staging: comedi: ni_tio: Use data[insn->n-1] in ni_tio_insn_write()

The `insn_write` handler for the counter subdevices
(`ni_tio_insn_write()`) writes a single data value `data[0]` to the
channel.  Technically, `insn->n` specifies the number of successive
values from `data[]` to write to the channel, but when there is little
benefit in writing multiple data values, the usual Comedi convention is
to just write the last data value `data[insn->n - 1]`.  Change the
function to follow that convention and use `data[insn->n - 1]` instead
of `data[0]`.  (In practice, `insn->n` would normally be 1 anyway.)

Also follow the usual Comedi convention and return `insn->n` from the
handler to indicate success instead of 0 (although any non-negative
return value will do).

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/ni_tio.c b/drivers/staging/comedi/drivers/ni_tio.c
index 048cb35..943c517 100644 (file)
--- a/drivers/staging/comedi/drivers/ni_tio.c
+++ b/drivers/staging/comedi/drivers/ni_tio.c
@@ -1682,9 +1682,11 @@ int ni_tio_insn_write(struct comedi_device *dev,
        unsigned int cidx = counter->counter_index;
        unsigned int chip = counter->chip_index;
        unsigned int load_reg;
+       unsigned int load_val;
 
        if (insn->n < 1)
                return 0;
+       load_val = data[insn->n - 1];
        switch (channel) {
        case 0:
                /*
@@ -1697,7 +1699,7 @@ int ni_tio_insn_write(struct comedi_device *dev,
                 * load register is already selected.
                 */
                load_reg = ni_tio_next_load_register(counter);
-               ni_tio_write(counter, data[0], load_reg);
+               ni_tio_write(counter, load_val, load_reg);
                ni_tio_set_bits_transient(counter, NITIO_CMD_REG(cidx),
                                          0, 0, GI_LOAD);
                /* restore load reg */
@@ -1705,17 +1707,17 @@ int ni_tio_insn_write(struct comedi_device *dev,
                             load_reg);
                break;
        case 1:
-               counter_dev->regs[chip][NITIO_LOADA_REG(cidx)] = data[0];
-               ni_tio_write(counter, data[0], NITIO_LOADA_REG(cidx));
+               counter_dev->regs[chip][NITIO_LOADA_REG(cidx)] = load_val;
+               ni_tio_write(counter, load_val, NITIO_LOADA_REG(cidx));
                break;
        case 2:
-               counter_dev->regs[chip][NITIO_LOADB_REG(cidx)] = data[0];
-               ni_tio_write(counter, data[0], NITIO_LOADB_REG(cidx));
+               counter_dev->regs[chip][NITIO_LOADB_REG(cidx)] = load_val;
+               ni_tio_write(counter, load_val, NITIO_LOADB_REG(cidx));
                break;
        default:
                return -EINVAL;
        }
-       return 0;
+       return insn->n;
 }
 EXPORT_SYMBOL_GPL(ni_tio_insn_write);