Re: [PATCH 6/6] V4L: Events: Add documentation

[Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>]

Hans Verkuil wrote:
> On Monday 22 February 2010 23:47:49 Sakari Ailus wrote:
>>>> +Drivers do not initialise events directly. The events are initialised
>>>> +through v4l2_fh_init() if video_device->ioctl_ops->vidioc_subscribe_event is
>>>> +non-NULL. This *MUST* be performed in the driver's
>>>> +v4l2_file_operations->open() handler.
>>>> +
>>>> +Events are delivered to user space through the poll system call. The driver
>>>> +can use v4l2_fh->events->wait wait_queue_head_t as the argument for
>>>> +poll_wait().
>>>> +
>>>> +There are standard and private events. New standard events must use the
>>>> +smallest available event type. The drivers must allocate their events
>>>> +starting from base (V4L2_EVENT_PRIVATE_START + n * 1024) while individual
>>>> +events start from base + 1.
>>>
>>> What do you mean with 'while individual events start from base + 1'? I still
>>> don't understand that phrase.
>>
>> Will be "There are standard and private events. New standard events must
>> use the smallest available event type. The drivers must allocate their
>> events starting from base (V4L2_EVENT_PRIVATE_START + n * 1024) + 1." in
>> the next one.
> 
> Ah, OK. But why '+ 1'? I don't really see a reason for that to be honest.
> Am I missing something?

Many V4L2 control classes do that. No other reason really. :-) Can be
removed on my behalf.

-- 
Sakari Ailus
sakari.ailus@maxwell.research.nokia.com