From be611a1de3989bd03a09ae9fbfbacf19072169af Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 19 Feb 2016 16:13:57 +0000
Subject: staging: comedi: COMEDI_BUFINFO: terminate "write" command when
 stopped

The `COMEDI_BUFINFO` ioctl is used to advance the current position in
the buffer by a specified amount (which can be 0) and get the current
position.  An asynchronous command in the "read" direction is terminated
automatically once it has stopped and information about the final
position and error has been reported back to the user.  That is not
currently done for commands in the "write" direction.  Change it to
terminate the command in the "write" direction automatically.  If the
command stopped with an error, report an `EPIPE` error back to the user,
otherwise just report the final buffer position back to the user.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 7cb1d06..d1cf6a1 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1121,6 +1121,7 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 	if (!async || s->busy != file)
 		return -EINVAL;
 
+	runflags = comedi_get_subdevice_runflags(s);
 	if (!(async->cmd.flags & CMDF_WRITE)) {
 		/* command was set up in "read" direction */
 		if (bi.bytes_read) {
@@ -1132,7 +1133,6 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 		 * {"read" position not updated or command stopped normally},
 		 * then become non-busy.
 		 */
-		runflags = comedi_get_subdevice_runflags(s);
 		if (comedi_buf_read_n_available(s) == 0 &&
 		    !comedi_is_runflags_running(runflags) &&
 		    (bi.bytes_read == 0 ||
@@ -1144,9 +1144,12 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 		bi.bytes_written = 0;
 	} else {
 		/* command was set up in "write" direction */
-		if (!comedi_is_subdevice_running(s))
+		if (!comedi_is_runflags_running(runflags)) {
 			bi.bytes_written = 0;
-		if (bi.bytes_written) {
+			become_nonbusy = true;
+			if (comedi_is_runflags_in_error(runflags))
+				retval = -EPIPE;
+		} else if (bi.bytes_written) {
 			comedi_buf_write_alloc(s, bi.bytes_written);
 			bi.bytes_written =
 			    comedi_buf_write_free(s, bi.bytes_written);
-- 
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