From 826f783a0eb15c6860d03af6d88eea3eaea34ff4 Mon Sep 17 00:00:00 2001 From: H Hartley Sweeten Date: Tue, 22 Mar 2016 11:10:32 -0700 Subject: [PATCH] staging: comedi: ni_660x: tidy up ni_660x_dio_insn_bits() Use some local variables to clarify this function. This (*insn_bits) function is a bit different from most comedi drivers. Add some comments to clarify why the shifts are used. Signed-off-by: H Hartley Sweeten Reviewed-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/drivers/ni_660x.c | 31 +++++++++++++++--------- 1 file changed, 20 insertions(+), 11 deletions(-) diff --git a/drivers/staging/comedi/drivers/ni_660x.c b/drivers/staging/comedi/drivers/ni_660x.c index f24009c98e0a..f614927411cb 100644 --- a/drivers/staging/comedi/drivers/ni_660x.c +++ b/drivers/staging/comedi/drivers/ni_660x.c @@ -780,21 +780,30 @@ static void init_tio_chip(struct comedi_device *dev, int chipset) static int ni_660x_dio_insn_bits(struct comedi_device *dev, struct comedi_subdevice *s, - struct comedi_insn *insn, unsigned int *data) + struct comedi_insn *insn, + unsigned int *data) { - unsigned int base_bitfield_channel = CR_CHAN(insn->chanspec); + unsigned int shift = CR_CHAN(insn->chanspec); + unsigned int mask = data[0] << shift; + unsigned int bits = data[1] << shift; - /* Check if we have to write some bits */ - if (data[0]) { - s->state &= ~(data[0] << base_bitfield_channel); - s->state |= (data[0] & data[1]) << base_bitfield_channel; - /* Write out the new digital output lines */ + /* + * There are 40 channels in this subdevice but only 32 are usable + * as DIO. The shift adjusts the mask/bits to account for the base + * channel in insn->chanspec. The state update can then be handled + * normally for the 32 usable channels. + */ + if (mask) { + s->state &= ~mask; + s->state |= (bits & mask); ni_660x_write(dev, 0, s->state, NI660X_DIO32_OUTPUT); } - /* on return, data[1] contains the value of the digital - * input and output lines. */ - data[1] = (ni_660x_read(dev, 0, NI660X_DIO32_INPUT) >> - base_bitfield_channel); + + /* + * Return the input channels, shifted back to account for the base + * channel. + */ + data[1] = ni_660x_read(dev, 0, NI660X_DIO32_INPUT) >> shift; return insn->n; } -- 2.20.1