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>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 5e3503a..99d182b 100644 (file)
--- 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;
 

diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index bd0e2a5..1ebf007 100644 (file)
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -40,6 +40,7 @@ struct virtio_console_control {
 #define VIRTIO_CONSOLE_CONSOLE_PORT    1
 #define VIRTIO_CONSOLE_RESIZE          2
 #define VIRTIO_CONSOLE_PORT_OPEN       3
+#define VIRTIO_CONSOLE_PORT_NAME       4
 
 #ifdef __KERNEL__
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));