Hello, Hans
On Tue, 2009-03-24 at 08:06 +0100, Hans Verkuil wrote:
> On Tuesday 24 March 2009 00:14:07 Alexey Klimov wrote:
> > Hello, all
> >
> > ...
> > static int terratec_open(struct file *file)
> > {
> > return 0;
> > }
> >
> > static int terratec_release(struct file *file)
> > {
> > return 0;
> > }
> > ...
> >
> > ...
> >
> > Such code used in many radio-drivers as i understand.
> >
> > Is it good to place this empty and almost empty functions in:
> > (here i see two variants)
> >
> > 1) In header file that be in linux/drivers/media/radio/ directory.
> > Later, we can move some generic/or repeating code in this header.
> >
> > 2) In any v4l header. What header may contain this ?
> >
> > ?
> >
> > For what ? Well, as i understand we can decrease amount of lines and
> > provide this simple generic functions. It's like
> > video_device_release_empty function behaviour. Maybe not only radio
> > drivers can use such vidioc_g_input and vidioc_s_input.
> >
> > Is it worth ?
>
> I don't think it is worth doing this for g/s_input. I think it is useful to
> have them here: it makes it very clear that there is just a single input
> and the overhead in both lines and actual bytes is minimal.
>
> But for the empty open and release functions you could easily handle that in
> v4l2-dev.c: if you leave the open and release callbacks to NULL, then
> v4l2_open and v4l2_release can just return 0. That would be nice.
>
> Regards,
>
> Hans
>
May i ask help with this ?
Hans, should it be looks like:
diff -r 56cf0f1772f7 linux/drivers/media/radio/radio-terratec.c
--- a/linux/drivers/media/radio/radio-terratec.c Mon Mar 23 19:18:34
2009 -0300
+++ b/linux/drivers/media/radio/radio-terratec.c Fri Mar 27 19:32:38
2009 +0300
@@ -333,20 +333,8 @@
return a->index ? -EINVAL : 0;
}
-static int terratec_open(struct file *file)
-{
- return 0;
-}
-
-static int terratec_release(struct file *file)
-{
- return 0;
-}
-
static const struct v4l2_file_operations terratec_fops = {
.owner = THIS_MODULE,
- .open = terratec_open,
- .release = terratec_release,
.ioctl = video_ioctl2,
};
diff -r 56cf0f1772f7 linux/drivers/media/video/v4l2-dev.c
--- a/linux/drivers/media/video/v4l2-dev.c Mon Mar 23 19:18:34 2009 -0300
+++ b/linux/drivers/media/video/v4l2-dev.c Fri Mar 27 19:32:38 2009 +0300
@@ -264,7 +264,10 @@
/* and increase the device refcount */
video_get(vdev);
mutex_unlock(&videodev_lock);
- ret = vdev->fops->open(filp);
+ if (vdev->fops->open == NULL)
+ ret = 0;
+ else
+ ret = vdev->fops->open(filp);
/* decrease the refcount in case of an error */
if (ret)
video_put(vdev);
@@ -275,7 +278,12 @@
static int v4l2_release(struct inode *inode, struct file *filp)
{
struct video_device *vdev = video_devdata(filp);
- int ret = vdev->fops->release(filp);
+ int ret;
+
+ if (vdev->fops->release == NULL)
+ ret = 0;
+ else
+ ret = vdev->fops->release(filp);
/* decrease the refcount unconditionally since the release()
return value is ignored. */
?
Or in v4l2_open function i can check if vdev->fops->open == NULL before
video_get(vdev); (increasing the device refcount), and if it's NULL then
unlock_mutex and return 0 ?
And the same in v4l2_release - just return 0 in the begining of function
in case vdev->fops->release == NULL ?
What approach is better ?
--
Best regards, Klimov Alexey
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