diff options
| author | Ian Abbott <abbotti@mev.co.uk> | 2016-11-14 20:16:22 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-09 08:07:44 +0100 |
| commit | 01b6089b5622bbcb2c77ce655a218fb7b8ccd77d (patch) | |
| tree | 22357894d6eb1533dbd5a7acc7e8cfaad8bb5e71 | |
| parent | 5283a7bedbcbdfa654c8a4d7fb314d734a56e544 (diff) | |
staging: comedi: ni_mio_common: fix E series ni_ai_insn_read() data
commit 857a661020a2de3a0304edf33ad656abee100891 upstream.
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@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/staging/comedi/drivers/ni_mio_common.c | 6 |
1 files 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 a575772efeb1..c975f6e8be49 100644 --- a/drivers/staging/comedi/drivers/ni_mio_common.c +++ b/drivers/staging/comedi/drivers/ni_mio_common.c @@ -1972,7 +1972,7 @@ 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++) { @@ -2017,8 +2017,8 @@ static int ni_ai_insn_read(struct comedi_device *dev, data[n] = dl; } else { d = ni_readw(dev, NI_E_AI_FIFO_DATA_REG); - d += signbits; /* subtle: needs to be short addition */ - data[n] = d; + d += signbits; + data[n] = d & 0xffff; } } } |