Hi Hans,
On 04/22/14 18:22, Hans Verkuil wrote:
> On 04/21/2014 11:26 AM, Arun Kumar K wrote:
>> From: Pawel Osciak <posciak@xxxxxxxxxxxx>
>>
>> This event indicates that the decoder has reached a point in the stream,
>> at which the resolution changes. The userspace is expected to provide a new
>> set of CAPTURE buffers for the new format before decoding can continue.
>> The event can also be used for more generic events involving resolution
>> or format changes at runtime for all kinds of video devices.
>>
>> Signed-off-by: Pawel Osciak <posciak@xxxxxxxxxxxx>
>> Signed-off-by: Arun Kumar K <arun.kk@xxxxxxxxxxx>
>> ---
>> .../DocBook/media/v4l/vidioc-subscribe-event.xml | 16 ++++++++++++++++
>> include/uapi/linux/videodev2.h | 6 ++++++
>> 2 files changed, 22 insertions(+)
>>
>> diff --git a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
>> index 5c70b61..0aec831 100644
>> --- a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
>> +++ b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
>> @@ -155,6 +155,22 @@
>> </entry>
>> </row>
>> <row>
>> + <entry><constant>V4L2_EVENT_SOURCE_CHANGE</constant></entry>
>> + <entry>5</entry>
>> + <entry>
>> + <para>This event is triggered when a resolution or format change
>> + is detected during runtime by the video device. It can be a
>> + runtime resolution change triggered by a video decoder or the
>> + format change happening on an HDMI connector. Application may
>> + need to reinitialize buffers before proceeding further.</para>
>> +
>> + <para>This event has a &v4l2-event-source-change; associated
>> + with it. This has significance only for v4l2 subdevs where the
>> + <structfield>pad_num</structfield> field will be updated with
>> + the pad number on which the event is triggered.</para>
>> + </entry>
>> + </row>
>> + <row>
>> <entry><constant>V4L2_EVENT_PRIVATE_START</constant></entry>
>> <entry>0x08000000</entry>
>> <entry>Base event number for driver-private events.</entry>
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 6ae7bbe..12e0614 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -1733,6 +1733,7 @@ struct v4l2_streamparm {
>> #define V4L2_EVENT_EOS 2
>> #define V4L2_EVENT_CTRL 3
>> #define V4L2_EVENT_FRAME_SYNC 4
>> +#define V4L2_EVENT_SOURCE_CHANGE 5
>> #define V4L2_EVENT_PRIVATE_START 0x08000000
>>
>> /* Payload for V4L2_EVENT_VSYNC */
>> @@ -1764,12 +1765,17 @@ struct v4l2_event_frame_sync {
>> __u32 frame_sequence;
>> };
>>
>> +struct v4l2_event_source_change {
>> + __u32 pad_num;
>> +};
>> +
>> struct v4l2_event {
>> __u32 type;
>> union {
>> struct v4l2_event_vsync vsync;
>> struct v4l2_event_ctrl ctrl;
>> struct v4l2_event_frame_sync frame_sync;
>> + struct v4l2_event_source_change source_change;
>> __u8 data[64];
>> } u;
>> __u32 pending;
>>
>
> This needs to be done differently. The problem is that you really have multiple
> events that you want to subscribe to: one for each pad (or input: see the way
> VIDIOC_G/S_EDID maps pad to an input or output index when used with a video node,
> we have to support that for this event as well).
>
> What you want to do is similar to what is done for control events: there you can
> subscribe for a specific control and get notified when that control changes.
>
> The way that works in the event code is that the 'id' field in the v4l2_event
> struct contains that control ID, or, in this case, the pad/input/output index.
>
As I am new to v4l2-events itself, I might have some noob questions.
I understood filling pad index into id field. But for video nodes,
the application is supposed to put v4l2_buf_type in the id field?
> In the application you will subscribe to the SOURCE_CHANGE event for a specific
> pad/input/output index.
>
> In other words, the pad_num field should be dropped and the id field used
> instead.
>
> Assuming we will also add a 'changes' field (see my reply to the other post
> on that topic), then you should also provide replace and merge ops (see
> v4l2-ctrls.c). That way it is sufficient to use just one element when calling
> v4l2_event_subscribe(): you will never loose information since if multiple
> events arrive before the application can dequeue them, the 'changes' information
> will be the ORed value of all those intermediate events.
>
If I understand correctly, the implementation should go somewhat in the
following lines:
+void v4l2_event_src_replace(struct v4l2_event *old, const struct
v4l2_event *new)
+{
+ u32 old_changes = old->u.src_change.changes;
+
+ old->u.src_change = new->u.src_change;
+ old->u.src_change.changes |= old_changes;
+}
+
+void v4l2_event_src_merge(const struct v4l2_event *old, struct
v4l2_event *new)
+{
+ new->u.src_change.changes |= old->u.src_change.changes;
+}
+
+const struct v4l2_subscribed_event_ops v4l2_event_src_ch_ops = {
+ .replace = v4l2_event_src_replace,
+ .merge = v4l2_event_src_merge,
+};
+
+int v4l2_src_change_event_subscribe(struct v4l2_fh *fh,
+ const struct v4l2_event_subscription *sub)
+{
+ if (sub->type == V4L2_EVENT_SOURCE_CHANGE)
+ return v4l2_event_subscribe(fh, sub, 0,
&v4l2_event_src_ch_ops);
+ return -EINVAL;
+}
And v4l2-event.c is the right place to put it?
And in the videodev2.h file:
+#define V4L2_EVENT_SRC_CH_RESOLUTION (1 << 0)
+#define V4L2_EVENT_SRC_CH_FORMAT (1 << 1)
+
+struct v4l2_event_src_change {
+ __u32 changes;
+};
+
struct v4l2_event {
__u32 type;
union {
struct v4l2_event_vsync vsync;
struct v4l2_event_ctrl ctrl;
struct v4l2_event_frame_sync frame_sync;
+ struct v4l2_event_src_change src_change;
__u8 data[64];
} u;
__u32 pending;
Please correct me if my understanding is totally wrong here?
Regards
Arun
> It's all more work, but it is critical to ensure that the application never
> misses events.
>
> Regards,
>
> Hans
>
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