc: Nicholas Nell <nicholas.nell@xxxxxxxxxxxx>
---
 drivers/staging/comedi/drivers/ni_pcidio.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/drivers/staging/comedi/drivers/ni_pcidio.c b/drivers/staging/comedi/drivers/ni_pcidio.c
index 5145bf1..c258059 100644
--- a/drivers/staging/comedi/drivers/ni_pcidio.c
+++ b/drivers/staging/comedi/drivers/ni_pcidio.c
@@ -483,12 +483,28 @@ void ni_pcidio_event(struct comedi_device *dev, struct comedi_subdevice *s)
 	comedi_event(dev, s);
 }
 
+static int ni_pcidio_poll(struct comedi_device *dev, struct comedi_subdevice *s)
+{
+	unsigned long flags_dev, flags_mite;
+	int count;
+
+	spin_lock_irqsave(&dev->spinlock, flags_dev);
+	spin_lock_irqsave(&devpriv->mite_channel_lock, flags_mite);
+	if (devpriv->di_mite_chan)
+		mite_sync_input_dma(devpriv->di_mite_chan, s->async);
+	spin_unlock_irqrestore(&devpriv->mite_channel_lock, flags_mite);
+	count = s->async->buf_write_count - s->async->buf_read_count;
+	spin_unlock_irqrestore(&dev->spinlock, flags_dev);
+	return count;
+}
+
 static irqreturn_t nidio_interrupt(int irq, void *d)
 {
 	struct comedi_device *dev = d;
 	struct comedi_subdevice *s = dev->subdevices;
 	struct comedi_async *async = s->async;
 	struct mite_struct *mite = devpriv->mite;
+	unsigned long flags_dev;
 
 	/* int i, j; */
 	long int AuxData = 0;
@@ -506,6 +522,9 @@ static irqreturn_t nidio_interrupt(int irq, void *d)
 		return IRQ_NONE;
 	}
 
+	/* Lock to avoid race with comedi_poll */
+	spin_lock_irqsave(&dev->spinlock, flags_dev);
+
 	status = readb(devpriv->mite->daq_io_addr +
 		       Interrupt_And_Window_Status);
 	flags = readb(devpriv->mite->daq_io_addr + Group_1_Flags);
@@ -646,6 +665,8 @@ out:
 		       Master_DMA_And_Interrupt_Control);
 	}
 #endif
+
+	spin_unlock_irqrestore(&dev->spinlock, flags_dev);
 	return IRQ_HANDLED;
 }
 
@@ -1252,6 +1273,7 @@ static int nidio_attach(struct comedi_device *dev, struct comedi_devconfig *it)
 		s->len_chanlist = 32;	/* XXX */
 		s->buf_change = &ni_pcidio_change;
 		s->async_dma_dir = DMA_BIDIRECTIONAL;
+		s->poll = &ni_pcidio_poll;
 
 		writel(0, devpriv->mite->daq_io_addr + Port_IO(0));
 		writel(0, devpriv->mite->daq_io_addr + Port_Pin_Directions(0));
-- 
1.7.8.2

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