staging: comedi: das1800: use comedi_async 'scans_done' to detect EOA

Remove the private data member 'count' and use the comedi_async 'scans_done'
member to detect the end-of-acquisition.

Use the comedi_nsamples_left() helper to get the number of samples to actually
add to the async buffer.
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/das1800.c

@@ -421,7 +421,6 @@ static const struct das1800_board das1800_boards[] = {
 };
 
 struct das1800_private {
-	unsigned int count;	/* number of data points left to be taken */
 	unsigned int divisor1;	/* value to load into board's counter 1 for timed conversions */
 	unsigned int divisor2;	/* value to load into board's counter 2 for timed conversions */
 	int irq_dma_bits;	/* bits for control register b */
@@ -479,41 +478,33 @@ static void das1800_handle_fifo_half_full(struct comedi_device *dev,
 					  struct comedi_subdevice *s)
 {
 	struct das1800_private *devpriv = dev->private;
-	int numPoints = 0;	/* number of points to read */
-	struct comedi_cmd *cmd = &s->async->cmd;
+	unsigned int nsamples = comedi_nsamples_left(s, FIFO_SIZE / 2);
 
-	numPoints = FIFO_SIZE / 2;
-	/* if we only need some of the points */
-	if (cmd->stop_src == TRIG_COUNT && devpriv->count < numPoints)
-		numPoints = devpriv->count;
-	insw(dev->iobase + DAS1800_FIFO, devpriv->ai_buf0, numPoints);
-	munge_data(dev, devpriv->ai_buf0, numPoints);
-	comedi_buf_write_samples(s, devpriv->ai_buf0, numPoints);
-	if (cmd->stop_src == TRIG_COUNT)
-		devpriv->count -= numPoints;
+	insw(dev->iobase + DAS1800_FIFO, devpriv->ai_buf0, nsamples);
+	munge_data(dev, devpriv->ai_buf0, nsamples);
+	comedi_buf_write_samples(s, devpriv->ai_buf0, nsamples);
 }
 
 static void das1800_handle_fifo_not_empty(struct comedi_device *dev,
 					  struct comedi_subdevice *s)
 {
-	struct das1800_private *devpriv = dev->private;
+	struct comedi_cmd *cmd = &s->async->cmd;
 	unsigned short dpnt;
 	int unipolar;
-	struct comedi_cmd *cmd = &s->async->cmd;
 
 	unipolar = inb(dev->iobase + DAS1800_CONTROL_C) & UB;
 
 	while (inb(dev->iobase + DAS1800_STATUS) & FNE) {
-		if (cmd->stop_src == TRIG_COUNT && devpriv->count == 0)
-			break;
 		dpnt = inw(dev->iobase + DAS1800_FIFO);
 		/* convert to unsigned type if we are in a bipolar mode */
 		if (!unipolar)
 			;
 		dpnt = munge_bipolar_sample(dev, dpnt);
 		comedi_buf_write_samples(s, &dpnt, 1);
-		if (cmd->stop_src == TRIG_COUNT)
-			devpriv->count--;
+
+		if (cmd->stop_src == TRIG_COUNT &&
+		    s->async->scans_done >= cmd->stop_arg)
+			break;
 	}
 }
 
@@ -524,8 +515,8 @@ static void das1800_flush_dma_channel(struct comedi_device *dev,
 				      unsigned int channel, uint16_t *buffer)
 {
 	struct das1800_private *devpriv = dev->private;
-	unsigned int num_bytes, num_samples;
-	struct comedi_cmd *cmd = &s->async->cmd;
+	unsigned int nbytes;
+	unsigned int nsamples;
 
 	disable_dma(channel);
 
@@ -534,17 +525,12 @@ static void das1800_flush_dma_channel(struct comedi_device *dev,
 	clear_dma_ff(channel);
 
 	/*  figure out how many points to read */
-	num_bytes = devpriv->dma_transfer_size - get_dma_residue(channel);
-	num_samples = comedi_bytes_to_samples(s, num_bytes);
-
-	/* if we only need some of the points */
-	if (cmd->stop_src == TRIG_COUNT && devpriv->count < num_samples)
-		num_samples = devpriv->count;
+	nbytes = devpriv->dma_transfer_size - get_dma_residue(channel);
+	nsamples = comedi_bytes_to_samples(s, nbytes);
+	nsamples = comedi_nsamples_left(s, nsamples);
 
-	munge_data(dev, buffer, num_samples);
-	comedi_buf_write_samples(s, buffer, num_samples);
-	if (cmd->stop_src == TRIG_COUNT)
-		devpriv->count -= num_samples;
+	munge_data(dev, buffer, nsamples);
+	comedi_buf_write_samples(s, buffer, nsamples);
 }
 
 /* flushes remaining data from board when external trigger has stopped acquisition
@@ -668,7 +654,8 @@ static void das1800_ai_handler(struct comedi_device *dev)
 		else
 			das1800_handle_fifo_not_empty(dev, s);
 		async->events |= COMEDI_CB_EOA;
-	} else if (cmd->stop_src == TRIG_COUNT && devpriv->count == 0) {	/*  stop_src TRIG_COUNT */
+	} else if (cmd->stop_src == TRIG_COUNT &&
+		   async->scans_done >= cmd->stop_arg) {
 		async->events |= COMEDI_CB_EOA;
 	}
 
@@ -1100,9 +1087,6 @@ static int das1800_ai_do_cmd(struct comedi_device *dev,
 		/*  interrupt fifo half full */
 		devpriv->irq_dma_bits |= FIMD;
 	}
-	/*  determine how many conversions we need */
-	if (cmd->stop_src == TRIG_COUNT)
-		devpriv->count = cmd->stop_arg * cmd->chanlist_len;
 
 	das1800_cancel(dev, s);