virtio: console: Register with sysfs and create a 'name' attribute for ports

The host can set a name for ports so that they're easily discoverable
instead of going by the /dev/vportNpn naming. This attribute will be
placed in /sys/class/virtio-ports/vportNpn/name. udev scripts can then
create symlinks to the port using the name.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 57 insertions, 0 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 5e3503a31312..99d182b132c4 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -170,6 +170,9 @@ struct port {
         /* A waitqueue for poll() or blocking read operations */
         wait_queue_head_t waitqueue;
 
+        /* The 'name' of the port that we expose via sysfs properties */
+        char *name;
+
         /* The 'id' to identify the port with the Host */
         u32 id;
 
@@ -732,12 +735,36 @@ int init_port_console(struct port *port)
         return 0;
 }
 
+static ssize_t show_port_name(struct device *dev,
+                              struct device_attribute *attr, char *buffer)
+{
+        struct port *port;
+
+        port = dev_get_drvdata(dev);
+
+        return sprintf(buffer, "%s\n", port->name);
+}
+
+static DEVICE_ATTR(name, S_IRUGO, show_port_name, NULL);
+
+static struct attribute *port_sysfs_entries[] = {
+        &dev_attr_name.attr,
+        NULL
+};
+
+static struct attribute_group port_attribute_group = {
+        .name = NULL,           /* put in device directory */
+        .attrs = port_sysfs_entries,
+};
+
 /* Any private messages that the Host and Guest want to share */
 static void handle_control_message(struct ports_device *portdev,
                                    struct port_buffer *buf)
 {
         struct virtio_console_control *cpkt;
         struct port *port;
+        size_t name_size;
+        int err;
 
         cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);
 
@@ -772,6 +799,35 @@ static void handle_control_message(struct ports_device *portdev,
                 port->host_connected = cpkt->value;
                 wake_up_interruptible(&port->waitqueue);
                 break;
+        case VIRTIO_CONSOLE_PORT_NAME:
+                /*
+                 * Skip the size of the header and the cpkt to get the size
+                 * of the name that was sent
+                 */
+                name_size = buf->len - buf->offset - sizeof(*cpkt) + 1;
+
+                port->name = kmalloc(name_size, GFP_KERNEL);
+                if (!port->name) {
+                        dev_err(port->dev,
+                                "Not enough space to store port name\n");
+                        break;
+                }
+                strncpy(port->name, buf->buf + buf->offset + sizeof(*cpkt),
+                        name_size - 1);
+                port->name[name_size - 1] = 0;
+
+                /*
+                 * Since we only have one sysfs attribute, 'name',
+                 * create it only if we have a name for the port.
+                 */
+                err = sysfs_create_group(&port->dev->kobj,
+                                         &port_attribute_group);
+                if (err)
+                        dev_err(port->dev,
+                                "Error %d creating sysfs device attributes\n",
+                                err);
+
+                break;
         }
 }
 
@@ -869,6 +925,7 @@ static int add_port(struct ports_device *portdev, u32 id)
         port->portdev = portdev;
         port->id = id;
 
+        port->name = NULL;
         port->inbuf = NULL;
         port->cons.hvc = NULL;