linux-kernel - [PATCH 4/6] staging: comedi: usbduxsigma: round down AI scan_begin

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Message-Id: <1437666422-25222-5-git-send-email-abbotti@mev.co.uk>
Date:	Thu, 23 Jul 2015 16:47:00 +0100
From:	Ian Abbott <abbotti@....co.uk>
To:	<driverdev-devel@...uxdriverproject.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Abbott <abbotti@....co.uk>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	Bernd Porr <mail@...ndporr.me.uk>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 4/6] staging: comedi: usbduxsigma: round down AI scan_begin_arg at step 4.

The return value of the `cmdtest` handler for a subdevice checks the
prospective new command in various steps and returns the step number at
which any problem was detected, or 0 if no problem was detected.  It is
allowed to modify the command in various ways at each step.  Corrections
for out-of-range values are generally made at step 3, and minor
adjustments such as rounding are generally made at step 4.

The `cmdtest` handler for the AI subdevice (`usbduxsigma_ai_cmdtest()`)
currently modifies `cmd->scan_begin_arg` to bring it into range and
round it down at step 3.  Move the rounding down part to step 4 to
follow the usual Comedi convention.

Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
 drivers/staging/comedi/drivers/usbduxsigma.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/staging/comedi/drivers/usbduxsigma.c b/drivers/staging/comedi/drivers/usbduxsigma.c
index 65a0df4..4655048 100644
--- a/drivers/staging/comedi/drivers/usbduxsigma.c
+++ b/drivers/staging/comedi/drivers/usbduxsigma.c
@@ -518,17 +518,12 @@ static int usbduxsigma_ai_cmdtest(struct comedi_device *dev,
 		 */
 		err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
 						    (125000 * interval));
-
-		tmp = (cmd->scan_begin_arg / 125000) * 125000;
 	} else {
 		/* full speed */
 		/* 1kHz scans every USB frame */
 		err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
 						    1000000);
-
-		tmp = (cmd->scan_begin_arg / 1000000) * 1000000;
 	}
-	err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, tmp);
 
 	err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
 					   cmd->chanlist_len);
@@ -541,6 +536,14 @@ static int usbduxsigma_ai_cmdtest(struct comedi_device *dev,
 	if (err)
 		return 3;
 
+	/* Step 4: fix up any arguments */
+
+	tmp = rounddown(cmd->scan_begin_arg, high_speed ? 125000 : 1000000);
+	err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, tmp);
+
+	if (err)
+		return 4;
+
 	return 0;
 }
 
-- 
2.1.4

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