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staging: comedi: das1800: clarify the analog input cmd triggers

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Clarify the documentation in the comedi driver comment block to
better explain the cmd triggert.

Add a comment to step 2b of the (*do_cmdtest) to clarify the
trigger check.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
H Hartley Sweeten
2016-04-08 12:42:04 -07:00
committed by Greg Kroah-Hartman
parent 5f657f8bf3
commit a2706b0943
1 changed files with 25 additions and 11 deletions
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36
drivers/staging/comedi/drivers/das1800.c
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@@ -39,19 +39,32 @@
* [3] - DMA1 (optional, requires irq and dma0)
*
* analog input cmd triggers supported:
* start_src: TRIG_NOW | TRIG_EXT
* scan_begin_src: TRIG_FOLLOW | TRIG_TIMER | TRIG_EXT
* scan_end_src: TRIG_COUNT
* convert_src: TRIG_TIMER | TRIG_EXT
* (TRIG_EXT requires scan_begin_src == TRIG_FOLLOW)
* stop_src: TRIG_COUNT | TRIG_EXT | TRIG_NONE
*
* scan_begin_src triggers TRIG_TIMER and TRIG_EXT use the card's
* 'burst mode' which limits the valid conversion time to 64 microseconds
* (convert_arg <= 64000). This limitation does not apply if scan_begin_src
* is TRIG_FOLLOW.
* start_src TRIG_NOW command starts immediately
* TRIG_EXT command starts on external pin TGIN
*
* The maximum conversion speeds are not always achievable depending on the
* scan_begin_src TRIG_FOLLOW paced/external scans start immediately
* TRIG_TIMER burst scans start periodically
* TRIG_EXT burst scans start on external pin XPCLK
*
* scan_end_src TRIG_COUNT scan ends after last channel
*
* convert_src TRIG_TIMER paced/burst conversions are timed
* TRIG_EXT conversions on external pin XPCLK
* (requires scan_begin_src == TRIG_FOLLOW)
*
* stop_src TRIG_COUNT command stops after stop_arg scans
* TRIG_EXT command stops on external pin TGIN
* TRIG_NONE command runs until canceled
*
* If TRIG_EXT is used for both the start_src and stop_src, the first TGIN
* trigger starts the command, and the second trigger will stop it. If only
* one is TRIG_EXT, the first trigger will either stop or start the command.
*
* Minimum conversion speed is limited to 64 microseconds (convert_arg <= 64000)
* for 'burst' scans. This limitation does not apply for 'paced' scans. The
* maximum conversion speed is limited by the board (convert_arg >= ai_speed).
* Maximum conversion speeds are not always achievable depending on the
* board setup (see user manual).
*
* NOTES:
@@ -653,6 +666,7 @@ static int das1800_ai_cmdtest(struct comedi_device *dev,
/* Step 2b : and mutually compatible */
/* burst scans must use timed conversions */
if (cmd->scan_begin_src != TRIG_FOLLOW &&
cmd->convert_src != TRIG_TIMER)
err |= -EINVAL;