staging: comedi: usbdux: tidy up usbdux_ai_insn_read()

Rename the local variable used for the private data pointer to the
comedi "norm".

Remove the unnecessary sanity check of the private data pointer. This
function can only be called is the private data was allocated during
the attach.

Tidy up the exit path using goto to ensure that the semaphore is
released.

Return -EBUSY instead of 0 if the (*insn_read) cannot be done because
a command is running.
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/usbdux.c

@@ -973,50 +973,45 @@ static int usbdux_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
 /* Mode 0 is used to get a single conversion on demand */
 static int usbdux_ai_insn_read(struct comedi_device *dev,
 			       struct comedi_subdevice *s,
-			       struct comedi_insn *insn, unsigned int *data)
+			       struct comedi_insn *insn,
+			       unsigned int *data)
 {
+	struct usbdux_private *devpriv = dev->private;
+	unsigned int chan = CR_CHAN(insn->chanspec);
+	unsigned int range = CR_RANGE(insn->chanspec);
+	unsigned int val;
+	int ret = -EBUSY;
 	int i;
-	unsigned int one = 0;
-	int chan, range;
-	int err;
-	struct usbdux_private *this_usbduxsub = dev->private;
 
-	if (!this_usbduxsub)
-		return 0;
+	down(&devpriv->sem);
 
-	down(&this_usbduxsub->sem);
-	if (this_usbduxsub->ai_cmd_running) {
-		up(&this_usbduxsub->sem);
-		return 0;
-	}
+	if (devpriv->ai_cmd_running)
+		goto ai_read_exit;
 
-	/* sample one channel */
-	chan = CR_CHAN(insn->chanspec);
-	range = CR_RANGE(insn->chanspec);
 	/* set command for the first channel */
-	this_usbduxsub->dux_commands[1] = create_adc_command(chan, range);
+	devpriv->dux_commands[1] = create_adc_command(chan, range);
 
 	/* adc commands */
-	err = send_dux_commands(dev, SENDSINGLEAD);
-	if (err < 0) {
-		up(&this_usbduxsub->sem);
-		return err;
-	}
+	ret = send_dux_commands(dev, SENDSINGLEAD);
+	if (ret < 0)
+		goto ai_read_exit;
 
 	for (i = 0; i < insn->n; i++) {
-		err = receive_dux_commands(dev, SENDSINGLEAD);
-		if (err < 0) {
-			up(&this_usbduxsub->sem);
-			return 0;
-		}
-		one = le16_to_cpu(this_usbduxsub->insn_buffer[1]);
-		if (CR_RANGE(insn->chanspec) <= 1)
-			one = one ^ 0x800;
+		ret = receive_dux_commands(dev, SENDSINGLEAD);
+		if (ret < 0)
+			goto ai_read_exit;
+
+		val = le16_to_cpu(devpriv->insn_buffer[1]);
+		if (range <= 1)
+			val ^= 0x800;
 
-		data[i] = one;
+		data[i] = val;
 	}
-	up(&this_usbduxsub->sem);
-	return i;
+
+ai_read_exit:
+	up(&devpriv->sem);
+
+	return ret ? ret : insn->n;
 }
 
 /************************************/