staging: comedi: pcmda12: cleanup pcmda12_ao_insn_write()

Only the last value needs to be saved for readback.

Remove the LSB and MSB macros.

(*insn_write) functions should return an errno or the number of
samples actually read. Change the final return to insn->n to
make this clear.

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>

diff --git a/drivers/staging/comedi/drivers/pcmda12.c b/drivers/staging/comedi/drivers/pcmda12.c
index c61c2c18658dd4c4d11a8eb734ddfafb5b404838..2b628944445935bffcfc28ac01a32a4dc43498a6 100644 (file)
--- a/drivers/staging/comedi/drivers/pcmda12.c
+++ b/drivers/staging/comedi/drivers/pcmda12.c
@@ -51,8 +51,6 @@ Configuration Options:
 
 #define CHANS 8
 #define IOSIZE 16
-#define LSB(x) ((unsigned char)((x) & 0xff))
-#define MSB(x) ((unsigned char)((((unsigned short)(x))>>8) & 0xff))
 #define LSB_PORT(chan) (dev->iobase + (chan)*2)
 #define MSB_PORT(chan) (LSB_PORT(chan)+1)
 
@@ -90,31 +88,25 @@ static int pcmda12_ao_insn_write(struct comedi_device *dev,
                                 unsigned int *data)
 {
        struct pcmda12_private *devpriv = dev->private;
+       unsigned int chan = CR_CHAN(insn->chanspec);
+       unsigned int val = devpriv->ao_readback[chan];
        int i;
-       int chan = CR_CHAN(insn->chanspec);
 
-       /* Writing a list of values to an AO channel is probably not
-        * very useful, but that's how the interface is defined. */
        for (i = 0; i < insn->n; ++i) {
-
-/*      /\* do this as one instruction?? *\/ */
-/*      outw(data[i], LSB_PORT(chan)); */
-
-               /* Need to do this as two instructions due to 8-bit bus?? */
-               /*  first, load the low byte */
-               outb(LSB(data[i]), LSB_PORT(chan));
-               /*  next, write the high byte */
-               outb(MSB(data[i]), MSB_PORT(chan));
-
-               /* save shadow register */
-               devpriv->ao_readback[chan] = data[i];
-
+               val = data[i];
+               outb(val & 0xff, LSB_PORT(chan));
+               outb((val >> 8) & 0xff, MSB_PORT(chan));
+
+               /*
+                * Initiate transfer if not in simultaneaous xfer
+                * mode by reading one of the AO registers.
+                */
                if (!devpriv->simultaneous_xfer_mode)
                        inb(LSB_PORT(chan));
        }
+       devpriv->ao_readback[chan] = val;
 
-       /* return the number of samples written */
-       return i;
+       return insn->n;
 }
 
 static int pcmda12_ao_insn_read(struct comedi_device *dev,