staging: comedi: drivers: move comedi_async 'cur_chan' tracking into the core

The commedi_async 'cur_chan' member is used to track the current position
in the chanlist for a scan. Currently only a couple comedi drivers use
this member.

For aeshtetics, move the 'cur_chan' tracking into the core for non-SDF_PACKED
subdevices. The 'cur_chan' will be updated after reading or writing samples
to the async buffer by comedi_inc_scan_progress(). All non-SDF_PACKED subdevices
will then automatiaclly track the 'cur_chan'.

Some of the drivers use the 'cur_chan' to detect the end of scan event when
counting scans. The COMEDI_CB_EOS event is automatically added by the core
when the end of scan is detected. The drivers just need to check if the
'cur_chan' is 0 to count the number of scans completed.

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>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index ff2df85..9c55dc7 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -341,8 +341,15 @@ void comedi_inc_scan_progress(struct comedi_subdevice *s,
 			      unsigned int num_bytes)
 {
 	struct comedi_async *async = s->async;
+	struct comedi_cmd *cmd = &async->cmd;
 	unsigned int scan_length = comedi_bytes_per_scan(s);
 
+	/* track the 'cur_chan' for non-SDF_PACKED subdevices */
+	if (!(s->subdev_flags & SDF_PACKED)) {
+		async->cur_chan += comedi_bytes_to_samples(s, num_bytes);
+		async->cur_chan %= cmd->chanlist_len;
+	}
+
 	async->scan_progress += num_bytes;
 	if (async->scan_progress >= scan_length) {
 		async->scan_progress %= scan_length;