On Friday 27 March 2009 17:44:05 Alexey Klimov wrote:
> 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 ?
This is simpler:
diff -r 2e0c6ff1bda3 linux/drivers/media/video/v4l2-dev.c
--- a/linux/drivers/media/video/v4l2-dev.c Mon Mar 23 19:01:18 2009
+0100
+++ b/linux/drivers/media/video/v4l2-dev.c Fri Mar 27 17:47:51 2009
+0100
@@ -250,7 +250,7 @@
static int v4l2_open(struct inode *inode, struct file *filp)
{
struct video_device *vdev;
- int ret;
+ int ret = 0;
/* Check if the video device is available */
mutex_lock(&videodev_lock);
@@ -264,7 +264,9 @@
/* and increase the device refcount */
video_get(vdev);
mutex_unlock(&videodev_lock);
- ret = vdev->fops->open(filp);
+ if (vdev->fops->open)
+ ret = vdev->fops->open(filp);
+
/* decrease the refcount in case of an error */
if (ret)
video_put(vdev);
@@ -275,7 +277,10 @@
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 = 0;
+
+ if (vdev->fops->release)
+ ret = vdev->fops->release(filp);
/* decrease the refcount unconditionally since the release()
return value is ignored. */
Regards,
Hans
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG
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