On Tuesday 24 March 2009 08:06:39 Hans Verkuil wrote:
> On Tuesday 24 March 2009 00:14:07 Alexey Klimov wrote:
> > Hello, all
> >
> > After last convertion of radio drivers to use v4l2_device we have such
> > code in many radio drivers:
> > (it's radio-terratec.c for example)
> >
> > ...
> > static int terratec_open(struct file *file)
> > {
> > return 0;
> > }
> >
> > static int terratec_release(struct file *file)
> > {
> > return 0;
> > }
> > ...
> >
> > and
> >
> > ...
> > static int vidioc_g_input(struct file *filp, void *priv, unsigned int
> > *i)
> > {
> > *i = 0;
> > return 0;
> > }
> >
> > static int vidioc_s_input(struct file *filp, void *priv, unsigned int i)
> > {
> > return i ? -EINVAL : 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.
What about making that the default NULL g_input/s_input callbacks handling in
video_ioctl2 ? Devices with a single input wouldn't need to define
g_input/s_input callbacks at all.
> 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,
Laurent Pinchart
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