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Staging: comedi: don't write to buffer if command finished

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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@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Ian Abbott 2010-05-19 17:22:41 +01:00 committed by Greg Kroah-Hartman
parent ee4063fa6b
commit d261154057
1 changed files with 13 additions and 10 deletions
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23
drivers/staging/comedi/comedi_fops.c
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@ -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;