From 46ef0fac7ac268420316f183c5a67e7fbab1edee Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 14 May 2010 15:29:11 +0000
Subject: [PATCH] For write(), don't bother writing data to buffer if command
 already finished, as the data won't be used anyway.  This allows user code to
 see the command has finished before it has refilled the buffer completely.

---
 comedi/comedi_fops.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/comedi/comedi_fops.c b/comedi/comedi_fops.c
index 9a5e0ea2..a6386675 100644
--- a/comedi/comedi_fops.c
+++ b/comedi/comedi_fops.c
@@ -1580,6 +1580,19 @@ static ssize_t comedi_write(struct file *file, const char *buf, size_t nbytes,
 	while (nbytes > 0 && !retval) {
 		set_current_state(TASK_INTERRUPTIBLE);
 
+		if (!(comedi_get_subdevice_runflags(s) & SRF_RUNNING)) {
+			if (count == 0) {
+				if (comedi_get_subdevice_runflags(s) &
+					SRF_ERROR) {
+					retval = -EPIPE;
+				} else {
+					retval = 0;
+				}
+				do_become_nonbusy(dev, s);
+			}
+			break;
+		}
+
 		n = nbytes;
 
 		m = n;
@@ -1594,16 +1607,6 @@ static ssize_t comedi_write(struct file *file, const char *buf, size_t nbytes,
 			n = m;
 
 		if (n == 0) {
-			if (!(comedi_get_subdevice_runflags(s) & SRF_RUNNING)) {
-				if (comedi_get_subdevice_runflags(s) &
-					SRF_ERROR) {
-					retval = -EPIPE;
-				} else {
-					retval = 0;
-				}
-				do_become_nonbusy(dev, s);
-				break;
-			}
 			if (file->f_flags & O_NONBLOCK) {
 				retval = -EAGAIN;
 				break;
-- 
2.26.2