virtio: console: Send SIGIO to processes that request it for host events
A process can request for SIGIO on host connect / disconnect events
using the O_ASYNC file flag using fcntl().
If that's requested, and if the guest-side connection for the port is
open, any host-side open/close events for that port will raise a SIGIO.
The process can then use poll() within the signal handler to find out
which port triggered the signal.
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c84486b..c4ca436 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -196,6 +196,9 @@
/* The 'name' of the port that we expose via sysfs properties */
char *name;
+ /* We can notify apps of host connect / disconnect events via SIGIO */
+ struct fasync_struct *async_queue;
+
/* The 'id' to identify the port with the Host */
u32 id;
@@ -815,6 +818,14 @@
return ret;
}
+static int port_fops_fasync(int fd, struct file *filp, int mode)
+{
+ struct port *port;
+
+ port = filp->private_data;
+ return fasync_helper(fd, filp, mode, &port->async_queue);
+}
+
/*
* The file operations that we support: programs in the guest can open
* a console device, read from it, write to it, poll for data and
@@ -828,6 +839,7 @@
.write = port_fops_write,
.poll = port_fops_poll,
.release = port_fops_release,
+ .fasync = port_fops_fasync,
};
/*
@@ -1086,6 +1098,12 @@
return nr_added_bufs;
}
+static void send_sigio_to_port(struct port *port)
+{
+ if (port->async_queue && port->guest_connected)
+ kill_fasync(&port->async_queue, SIGIO, POLL_OUT);
+}
+
static int add_port(struct ports_device *portdev, u32 id)
{
char debugfs_name[16];
@@ -1108,6 +1126,7 @@
port->name = NULL;
port->inbuf = NULL;
port->cons.hvc = NULL;
+ port->async_queue = NULL;
port->cons.ws.ws_row = port->cons.ws.ws_col = 0;
@@ -1362,6 +1381,12 @@
spin_lock_irq(&port->outvq_lock);
reclaim_consumed_buffers(port);
spin_unlock_irq(&port->outvq_lock);
+
+ /*
+ * If the guest is connected, it'll be interested in
+ * knowing the host connection state changed.
+ */
+ send_sigio_to_port(port);
break;
case VIRTIO_CONSOLE_PORT_NAME:
/*