Allow guest userspace applications to open, read from, write to, poll
the ports via the char dev interface.
When a port gets opened, a notification is sent to the host via a
control message indicating a connection has been established. Similarly,
on closing of the port, a notification is sent indicating disconnection.
Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
---
drivers/char/virtio_console.c | 165 ++++++++++++++++++++++++++++++++++++++--
include/linux/virtio_console.h | 3 +
2 files changed, 161 insertions(+), 7 deletions(-)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 4d55f0f..66875d6 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -19,11 +19,15 @@
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/err.h>
+#include <linux/fs.h>
#include <linux/init.h>
#include <linux/list.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/virtio.h>
#include <linux/virtio_console.h>
+#include <linux/wait.h>
#include <linux/workqueue.h>
#include "hvc_console.h"
@@ -146,6 +150,9 @@ struct port {
*/
spinlock_t readbuf_list_lock;
+ /* A waitqueue for poll() or blocking read operations */
+ wait_queue_head_t waitqueue;
+
/* Each port associates with a separate char device */
struct cdev cdev;
struct device *dev;
@@ -158,6 +165,9 @@ struct port {
/* The 'id' to identify the port with the Host */
u32 id;
+
+ /* Is the host device open */
+ bool host_connected;
};
/* This is the very early arch-specified put chars function. */
@@ -245,7 +255,7 @@ static ssize_t send_buf(struct port *port, const char *in_buf, size_t in_count,
return 0;
header.id = port->id;
- header.flags = flags;
+ header.flags = flags | VIRTIO_CONSOLE_HDR_START_DATA;
header_len = use_multiport(port->portdev) ? sizeof(header) : 0;
in_offset = 0; /* offset in the user buffer */
@@ -261,10 +271,7 @@ static ssize_t send_buf(struct port *port, const char *in_buf, size_t in_count,
list_del(&buf->list);
spin_unlock_irqrestore(&port->portdev->write_list_lock, irqf);
- if (header_len) {
- memcpy(buf->buf, &header, header_len);
- copy_size -= header_len;
- }
+ copy_size -= header_len;
if (from_user) {
ret = copy_from_user(buf->buf + header_len,
in_buf + in_offset, copy_size);
@@ -280,8 +287,13 @@ static ssize_t send_buf(struct port *port, const char *in_buf, size_t in_count,
ret = 0; /* Emulate copy_from_user behaviour */
}
buf->len = header_len + copy_size - ret;
- sg_init_one(sg, buf->buf, buf->len);
+ if (!(in_count - in_offset - (buf->len - header_len)))
+ header.flags |= VIRTIO_CONSOLE_HDR_END_DATA;
+ if (header_len)
+ memcpy(buf->buf, &header, header_len);
+
+ sg_init_one(sg, buf->buf, buf->len);
spin_lock_irqsave(&port->portdev->write_list_lock, irqf);
ret = out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, buf);
if (ret < 0) {
@@ -292,6 +304,9 @@ static ssize_t send_buf(struct port *port, const char *in_buf, size_t in_count,
}
in_offset += buf->len - header_len;
+ /* Set the START_DATA flag only for the first buffer. */
+ header.flags &= ~VIRTIO_CONSOLE_HDR_START_DATA;
+
/* No space left in the vq anyway */
if (!ret)
break;
@@ -372,6 +387,129 @@ static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
return out_offset;
}
+/* The condition that must be true for polling to end */
+static bool wait_is_over(struct port *port)
+{
+ return !list_empty(&port->readbuf_head) || !port->host_connected;
+}
+
+static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
+ size_t count, loff_t *offp)
+{
+ struct port *port;
+ ssize_t ret;
+
+ port = filp->private_data;
+
+ if (list_empty(&port->readbuf_head)) {
+ /*
+ * If nothing's connected on the host just return 0 in
+ * case of list_empty; this tells the userspace app
+ * that there's no connection
+ */
+ if (!port->host_connected)
+ return 0;
+ if (filp->f_flags & O_NONBLOCK)
+ return -EAGAIN;
+
+ ret = wait_event_interruptible(port->waitqueue,
+ wait_is_over(port));
+ if (ret < 0)
+ return ret;
+ }
+ /*
+ * We could've received a disconnection message while we were
+ * waiting for more data.
+ *
+ * This check is not clubbed in the if() statement above as we
+ * might receive some data as well as the host could get
+ * disconnected after we got woken up from our wait. So we
+ * really want to give off whatever data we have and only then
+ * check for host_connected.
