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Staging: comedi: drivers: adl_pci9111: Fix AI commands in TRIG_FOLLOW case

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I received a report that AI streaming acquisitions do not work properly
for the adl_pci9111 driver when convert_src is TRIG_TIMER and
scan_begin_src is TRIG_FOLLOW (and scan_begin_arg is therefore 0).  This
seems to be down to the incorrect setting of dev_private->scan_delay in
pci9111_ai_do_cmd().  Under the previously stated conditions,
dev_private->scan_delay ends up set to (unsigned int)-1, but it ought to
be set to 0.  The function sets it to 0 initially, and it only makes
sense to change it if both convert_src and scan_begin_src are set to
TRIG_TIMER.

Note: 'scan_delay' is the number of unwanted scans to discard after each
valid scan.  The hardware does not support 'scan' timing as such, just a
regularly paced conversion timer (with automatic channel switching
between conversions).  The driver simulates a scan period that is some
(>1) multiple of the conversion period times the scan length
(chanlist_len samples) by reading chanlist_len samples and discarding
the next scan_delay times chanlist_len samples.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Ian Abbott 2010-06-18 12:11:28 +01:00 committed by Greg Kroah-Hartman
parent 44176d9f82
commit 6c2fd30804
1 changed files with 6 additions and 3 deletions
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9
drivers/staging/comedi/drivers/adl_pci9111.c
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@ -824,9 +824,12 @@ static int pci9111_ai_do_cmd(struct comedi_device *dev,
plx9050_interrupt_control(dev_private->lcr_io_base, true, true,
false, true, true);
dev_private->scan_delay =
(async_cmd->scan_begin_arg / (async_cmd->convert_arg *
async_cmd->chanlist_len)) - 1;
if (async_cmd->scan_begin_src == TRIG_TIMER) {
dev_private->scan_delay =
(async_cmd->scan_begin_arg /
(async_cmd->convert_arg *
async_cmd->chanlist_len)) - 1;
}
break;