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v4l2: v4l2_compat: Add eventfd signaling to support polling

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To support polling, we need to be able to signal when data is
available to be read (POLLIN), as well as events (POLLPRI). Add the
necessary calls to eventfd to allow signaling POLLIN. We signal POLLIN
by writing writing to the eventfd, and clear it by reading from the
eventfd, upon VIDIOC_DQBUF.

Note that eventfd does not support signaling POLLPRI, so we don't yet
support V4L2 events.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
This commit is contained in:
Paul Elder 2020-06-04 18:13:52 +09:00
parent 5c5481911a
commit 8df593841d
5 changed files with 32 additions and 1 deletions
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7
src/v4l2/v4l2_compat_manager.cpp
View file

@ -155,12 +155,17 @@ int V4L2CompatManager::openat(int dirfd, const char *path, int oflag, mode_t mod
if (ret < 0)
return ret;
int efd = eventfd(0, oflag & (O_CLOEXEC | O_NONBLOCK));
int efd = eventfd(0, EFD_SEMAPHORE |
((oflag & O_CLOEXEC) ? EFD_CLOEXEC : 0) |
((oflag & O_NONBLOCK) ? EFD_NONBLOCK : 0));
if (efd < 0) {
int err = errno;
proxy->close();
errno = err;
return efd;
}
proxy->bind(efd);
devices_.emplace(efd, proxy);
return efd;