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Commit 66d4da80 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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staging: comedi: comedi_test: simplify time since last AI scan 



The private data structure `struct waveform_private` currently uses
member `last` to remember the time of the last timer interrupt, and the
member `usec_remainder` to keep track of how far into a simulated scan
the interrupt occurred.  Replace these with a single new member
`ai_last_scan_time` that records the time of the last scan.  This
simplifies the calculation of the number of scans to simulate in the
timer routine, `waveform_ai_interrupt()`.

Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Reviewed-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 21ec1bf7

drivers/staging/comedi/drivers/comedi_test.c

+10 −17
Original line number Diff line number Diff line
@@ -62,11 +62,10 @@ enum waveform_state_bits { 
/* Data unique to this driver */

struct waveform_private {

	struct timer_list timer;

	ktime_t last;	/* time last timer interrupt occurred */

	u64 ai_last_scan_time;		/* time of last AI scan in usec */

	unsigned int uvolt_amplitude;	/* waveform amplitude in microvolts */

	unsigned int usec_period;	/* waveform period in microseconds */

	unsigned int usec_current;	/* current time (mod waveform period) */

	unsigned long usec_remainder;	/* usec since last scan */

	unsigned long state_bits;

	unsigned int scan_period;	/* scan period in usec */

	unsigned int convert_period;	/* conversion period in usec */
@@ -184,27 +183,19 @@ static void waveform_ai_interrupt(unsigned long arg) 
	struct comedi_async *async = s->async;

	struct comedi_cmd *cmd = &async->cmd;

	unsigned int i, j;

	/* all times in microsec */

	unsigned long elapsed_time;

	unsigned int num_scans;

	ktime_t now;



	/* check command is still active */

	if (!test_bit(WAVEFORM_AI_RUNNING, &devpriv->state_bits))

		return;



	now = ktime_get();



	elapsed_time = ktime_to_us(ktime_sub(now, devpriv->last));

	devpriv->last = now;

	num_scans =

	    (devpriv->usec_remainder + elapsed_time) / devpriv->scan_period;

	devpriv->usec_remainder =

	    (devpriv->usec_remainder + elapsed_time) % devpriv->scan_period;

	elapsed_time = ktime_to_us(ktime_get()) - devpriv->ai_last_scan_time;

	num_scans = elapsed_time / devpriv->scan_period;



	num_scans = comedi_nscans_left(s, num_scans);

	for (i = 0; i < num_scans; i++) {

		unsigned long scan_remain_period = devpriv->scan_period;

		unsigned int scan_remain_period = devpriv->scan_period;



		for (j = 0; j < cmd->chanlist_len; j++) {

			unsigned short sample;
@@ -219,6 +210,7 @@ static void waveform_ai_interrupt(unsigned long arg) 
			scan_remain_period -= devpriv->convert_period;

		}

		devpriv->usec_current += scan_remain_period;

		devpriv->ai_last_scan_time += devpriv->scan_period;

	}

	if (devpriv->usec_current >= devpriv->usec_period)

		devpriv->usec_current %= devpriv->usec_period;
@@ -337,6 +329,7 @@ static int waveform_ai_cmd(struct comedi_device *dev, 
{

	struct waveform_private *devpriv = dev->private;

	struct comedi_cmd *cmd = &s->async->cmd;

	u64 usec_current;



	if (cmd->flags & CMDF_PRIORITY) {

		dev_err(dev->class_dev,
@@ -356,10 +349,10 @@ static int waveform_ai_cmd(struct comedi_device *dev, 
		devpriv->scan_period = cmd->scan_begin_arg / NSEC_PER_USEC;

	}



	devpriv->last = ktime_get();

	devpriv->usec_current =

		((u32)ktime_to_us(devpriv->last)) % devpriv->usec_period;

	devpriv->usec_remainder = 0;

	devpriv->ai_last_scan_time = ktime_to_us(ktime_get());

	/* Determine time within waveform period. */

	usec_current = devpriv->ai_last_scan_time;

	devpriv->usec_current = do_div(usec_current, devpriv->usec_period);



	devpriv->timer.expires = jiffies + 1;

	/* mark command as active */