staging: comedi: amplc_pci230: use comedi_async 'scans_done' to detect AI EOA

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

Use the comedi_nsamples_left() helper to work out the number of 'wake' samples in
pci230_ai_update_fifo_trigger_level() and the number of 'todo' samples actually
added to the async buffer in pci230_handle_ai().

Remove the unnecessary COMEDI_CB_OVERFLOW event for the hardware FIFO overflow
error. The COMEDI_CB_ERROR event will terminate the command.

comedi_buf_write_samples() can fail if the async buffer does not have room for
the sample. The it will set the COMEDI_CB_OVERFLOW event and return 0. Detect
this and quit trying to read and add more samples. The event will terminate the
command.
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/amplc_pci230.c

@@ -490,7 +490,6 @@ struct pci230_private {
 	spinlock_t ai_stop_spinlock;	/* Spin lock for stopping AI command */
 	spinlock_t ao_stop_spinlock;	/* Spin lock for stopping AO command */
 	unsigned long daqio;		/* PCI230's DAQ I/O space */
-	unsigned int ai_scan_count;	/* Number of AI scans remaining */
 	int intr_cpuid;			/* ID of CPU running ISR */
 	unsigned short hwver;		/* Hardware version (for '+' models) */
 	unsigned short adccon;		/* ADCCON register value */
@@ -1720,19 +1719,15 @@ static void pci230_ai_update_fifo_trigger_level(struct comedi_device *dev,
 {
 	struct pci230_private *devpriv = dev->private;
 	struct comedi_cmd *cmd = &s->async->cmd;
-	unsigned int scanlen = cmd->scan_end_arg;
 	unsigned int wake;
 	unsigned short triglev;
 	unsigned short adccon;
 
 	if (cmd->flags & CMDF_WAKE_EOS)
-		wake = scanlen - s->async->cur_chan;
-	else if (cmd->stop_src != TRIG_COUNT ||
-		 devpriv->ai_scan_count >= PCI230_ADC_FIFOLEVEL_HALFFULL ||
-		 scanlen >= PCI230_ADC_FIFOLEVEL_HALFFULL)
-		wake = PCI230_ADC_FIFOLEVEL_HALFFULL;
+		wake = cmd->scan_end_arg - s->async->cur_chan;
 	else
-		wake = devpriv->ai_scan_count * scanlen - s->async->cur_chan;
+		wake = comedi_nsamples_left(s, PCI230_ADC_FIFOLEVEL_HALFFULL);
+
 	if (wake >= PCI230_ADC_FIFOLEVEL_HALFFULL) {
 		triglev = PCI230_ADC_INT_FIFO_HALF;
 	} else if (wake > 1 && devpriv->hwver > 0) {
@@ -2025,8 +2020,6 @@ static void pci230_handle_ai(struct comedi_device *dev,
 	struct pci230_private *devpriv = dev->private;
 	struct comedi_async *async = s->async;
 	struct comedi_cmd *cmd = &async->cmd;
-	unsigned int scanlen = cmd->scan_end_arg;
-	unsigned int events = 0;
 	unsigned int status_fifo;
 	unsigned int i;
 	unsigned int todo;
@@ -2034,20 +2027,10 @@ static void pci230_handle_ai(struct comedi_device *dev,
 	unsigned short val;
 
 	/* Determine number of samples to read. */
-	if (cmd->stop_src != TRIG_COUNT) {
-		todo = PCI230_ADC_FIFOLEVEL_HALFFULL;
-	} else if (devpriv->ai_scan_count == 0) {
-		todo = 0;
-	} else if (devpriv->ai_scan_count > PCI230_ADC_FIFOLEVEL_HALFFULL ||
-		   scanlen > PCI230_ADC_FIFOLEVEL_HALFFULL) {
-		todo = PCI230_ADC_FIFOLEVEL_HALFFULL;
-	} else {
-		todo = devpriv->ai_scan_count * scanlen - async->cur_chan;
-		if (todo > PCI230_ADC_FIFOLEVEL_HALFFULL)
-			todo = PCI230_ADC_FIFOLEVEL_HALFFULL;
-	}
+	todo = comedi_nsamples_left(s, PCI230_ADC_FIFOLEVEL_HALFFULL);
 	if (todo == 0)
 		return;
+
 	fifoamount = 0;
 	for (i = 0; i < todo; i++) {
 		if (fifoamount == 0) {
@@ -2059,7 +2042,7 @@ static void pci230_handle_ai(struct comedi_device *dev,
 				 * unnoticed by the caller.
 				 */
 				dev_err(dev->class_dev, "AI FIFO overrun\n");
-				events |= COMEDI_CB_OVERFLOW | COMEDI_CB_ERROR;
+				async->events |= COMEDI_CB_ERROR;
 				break;
 			} else if (status_fifo & PCI230_ADC_FIFO_EMPTY) {
 				/* FIFO empty. */
@@ -2080,21 +2063,21 @@ static void pci230_handle_ai(struct comedi_device *dev,
 		}
 
 		val = pci230_ai_read(dev);
-		comedi_buf_write_samples(s, &val, 1);
+		if (!comedi_buf_write_samples(s, &val, 1))
+			break;
 
 		fifoamount--;
-		if (async->cur_chan == 0)
-			devpriv->ai_scan_count--;
+
+		if (cmd->stop_src == TRIG_COUNT &&
+		    async->scans_done >= cmd->stop_arg) {
+			async->events |= COMEDI_CB_EOA;
+			break;
 		}
-	if (cmd->stop_src == TRIG_COUNT && devpriv->ai_scan_count == 0) {
-		/* End of acquisition. */
-		events |= COMEDI_CB_EOA;
 	}
-	async->events |= events;
-	if (!(async->events & COMEDI_CB_CANCEL_MASK)) {
-		/* update FIFO interrupt trigger level */
+
+	/* update FIFO interrupt trigger level if still running */
+	if (!(async->events & COMEDI_CB_CANCEL_MASK))
 		pci230_ai_update_fifo_trigger_level(dev, s);
-	}
 }
 
 static int pci230_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
@@ -2130,8 +2113,6 @@ static int pci230_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 	if (!pci230_claim_shared(dev, res_mask, OWNER_AICMD))
 		return -EBUSY;
 
-	devpriv->ai_scan_count = cmd->stop_arg;
-
 	/*
 	 * Steps:
 	 * - Set channel scan list.