staging: comedi: rti800: tidy up analog input 'muxgain'

Refactor the code that determines the 'delay' after setting the muxgain
register to remove the BUG_ON().

Change the private data 'muxgain_bits' to an unsigned char, the muxgain
register is only 8-bits.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/rti800.c b/drivers/staging/comedi/drivers/rti800.c
index 30d7245b6baec2f42c6144731cf094e3b56920b7..e043ed91cdf0892e2fd15696e7ebf90d04fdc759 100644 (file)
--- a/drivers/staging/comedi/drivers/rti800.c
+++ b/drivers/staging/comedi/drivers/rti800.c
@@ -156,24 +156,22 @@ struct rti800_private {
        bool dac_2comp[2];
        const struct comedi_lrange *ao_range_type_list[2];
        unsigned int ao_readback[2];
-       int muxgain_bits;
+       unsigned char muxgain_bits;
 };
 
 #define RTI800_TIMEOUT 100
 
-/* settling delay times in usec for different gains */
-static const int gaindelay[] = { 10, 20, 40, 80 };
-
 static int rti800_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 rti800_private *devpriv = dev->private;
        unsigned int chan = CR_CHAN(insn->chanspec);
        unsigned int gain = CR_RANGE(insn->chanspec);
+       unsigned char muxgain_bits;
        int i, t;
        int status;
-       unsigned muxgain_bits;
 
        inb(dev->iobase + RTI800_ADCHI);
        outb(0, dev->iobase + RTI800_CLRFLAGS);
@@ -182,11 +180,16 @@ static int rti800_ai_insn_read(struct comedi_device *dev,
        if (muxgain_bits != devpriv->muxgain_bits) {
                devpriv->muxgain_bits = muxgain_bits;
                outb(devpriv->muxgain_bits, dev->iobase + RTI800_MUXGAIN);
-               /* without a delay here, the RTI_OVERRUN bit
-                * gets set, and you will have an error. */
+               /*
+                * Without a delay here, the RTI_OVERRUN bit
+                * gets set, and you will have an error.
+                */
                if (insn->n > 0) {
-                       BUG_ON(gain >= ARRAY_SIZE(gaindelay));
-                       udelay(gaindelay[gain]);
+                       int delay = (gain == 0) ? 10 :
+                                   (gain == 1) ? 20 :
+                                   (gain == 2) ? 40 : 80;
+
+                       udelay(delay);
                }
        }
 
@@ -330,7 +333,8 @@ static int rti800_attach(struct comedi_device *dev, struct comedi_devconfig *it)
        devpriv->adc_coding = it->options[4];
        devpriv->dac_2comp[0] = (it->options[6] == 0);
        devpriv->dac_2comp[1] = (it->options[8] == 0);
-       devpriv->muxgain_bits = -1;
+       /* invalid, forces the MUXGAIN register to be set when first used */
+       devpriv->muxgain_bits = 0xff;
 
        ret = comedi_alloc_subdevices(dev, 4);
        if (ret)