staging: comedi: c6xdigio: add readback of last pwm channel values

Add and (*insn_read) for the PWM subdevice to allow reading back the
last value written to the channels.

There are only 2 PWM channels and they have a maxdata of 500. Pack
the last values in the subdevice 'state' instead of adding a private
data struct to this driver.

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/c6xdigio.c b/drivers/staging/comedi/drivers/c6xdigio.c
index 20a5dfe..4114cf2 100644 (file)
--- a/drivers/staging/comedi/drivers/c6xdigio.c
+++ b/drivers/staging/comedi/drivers/c6xdigio.c
@@ -162,13 +162,41 @@ static int c6xdigio_pwm_insn_write(struct comedi_device *dev,
                                   unsigned int *data)
 {
        unsigned int chan = CR_CHAN(insn->chanspec);
+       unsigned int val = (s->state >> (16 * chan)) & 0xffff;
        int i;
 
        for (i = 0; i < insn->n; i++) {
-               c6xdigio_pwm_write(dev, chan, data[i]);
-               /*    devpriv->ao_readback[chan] = data[i]; */
+               val = data[i];
+               c6xdigio_pwm_write(dev, chan, val);
        }
-       return i;
+
+       /*
+        * There are only 2 PWM channels and they have a maxdata of 500.
+        * Instead of allocating private data to save the values in for
+        * readback this driver just packs the values for the two channels
+        * in the s->state.
+        */
+       s->state &= (0xffff << (16 * chan));
+       s->state |= (val << (16 * chan));
+
+       return insn->n;
+}
+
+static int c6xdigio_pwm_insn_read(struct comedi_device *dev,
+                                 struct comedi_subdevice *s,
+                                 struct comedi_insn *insn,
+                                 unsigned int *data)
+{
+       unsigned int chan = CR_CHAN(insn->chanspec);
+       unsigned int val;
+       int i;
+
+       val = (s->state >> (16 * chan)) & 0xffff;
+
+       for (i = 0; i < insn->n; i++)
+               data[i] = val;
+
+       return insn->n;
 }
 
 static int c6xdigio_encoder_insn_read(struct comedi_device *dev,
@@ -243,6 +271,7 @@ static int c6xdigio_attach(struct comedi_device *dev,
        s->maxdata      = 500;
        s->range_table  = &range_unknown;
        s->insn_write   = c6xdigio_pwm_insn_write;
+       s->insn_read    = c6xdigio_pwm_insn_read;
 
        s = &dev->subdevices[1];
        /* encoder (counter) subdevice */