From 5cb0a64effe7608d6fd46f5be3106b1b73300621 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Tue, 1 Dec 2020 13:44:45 +0100 Subject: [PATCH] media: v4l2-dev: add EPOLLPRI in v4l2_poll() when dev is unregistered If the V4L2 device was unregistered, then add EPOLLPRI to the poll mask. Otherwise a select() that only waits for exceptions will not wake up. A select() that waits for read and/or write events *will* wake up on an EPOLLERR, but not (for some reason) if it just waits for exceptions. Strangly the epoll functionality will wakeup on EPOLLERR if you just wait for an exception, so in this respect select() and epoll differ. In the end it doesn't really matter, what matters is that polling file handles are woken up on device unregistration. It also improves the code a bit if vdev->fops->poll is NULL: this didn't check for device unregistration. Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/v4l2-dev.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c index 0ddc355..f9cff03 100644 --- a/drivers/media/v4l2-core/v4l2-dev.c +++ b/drivers/media/v4l2-core/v4l2-dev.c @@ -339,12 +339,14 @@ static ssize_t v4l2_write(struct file *filp, const char __user *buf, static __poll_t v4l2_poll(struct file *filp, struct poll_table_struct *poll) { struct video_device *vdev = video_devdata(filp); - __poll_t res = EPOLLERR | EPOLLHUP; + __poll_t res = EPOLLERR | EPOLLHUP | EPOLLPRI; - if (!vdev->fops->poll) - return DEFAULT_POLLMASK; - if (video_is_registered(vdev)) - res = vdev->fops->poll(filp, poll); + if (video_is_registered(vdev)) { + if (!vdev->fops->poll) + res = DEFAULT_POLLMASK; + else + res = vdev->fops->poll(filp, poll); + } if (vdev->dev_debug & V4L2_DEV_DEBUG_POLL) dprintk("%s: poll: %08x\n", video_device_node_name(vdev), res); -- 2.7.4