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@xxxxxxxxx>
---
drivers/staging/comedi/comedi_fops.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 9505a34..db88fa5 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2477,8 +2477,12 @@ 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;
@@ -2516,6 +2520,7 @@ 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) {
--
2.6.1
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