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staging: comedi: return error on "read" if no command set up

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The "read" file operation handler, `comedi_read()` returns an error for
pretty much any condition that prevents a "read" going ahead.  One of
the conditions that prevents a "read" going ahead is that no
asynchronous command has been set up, but that currently results in a
return value of 0 (unless COMEDI instructions are being processed or an
asynchronous command has been set up by a different file object).
Change it to return `-EINVAL` in this case.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2015-10-12 17:21:27 +01:00 committed by Greg Kroah-Hartman
parent f84e27adfc
commit a8ed75c083
1 changed files with 6 additions and 1 deletions
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7
drivers/staging/comedi/comedi_fops.c
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@ -2478,8 +2478,12 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
}
async = s->async;
if (!s->busy || !nbytes)
if (!nbytes)
goto out;
if (!s->busy) {
retval = -EINVAL;
goto out;
}
if (s->busy != file) {
retval = -EACCES;
goto out;
@ -2517,6 +2521,7 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes,
break;
}
if (!s->busy) {
retval = -EINVAL;
break;
}
if (s->busy != file) {