[ Upstream commit 857a661020a2de3a0304edf33ad656abee100891 ]
Commit 0557344e2149 ("staging: comedi: ni_mio_common: fix local var for
32-bit read") changed the type of local variable `d` from `unsigned
short` to `unsigned int` to fix a bug introduced in
commit 9c340ac934db ("staging: comedi: ni_stc.h: add read/write
callbacks to struct ni_private") when reading AI data for NI PCI-6110
and PCI-6111 cards. Unfortunately, other parts of the function rely on
the variable being `unsigned short` when an offset value in local
variable `signbits` is added to `d` before writing the value to the
`data` array:
d += signbits;
data[n] = d;
The `signbits` variable will be non-zero in bipolar mode, and is used to
convert the hardware's 2's complement, 16-bit numbers to Comedi's
straight binary sample format (with 0 representing the most negative
voltage). This breaks because `d` is now 32 bits wide instead of 16
bits wide, so after the addition of `signbits`, `data[n]` ends up being
set to values above 65536 for negative voltages. This affects all
supported "E series" cards except PCI-6143 (and PXI-6143). Fix it by
ANDing the value written to the `data[n]` with the mask 0xffff.
Fixes: 0557344e2149 ("staging: comedi: ni_mio_common: fix local var for 32-bit read")
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/comedi/drivers/ni_mio_common.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c
index f7bcefd46b5e..c50b304ce0b4 100644
--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -2120,7 +2120,7 @@ static int ni_ai_insn_read(struct comedi_device *dev,
return -ETIME;
}
d += signbits;
- data[n] = d;
+ data[n] = d & 0xffff;
}
} else if (devpriv->is_6143) {
for (n = 0; n < insn->n; n++) {
@@ -2163,8 +2163,8 @@ static int ni_ai_insn_read(struct comedi_device *dev,
data[n] = dl;
} else {
d = ni_readw(dev, ADC_FIFO_Data_Register);
- d += signbits; /* subtle: needs to be short addition */
- data[n] = d;
+ d += signbits;
+ data[n] = d & 0xffff;
}
}
}
--
2.13.2