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authorIan Abbott <abbotti@mev.co.uk>2013-02-27 12:52:45 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-04 06:09:07 +0800
commit5e6af63de116db55be85da4374441f7963d11281 (patch)
tree57d7a705fefbe695381bff7516b6bf7acc2d1e6c
parentd81d788db85abd39fd7753e2482f748c48de202a (diff)
staging: comedi: ni_labpc: correct differential channel sequence for AI commands
Commit 4c4bc25d0fa6beaf054c0b4c3b324487f266c820 upstream. Tuomas <tvainikk _at_ gmail _dot_ com> reported problems getting meaningful output from a Lab-PC+ in differential mode for AI cmds, but AI insn reads gave correct readings. He tracked it down to two problems, one of which is addressed by this patch. It seems the setting of the channel bits for particular scanning modes was incorrect for differential mode. (Only half the number of channels are available in differential mode; comedi refers to them as channels 0, 1, 2 and 3, but the hardware documentation refers to them as channels 0, 2, 4 and 6.) In differential mode, the setting of the channel enable bits in the command1 register should depend on whether the scan enable bit is set. Effectively, we need to double the comedi channel number when the scan enable bit is not set in differential mode. The scan enable bit gets set when the AI scan mode is `MODE_MULT_CHAN_UP` or `MODE_MULT_CHAN_DOWN`, and gets cleared when the AI scan mode is `MODE_SINGLE_CHAN` or `MODE_SINGLE_CHAN_INTERVAL`. The existing test for whether the comedi channel number needs to be doubled in differential mode is incorrect in `labpc_ai_cmd()`. This patch corrects the test. Thanks to Tuomas for suggesting the fix. 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_labpc.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/staging/comedi/drivers/ni_labpc.c b/drivers/staging/comedi/drivers/ni_labpc.c
index ab8f37022a3c..9b204b4d1e73 100644
--- a/drivers/staging/comedi/drivers/ni_labpc.c
+++ b/drivers/staging/comedi/drivers/ni_labpc.c
@@ -1241,7 +1241,9 @@ static int labpc_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s)
else
channel = CR_CHAN(cmd->chanlist[0]);
/* munge channel bits for differential / scan disabled mode */
- if (labpc_ai_scan_mode(cmd) != MODE_SINGLE_CHAN && aref == AREF_DIFF)
+ if ((labpc_ai_scan_mode(cmd) == MODE_SINGLE_CHAN ||
+ labpc_ai_scan_mode(cmd) == MODE_SINGLE_CHAN_INTERVAL) &&
+ aref == AREF_DIFF)
channel *= 2;
devpriv->command1_bits |= ADC_CHAN_BITS(channel);
devpriv->command1_bits |= thisboard->ai_range_code[range];