| From 857a661020a2de3a0304edf33ad656abee100891 Mon Sep 17 00:00:00 2001 |
| From: Ian Abbott <abbotti@mev.co.uk> |
| Date: Mon, 14 Nov 2016 20:16:22 +0000 |
| Subject: staging: comedi: ni_mio_common: fix E series ni_ai_insn_read() data |
| |
| From: Ian Abbott <abbotti@mev.co.uk> |
| |
| 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> |
| |
| --- |
| drivers/staging/comedi/drivers/ni_mio_common.c | 5 ++--- |
| 1 file changed, 2 insertions(+), 3 deletions(-) |
| |
| --- a/drivers/staging/comedi/drivers/ni_mio_common.c |
| +++ b/drivers/staging/comedi/drivers/ni_mio_common.c |
| @@ -1875,7 +1875,7 @@ static int ni_ai_insn_read(struct comedi |
| return -ETIME; |
| } |
| d += signbits; |
| - data[n] = d; |
| + data[n] = d & 0xffff; |
| } |
| } else if (devpriv->is_6143) { |
| for (n = 0; n < insn->n; n++) { |
| @@ -1924,9 +1924,8 @@ static int ni_ai_insn_read(struct comedi |
| data[n] = dl; |
| } else { |
| d = ni_readw(dev, NI_E_AI_FIFO_DATA_REG); |
| - /* subtle: needs to be short addition */ |
| d += signbits; |
| - data[n] = d; |
| + data[n] = d & 0xffff; |
| } |
| } |
| } |