staging: comedi: comedidev.h: add 'scans_done' member to comedi_async

Introduce a new member to comedi_async to count the number of scans completed.
This member is cleared by comedi_buf_reset() along with the other comedi_async
members. It is incremented in comedi_inc_scan_progress() when the end of scan
is detected.

This member will be used to clean up the scan counting in the comedi drivers.
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>

drivers/staging/comedi/comedi_buf.c

@@ -236,6 +236,7 @@ void comedi_buf_reset(struct comedi_subdevice *s)
 	async->buf_read_ptr = 0;
 
 	async->cur_chan = 0;
+	async->scans_done = 0;
 	async->scan_progress = 0;
 	async->munge_chan = 0;
 	async->munge_count = 0;

drivers/staging/comedi/comedidev.h

@@ -121,6 +121,7 @@ struct comedi_buf_map {
  * @buf_read_ptr:	buffer position for reader
  * @cur_chan:		current position in chanlist for scan (for those
  *			drivers that use it)
+ * @scans_done:		the number of scans completed (COMEDI_CB_EOS)
  * @scan_progress:	amount received or sent for current scan (in bytes)
  * @munge_chan:		current position in chanlist for "munging"
  * @munge_count:	"munge" count (in bytes, modulo 2**32)
@@ -201,6 +202,7 @@ struct comedi_async {
 	unsigned int buf_write_ptr;
 	unsigned int buf_read_ptr;
 	unsigned int cur_chan;
+	unsigned int scans_done;
 	unsigned int scan_progress;
 	unsigned int munge_chan;
 	unsigned int munge_count;

drivers/staging/comedi/drivers.c

@@ -352,6 +352,13 @@ void comedi_inc_scan_progress(struct comedi_subdevice *s,
 
 	async->scan_progress += num_bytes;
 	if (async->scan_progress >= scan_length) {
+		unsigned int nscans = async->scan_progress / scan_length;
+
+		if (async->scans_done < (UINT_MAX - nscans))
+			async->scans_done += nscans;
+		else
+			async->scans_done = UINT_MAX;
+
 		async->scan_progress %= scan_length;
 		async->events |= COMEDI_CB_EOS;
 	}