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Subject[PATCH 6/8] staging: comedi: return error on "write" if no command set up
Date
The "write" file operation handler, `comedi_write()` returns an error
for pretty much any condition that prevents a "write" going ahead. One
of the conditions that prevents a "write" 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>
---
drivers/staging/comedi/comedi_fops.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 4dd4289..2a2b5a0 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2331,9 +2331,12 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
}

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;
@@ -2373,8 +2376,10 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
retval = -ERESTARTSYS;
break;
}
- if (!s->busy)
+ if (!s->busy) {
+ retval = -EINVAL;
break;
+ }
if (s->busy != file) {
retval = -EACCES;
break;
--
2.6.2


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