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Commit a2706b09 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: das1800: clarify the analog input cmd triggers 



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: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5f657f8b

drivers/staging/comedi/drivers/das1800.c

+25 −11
Original line number Diff line number Diff line
@@ -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;