On 08/26/2011 05:09 PM, Laurent Pinchart wrote:
Hi Laurent,
Hi Tomasz,
On Friday 26 August 2011 15:06:06 Tomasz Stanislawski wrote:
This patch fix the handling of data passed to V4L2 ioctls. The content of
the structures is not copied if the ioctl fails. It blocks ability to
obtain any information about occurred error other then errno code. This
patch fix this issue.
Does the V4L2 spec say anything on this topic ? We might have applications
that rely on the ioctl argument structure not being touched when a failure
occurs.
Ups.. I missed something. It looks that modifying ioctl content is
illegal if ioctl fails. The spec says:
"When an ioctl that takes an output or read/write parameter fails, the
parameter remains unmodified." (v4l2 ioctl section)
However, there is probably a bug already present in V4L2 framework.
There are some ioctls that takes a pointer to an array as a field in the
argument struct.
The examples are all VIDIOC_*_EXT_CTRLS and VIDIOC_{QUERY/DQ/Q}_BUF family.
The content of such an auxiliary arays is copied even if ioctl fails.
Please take a look to video_usercopy function in v4l2-ioctl.c. Therefore
I think that the spec is already violated. What is your opinion about
this problem?
Now back to selection case.
This patch was added as proposition of fix to VIDIOC_S_SELECTION, to
return the best-hit rectangle if constraints could not be satisfied. The
ioctl return -ERANGE in this case. Using those return values the
application gets some feedback
on loosing constraints.
I could remove rectangle returning from the spec and s5p-tv code for now.
Regards,
Tomasz Stanislawski
Signed-off-by: Tomasz Stanislawski<t.stanislaws@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park<kyungmin.park@xxxxxxxxxxx>
---
drivers/media/video/v4l2-ioctl.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)
diff --git a/drivers/media/video/v4l2-ioctl.c
b/drivers/media/video/v4l2-ioctl.c index 543405b..9f54114 100644
--- a/drivers/media/video/v4l2-ioctl.c
+++ b/drivers/media/video/v4l2-ioctl.c
@@ -2490,8 +2490,6 @@ video_usercopy(struct file *file, unsigned int cmd,
unsigned long arg, err = -EFAULT;
goto out_array_args;
}
- if (err< 0)
- goto out;
out_array_args:
/* Copy results into user buffer */
--
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