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[PATCH 5/8] staging: comedi: COMEDI_BUFINFO: return error if no active command

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The `COMEDI_BUFINFO` ioctl is used to advance the current position in
the buffer and/or get the current buffer position.  If no asynchronous
command is active (started via the file object that issued this ioctl),
this information is meaningless.  Change it to return an error
(`-EINVAL`) in this case.  Prior to this change, if a command was
started via a different file object, the ioctl returned `-EACCES`, but
now it will return `-EINVAL`, which is consistent with the current
behavior of the "read" and "write" file operation handlers.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
---
 drivers/staging/comedi/comedi_fops.c | 22 ++--------------------
 1 file changed, 2 insertions(+), 20 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index b7c9270..a9fabf7 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1123,24 +1123,8 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 
 	async = s->async;
 
-	if (!async) {
-		dev_dbg(dev->class_dev,
-			"subdevice does not have async capability\n");
-		bi.buf_write_ptr = 0;
-		bi.buf_read_ptr = 0;
-		bi.buf_write_count = 0;
-		bi.buf_read_count = 0;
-		bi.bytes_read = 0;
-		bi.bytes_written = 0;
-		goto copyback;
-	}
-	if (!s->busy) {
-		bi.bytes_read = 0;
-		bi.bytes_written = 0;
-		goto copyback_position;
-	}
-	if (s->busy != file)
-		return -EACCES;
+	if (!async || s->busy != file)
+		return -EINVAL;
 
 	if (!(async->cmd.flags & CMDF_WRITE)) {
 		/* command was set up in "read" direction */
@@ -1165,7 +1149,6 @@ static int do_bufinfo_ioctl(struct comedi_device *dev,
 		bi.bytes_read = 0;
 	}
 
-copyback_position:
 	bi.buf_write_count = async->buf_write_count;
 	bi.buf_write_ptr = async->buf_write_ptr;
 	bi.buf_read_count = async->buf_read_count;
@@ -1174,7 +1157,6 @@ copyback_position:
 	if (become_nonbusy)
 		do_become_nonbusy(dev, s);
 
-copyback:
 	if (copy_to_user(arg, &bi, sizeof(bi)))
 		return -EFAULT;
 
-- 
2.7.0

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staging: comedi: COMEDI_BUFINFO: some behavioural changes Ian Abbott <abbotti@mev.co.uk> - 2016-02-19 17:20 +0100
  [PATCH 2/8] staging: comedi: COMEDI_BUFINFO: force bytes_read or bytes_written to 0 Ian Abbott <abbotti@mev.co.uk> - 2016-02-19 17:20 +0100
  [PATCH 5/8] staging: comedi: COMEDI_BUFINFO: return error if no active command Ian Abbott <abbotti@mev.co.uk> - 2016-02-19 17:20 +0100
  [PATCH 8/8] staging: comedi: COMEDI_BUFINFO: terminate "write" command when stopped Ian Abbott <abbotti@mev.co.uk> - 2016-02-19 17:20 +0100
  [PATCH 7/8] staging: comedi: COMEDI_BUFINFO: return -EPIPE for abnormal read Ian Abbott <abbotti@mev.co.uk> - 2016-02-19 17:20 +0100

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