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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>
This commit is contained in:
Amit Shah 2010-09-02 18:47:52 +05:30 committed by Rusty Russell
parent e062013c7d
commit 3eae0adea9
1 changed files with 25 additions and 0 deletions
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25
drivers/char/virtio_console.c
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@ -196,6 +196,9 @@ struct port {
/* 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 @@ out:
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 @@ static const struct file_operations port_fops = {
.write = port_fops_write,
.poll = port_fops_poll,
.release = port_fops_release,
.fasync = port_fops_fasync,
};
/*
@ -1086,6 +1098,12 @@ static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
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 @@ static int add_port(struct ports_device *portdev, u32 id)
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 @@ static void handle_control_message(struct ports_device *portdev,
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:
/*