staging: comedi: adv_pci1710: Fix endian problem for AI command data

commit b2e7863 upstream.

The analog input subdevice supports Comedi asynchronous commands that
use Comedi's 16-bit sample format.  However, the calls to
`comedi_buf_write_samples()` are passing the address of a 32-bit integer
variable.  On bigendian machines, this will copy 2 bytes from the wrong
end of the 32-bit value.  Fix it by changing the type of the variables
holding the sample value to `unsigned short`.  The type of the `val`
parameter of `pci1710_ai_read_sample()` is changed to `unsigned short *`
accordingly.  The type of the `val` variable in `pci1710_ai_insn_read()`
is also changed to `unsigned short` since its address is passed to
`pci1710_ai_read_sample()`.

Fixes: a9c3a01 ("staging: comedi: adv_pci1710: use comedi_buf_write_samples()")
Cc: <stable@vger.kernel.org> # 4.0+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20210223143055.257402-4-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/adv_pci1710.c

@@ -300,11 +300,11 @@ static int pci1710_ai_eoc(struct comedi_device *dev,
 static int pci1710_ai_read_sample(struct comedi_device *dev,
 				  struct comedi_subdevice *s,
 				  unsigned int cur_chan,
-				  unsigned int *val)
+				  unsigned short *val)
 {
 	const struct boardtype *board = dev->board_ptr;
 	struct pci1710_private *devpriv = dev->private;
-	unsigned int sample;
+	unsigned short sample;
 	unsigned int chan;
 
 	sample = inw(dev->iobase + PCI171X_AD_DATA_REG);
@@ -345,7 +345,7 @@ static int pci1710_ai_insn_read(struct comedi_device *dev,
 	pci1710_ai_setup_chanlist(dev, s, &insn->chanspec, 1, 1);
 
 	for (i = 0; i < insn->n; i++) {
-		unsigned int val;
+		unsigned short val;
 
 		/* start conversion */
 		outw(0, dev->iobase + PCI171X_SOFTTRG_REG);
@@ -395,7 +395,7 @@ static void pci1710_handle_every_sample(struct comedi_device *dev,
 {
 	struct comedi_cmd *cmd = &s->async->cmd;
 	unsigned int status;
-	unsigned int val;
+	unsigned short val;
 	int ret;
 
 	status = inw(dev->iobase + PCI171X_STATUS_REG);
@@ -455,7 +455,7 @@ static void pci1710_handle_fifo(struct comedi_device *dev,
 	}
 
 	for (i = 0; i < devpriv->max_samples; i++) {
-		unsigned int val;
+		unsigned short val;
 		int ret;
 
 		ret = pci1710_ai_read_sample(dev, s, s->async->cur_chan, &val);