Re: [PATCH] V4L: Drop meaningless video_is_registered() call in v4l2_open()

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Hans,

On Monday 09 September 2013 11:07:43 Hans Verkuil wrote:
> On 09/06/2013 12:33 AM, Sylwester Nawrocki wrote:
> > On 08/07/2013 07:49 PM, Hans Verkuil wrote:
> >> On 08/07/2013 06:49 PM, Sylwester Nawrocki wrote:
> >>> On 08/02/2013 03:00 PM, Hans Verkuil wrote:
> >>>> On 08/02/2013 02:27 PM, Sylwester Nawrocki wrote:

[snip]

> > The main issue as I see it is that we need to track both driver remove()
> > and struct device .release() calls and free resources only when last of
> > them executes. Data structures which are referenced in fops must not be
> > freed in remove() and we cannot use dev_get_drvdata() in fops, e.g. not
> > protected with device_lock().
> 
> You can do all that by returning 0 if probe() was partially successful (i.e.
> one or more, but not all, nodes were created successfully) by doing what I
> described above. I don't see another way that doesn't introduce a race
> condition.

But isn't this just plain wrong ? If probing fails, I don't see how returning 
success could be a good idea.

> That doesn't mean that there isn't one, it's just that I don't know of a
> better way of doing this.

We might need support from the device core.

-- 
Regards,

Laurent Pinchart