staging: comedi: das1800: add analog output readback

Use the core provided readback support to allow reading back the last
value written to the analog output channels.

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/das1800.c b/drivers/staging/comedi/drivers/das1800.c
index 52a8c5b8234c37300978f1084fc356ca5f9066fe..64b5403f9a99168747f2859969c3a7ae5eefd7e1 100644 (file)
--- a/drivers/staging/comedi/drivers/das1800.c
+++ b/drivers/staging/comedi/drivers/das1800.c
@@ -91,7 +91,6 @@ Unipolar and bipolar ranges cannot be mixed in the channel/gain list.
 TODO:
        Make it automatically allocate irq and dma channels if they are not specified
        Add support for analog out on 'ao' cards
-       read insn for analog out
 */
 
 #include <linux/module.h>
@@ -341,8 +340,6 @@ struct das1800_private {
        int dma_bits;
        uint16_t *fifo_buf;     /* bounce buffer for analog input FIFO */
        unsigned long iobase2;  /* secondary io address used for analog out on 'ao' boards */
-       unsigned short ao_update_bits;  /* remembers the last write to the
-                                        * 'update' dac */
        bool ai_is_unipolar;
 };
 
@@ -1017,7 +1014,6 @@ static int das1800_ao_insn_write(struct comedi_device *dev,
                                 struct comedi_insn *insn,
                                 unsigned int *data)
 {
-       struct das1800_private *devpriv = dev->private;
        unsigned int chan = CR_CHAN(insn->chanspec);
        unsigned int update_chan = s->n_chan - 1;
        unsigned long flags;
@@ -1029,9 +1025,9 @@ static int das1800_ao_insn_write(struct comedi_device *dev,
        for (i = 0; i < insn->n; i++) {
                unsigned int val = data[i];
 
+               s->readback[chan] = val;
+
                val = comedi_offset_munge(s, val);
-               if (chan == update_chan)
-                       devpriv->ao_update_bits = val;
 
                /* load this channel (and update if it's the last channel) */
                outb(DAC(chan), dev->iobase + DAS1800_SELECT);
@@ -1039,9 +1035,10 @@ static int das1800_ao_insn_write(struct comedi_device *dev,
 
                /* update all channels */
                if (chan != update_chan) {
+                       val = comedi_offset_munge(s, s->readback[update_chan]);
+
                        outb(DAC(update_chan), dev->iobase + DAS1800_SELECT);
-                       outw(devpriv->ao_update_bits,
-                            dev->iobase + DAS1800_DAC);
+                       outw(val, dev->iobase + DAS1800_DAC);
                }
        }
        spin_unlock_irqrestore(&dev->spinlock, flags);
@@ -1318,6 +1315,10 @@ static int das1800_attach(struct comedi_device *dev,
                s->range_table  = &range_bipolar10;
                s->insn_write   = das1800_ao_insn_write;
 
+               ret = comedi_alloc_subdev_readback(s);
+               if (ret)
+                       return ret;
+
                /* initialize all channels to 0V */
                for (i = 0; i < s->n_chan; i++) {
                        outb(DAC(i), dev->iobase + DAS1800_SELECT);