staging: comedi: pcmmio: tidy up pcmmio_start_intr()

Refactor the function to remove some indent levels.

Use pcmmio_dio_write() to write the polarity and enable paged registers
instead of using the for () loop to write each register in the pages.

The for () loop actually has a bug. It switches the page to the 'enab'
registers for the first port then switches to the 'pol' registers for
all remaining writes. It also was not using the pagelock spinlock to
protect the writes to the page registers. Using the pcmmio_dio_write()
helper ensures that the writes to the paged registers complete correctly.
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/pcmmio.c

@@ -329,11 +329,6 @@ static int pcmmio_dio_insn_config(struct comedi_device *dev,
 	return insn->n;
 }
 
-static void switch_page(struct comedi_device *dev, int page)
-{
-	outb(PCMMIO_PAGE(page), dev->iobase + PCMMIO_PAGE_LOCK_REG);
-}
-
 static void pcmmio_reset(struct comedi_device *dev)
 {
 	/* Clear all the DIO port bits */
@@ -440,46 +435,38 @@ static int pcmmio_start_intr(struct comedi_device *dev,
 			     struct comedi_subdevice *s)
 {
 	struct pcmmio_private *devpriv = dev->private;
+	struct comedi_cmd *cmd = &s->async->cmd;
+	unsigned int bits = 0;
+	unsigned int pol_bits = 0;
+	int i;
 
 	if (!devpriv->continuous && devpriv->stop_count == 0) {
 		/* An empty acquisition! */
 		s->async->events |= COMEDI_CB_EOA;
 		devpriv->active = 0;
 		return 1;
-	} else {
-		unsigned bits = 0, pol_bits = 0, n;
-		int nports, firstport, port;
-		struct comedi_cmd *cmd = &s->async->cmd;
+	}
 
 	devpriv->enabled_mask = 0;
 	devpriv->active = 1;
-		nports = 24 / CHANS_PER_PORT;
-		firstport = 0 / CHANS_PER_PORT;
 	if (cmd->chanlist) {
-			for (n = 0; n < cmd->chanlist_len; n++) {
-				bits |= (1U << CR_CHAN(cmd->chanlist[n]));
-				pol_bits |= (CR_AREF(cmd->chanlist[n])
-					     || CR_RANGE(cmd->
-							 chanlist[n]) ? 1U : 0U)
-				    << CR_CHAN(cmd->chanlist[n]);
+		for (i = 0; i < cmd->chanlist_len; i++) {
+			unsigned int chanspec = cmd->chanlist[i];
+			unsigned int chan = CR_CHAN(chanspec);
+			unsigned int range = CR_RANGE(chanspec);
+			unsigned int aref = CR_AREF(chanspec);
+
+			bits |= (1 << chan);
+			pol_bits |= (((aref || range) ? 1 : 0) << chan);
 		}
 	}
-		bits &= ((0x1 << 24) - 1) << 0;
+	bits &= ((1 << s->n_chan) - 1);
 	devpriv->enabled_mask = bits;
 
-		switch_page(dev, PCMMIO_PAGE_ENAB);
-		for (port = firstport; port < firstport + nports; ++port) {
-			unsigned enab, pol;
-
-			enab = bits >> (0 + (port - firstport) * 8) & 0xff;
-			pol = pol_bits >> (0 + (port - firstport) * 8) & 0xff;
+	/* set polarity and enable interrupts */
+	pcmmio_dio_write(dev, pol_bits, PCMMIO_PAGE_POL, 0);
+	pcmmio_dio_write(dev, bits, PCMMIO_PAGE_ENAB, 0);
 
-			/* set enab intrs for this subdev.. */
-			outb(enab, dev->iobase + PCMMIO_PAGE_REG(port));
-			switch_page(dev, PCMMIO_PAGE_POL);
-			outb(pol, dev->iobase + PCMMIO_PAGE_REG(port));
-		}
-	}
 	return 0;
 }