Staging: comedi: clean up conditional statement in addi_apci_3xxx.c

In this conditional statement, if (chan < 16), but the instruction passed
in data[0] is INSN_CONFIG_DIO_QUERY, the function does not return early,
but the else-branch does not get executed either.  As a result, mask
would be used uninitialized in the next line.  We want
comedi_dio_insn_config() to use a chan_mask based on the chanspec for the
INSN_CONFIG_DIO_QUERY instruction, so mask should be initialized to 0.
Then, if instead the instruction is INSN_CONFIG_DIO_{INPUT,OUTPUT}, we
return an error if (chan < 16) as these are invalid instructions for
ports 0 and 1, or update the mask otherwise, so all the io_bits are
modified for port 2.  This ensures that mask is always initialized by the
time it is used.

Signed-off-by: Chase Southwood <chase.southwood@yahoo.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/addi_apci_3xxx.c b/drivers/staging/comedi/drivers/addi_apci_3xxx.c
index ceadf8e..1f3b668 100644 (file)
--- a/drivers/staging/comedi/drivers/addi_apci_3xxx.c
+++ b/drivers/staging/comedi/drivers/addi_apci_3xxx.c
@@ -680,7 +680,7 @@ static int apci3xxx_dio_insn_config(struct comedi_device *dev,
                                    unsigned int *data)
 {
        unsigned int chan = CR_CHAN(insn->chanspec);
-       unsigned int mask;
+       unsigned int mask = 0;
        int ret;
 
        /*
@@ -688,12 +688,13 @@ static int apci3xxx_dio_insn_config(struct comedi_device *dev,
         * Port 1 (channels 8-15) are always outputs
         * Port 2 (channels 16-23) are programmable i/o
         */
-       if (chan < 16) {
-               if (data[0] != INSN_CONFIG_DIO_QUERY)
+       if (data[0] != INSN_CONFIG_DIO_QUERY) {
+               /* ignore all other instructions for ports 0 and 1 */
+               if (chan < 16)
                        return -EINVAL;
-       } else {
-               /* changing any channel in port 2 changes the entire port */
-               mask = 0xff0000;
+               else
+                       /* changing any channel in port 2 changes the entire port */
+                       mask = 0xff0000;
        }
 
        ret = comedi_dio_insn_config(dev, s, insn, data, mask);