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[PATCH 6/8] staging: comedi: return error on "write" if no command set up

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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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[PATCH 0/8] staging: comedi: some comedi_write() changes Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
  [PATCH 1/8] staging: comedi: rearrange comedi_write() code Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
    RE: [PATCH 1/8] staging: comedi: rearrange comedi_write() code Hartley Sweeten <HartleyS@visionengravers.com> - 2015-11-19 18:10 +0100
  [PATCH 5/8] staging: comedi: allow buffer wraparound in comedi_write() Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
  [PATCH 8/8] staging: comedi: check for more errors for zero-length write Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
  [PATCH 4/8] staging: comedi: avoid bad truncation of a size_t in comedi_write() Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
  [PATCH 6/8] staging: comedi: return error on "write" if no command set up Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
  [PATCH 7/8] staging: comedi: simplify returned errors for comedi_write() Ian Abbott <abbotti@mev.co.uk> - 2015-11-18 19:00 +0100
  RE: [PATCH 0/8] staging: comedi: some comedi_write() changes Hartley Sweeten <HartleyS@visionengravers.com> - 2015-11-19 18:40 +0100

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