For write(), any data copied to the data buffer after the previously
set up streaming acquisition command has finished won't be used, but a
non-empty write() does not currently return 0 (or -EPIPE on error) after
the command has finished until the data buffer has been filled up.
Change this behavior to return 0 (or -EPIPE) any time after the command
has finished, without bothering to fill up the buffer with more useless
data.
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
drivers/staging/comedi/comedi_fops.c | 23 +++++++++++++----------
1 files changed, 13 insertions(+), 10 deletions(-)
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 158a6b2..9a26428 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1576,6 +1576,19 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
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;
@@ -1588,16 +1601,6 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
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;
--
1.7.1
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