From abbotti@mev.co.uk Tue Jun 1 13:22:33 2010 From: Ian Abbott Date: Wed, 19 May 2010 17:22:41 +0100 Subject: Staging: comedi: don't write to buffer if command finished Cc: Greg Kroah-Hartman , Frank Mori Hess , Ian Abbott Message-ID: <1274286161-14666-1-git-send-email-abbotti@mev.co.uk> 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 Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) --- 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 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 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;