+ */
+ if (list_empty(&port->readbuf_head) && !port->host_connected)
+ return 0;
+
+ return fill_readbuf(port, ubuf, count, true);
+}
+
+static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
+ size_t count, loff_t *offp)
+{
+ struct port *port;
+
+ port = filp->private_data;
+
+ return send_buf(port, ubuf, count, 0, true);
+}
+
+static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
+{
+ struct port *port;
+ unsigned int ret;
+
+ port = filp->private_data;
+ poll_wait(filp, &port->waitqueue, wait);
+
+ ret = 0;
+ if (!list_empty(&port->readbuf_head))
+ ret |= POLLIN | POLLRDNORM;
+ if (port->host_connected)
+ ret |= POLLOUT;
+ if (!port->host_connected)
+ ret |= POLLHUP;
+
+ return ret;
+}
+
+static int port_fops_release(struct inode *inode, struct file *filp)
+{
+ struct port *port;
+
+ port = filp->private_data;
+
+ /* Notify host of port being closed */
+ send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
+
+ return 0;
+}
+
+static int port_fops_open(struct inode *inode, struct file *filp)
+{
+ struct cdev *cdev = inode->i_cdev;
+ struct port *port;
+
+ port = container_of(cdev, struct port, cdev);
+ filp->private_data = port;
+
+ /*
+ * Don't allow opening of console port devices -- that's done
+ * via /dev/hvc
+ */
+ if (is_console_port(port))
+ return -ENXIO;
+
+ /* Notify host of port being opened */
+ send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
+
+ return 0;
+}
+
+/*
+ * 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
+ * close it. The devices are at
+ * /dev/vport<device number>p<port number>
+ */
+static const struct file_operations port_fops = {
+ .owner = THIS_MODULE,
+ .open = port_fops_open,
+ .read = port_fops_read,
+ .write = port_fops_write,
+ .poll = port_fops_poll,
+ .release = port_fops_release,
+};
+
/*
* The put_chars() callback is pretty straightforward.
*
@@ -618,6 +756,10 @@ static void handle_control_message(struct port *port, struct port_buffer *buf)
port->cons.hvc->irq_requested = 1;
resize_console(port);
break;
+ case VIRTIO_CONSOLE_PORT_OPEN:
+ port->host_connected = cpkt->value;
+ wake_up_interruptible(&port->waitqueue);
+ break;
}
}
@@ -682,10 +824,18 @@ static void rx_work_handler(struct work_struct *work)
kfree(buf);
continue;
}
+ /*
+ * We might have missed a connection notification,
+ * e.g. before the queues were initialised.
+ */
+ port->host_connected = true;
+
spin_lock_irq(&port->readbuf_list_lock);
list_add_tail(&buf->list, &port->readbuf_head);
spin_unlock_irq(&port->readbuf_list_lock);
+ wake_up_interruptible(&port->waitqueue);
+
if (is_console_port(port))
console_activity |= hvc_poll(port->cons.hvc);
}
@@ -751,7 +901,7 @@ static int __devinit add_port(struct ports_device *portdev, u32 id)
port->portdev = portdev;
port->id = id;
- cdev_init(&port->cdev, NULL);
+ cdev_init(&port->cdev, &port_fops);
devt = MKDEV(portdev->chr_major, id);
err = cdev_add(&port->cdev, devt, 1);
@@ -772,6 +922,7 @@ static int __devinit add_port(struct ports_device *portdev, u32 id)
}
spin_lock_init(&port->readbuf_list_lock);
INIT_LIST_HEAD(&port->readbuf_head);
+ init_waitqueue_head(&port->waitqueue);
/*
* If we're not using multiport support, this has to be a console port
diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index ad9557d..14af53d 100644
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -36,6 +36,7 @@ struct virtio_console_control {
#define VIRTIO_CONSOLE_PORT_READY 0
#define VIRTIO_CONSOLE_CONSOLE_PORT 1
#define VIRTIO_CONSOLE_RESIZE 2
+#define VIRTIO_CONSOLE_PORT_OPEN 3
/*
* This struct is put at the start of each buffer that gets passed to
@@ -50,6 +51,8 @@ struct virtio_console_header {
/* Messages between host and guest ('flags' field in the header above) */
#define VIRTIO_CONSOLE_HDR_CONTROL (1 << 0)
+#define VIRTIO_CONSOLE_HDR_START_DATA (1 << 1)
+#define VIRTIO_CONSOLE_HDR_END_DATA (1 << 2)
#ifdef __KERNEL__
int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));
--
1.6.2.5
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