ni_at_ao: don't access *data when insn->n == 0

Due to recent change to do_insnlist_ioctl() and do_insn_ioctl(), the
'data' pointer will be NULL when insn->n == 0.  Do not access *data
in this case.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>

diff --git a/comedi/drivers/ni_at_ao.c b/comedi/drivers/ni_at_ao.c
index 17d055e61545e8aa0d480175a3f21951cc3ddfcb..d0dcf45e59f7adc677b9b34fd5c5a3e8ffd82773 100644 (file)
--- a/comedi/drivers/ni_at_ao.c
+++ b/comedi/drivers/ni_at_ao.c
@@ -434,6 +434,9 @@ static int atao_calib_insn_write(comedi_device * dev, comedi_subdevice * s,
        unsigned int bitstring, bit;
        unsigned int chan = CR_CHAN(insn->chanspec);
 
+       if (insn->n == 0)
+               return 0;
+
        bitstring = ((chan & 0x7) << 8) | (data[insn->n - 1] & 0xff);
 
        for (bit = 1 << (11 - 1); bit; bit >>= 1) {