[GIT,PATCHES,FOR,3.1] v4l-dvb: add and use poll_requested_events() function

From: Hans Verkuil <hans.verkuil@cisco.com>

Em 17-07-2011 08:19, Hans Verkuil escreveu:
> Hi Mauro,
> 
> This patch series adds the poll_requested_events() function and uses it in
> the V4L2 core and the ivtv driver.
> 
> The poll patch is unchanged from the RFCv3 patch posted a week ago and the
> other patches are unchanged from the RFCv1 patch series posted last Wednesday
> on the linux-media list.
> 
> Tested with vivi and ivtv.
> 
> Regards,
> 
> 	Hans
> 
> The following changes since commit bec969c908bb22931fd5ab8ecdf99de8702a6a31:
> 
>   [media] v4l: s5p-tv: add TV Mixer driver for Samsung S5P platform (2011-07-14 13:09:48 -0300)
> 
> are available in the git repository at:
>   ssh://linuxtv.org/git/hverkuil/media_tree.git poll
> 
> Hans Verkuil (6):
>       poll: add poll_requested_events() function
>       ivtv: only start streaming in poll() if polling for input.
>       videobuf2: only start streaming in poll() if so requested by the poll mask.
>       videobuf: only start streaming in poll() if so requested by the poll mask.
>       videobuf2-core: also test for pending events.
>       vivi: let vb2_poll handle events.
> 
>  drivers/media/video/ivtv/ivtv-fileops.c |    6 ++-
>  drivers/media/video/videobuf-core.c     |    3 +-
>  drivers/media/video/videobuf2-core.c    |   48 +++++++++++++++++++++---------
>  drivers/media/video/vivi.c              |    9 +-----
>  fs/eventpoll.c                          |   19 +++++++++--
>  fs/select.c                             |   38 +++++++++++-------------
>  include/linux/poll.h                    |    7 ++++-
>  7 files changed, 78 insertions(+), 52 deletions(-)
> --
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I don't like the idea of merging the first patch directly on my tree, without
the vfs maintainer ack.

The better would be if Alexander could merge it, or give his ack on it.
Alternatively, if he is not maintaining it anymore, then maybe Andrew
can help us.

Thanks!
Mauro

-

From: Hans Verkuil <hans.verkuil@cisco.com>
Subject: poll: add poll_requested_events() function

In some cases the poll() implementation in a driver has to do different
things depending on the events the caller wants to poll for. An example is
when a driver needs to start a DMA engine if the caller polls for POLLIN,
but doesn't want to do that if POLLIN is not requested but instead only
POLLOUT or POLLPRI is requested. This is something that can happen in the
video4linux subsystem.

Unfortunately, the current epoll/poll/select implementation doesn't provide
that information reliably. The poll_table_struct does have it: it has a key
field with the event mask. But once a poll() call matches one or more bits
of that mask any following poll() calls are passed a NULL poll_table_struct
pointer.

The solution is to set the qproc field to NULL in poll_table_struct once
poll() matches the events, not the poll_table_struct pointer itself. That
way drivers can obtain the mask through a new poll_requested_events inline.

The poll_table_struct can still be NULL since some kernel code calls it
internally (netfs_state_poll() in ./drivers/staging/pohmelfs/netfs.h). In
that case poll_requested_events() returns ~0 (i.e. all events).

Since eventpoll always leaves the key field at ~0 instead of using the
requested events mask, that source was changed as well to properly fill in
the key field.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
---
 fs/eventpoll.c       |   19 +++++++++++++++----
 fs/select.c          |   38 +++++++++++++++++---------------------
 include/linux/poll.h |    7 ++++++-
 3 files changed, 38 insertions(+), 26 deletions(-)

[GIT,PATCHES,FOR,3.1] v4l-dvb: add and use poll_requested_events() function

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