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Commit d2611540 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman
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Staging: comedi: don't write to buffer if command finished 



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: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent ee4063fa

drivers/staging/comedi/comedi_fops.c

+13 −10
Original line number Diff line number Diff line
@@ -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;