virtio_console: support console resizing

this patch uses the new hvc callback hvc_resize to set the window size
which allows to change the tty size of hvc_console via a hvc_resize
function.

I have added a new feature bit VIRTIO_CONSOLE_F_SIZE. The driver will
change the window size on tty open and via the config_changed callback
of the transport. Currently lguest and kvm_s390 have not implemented this
callback, but the callback can be implemented at a later point in time.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 30 insertions, 1 deletions

diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index fb57f67bb427..0587b66d6fc7 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -695,6 +695,7 @@ void hvc_resize(struct hvc_struct *hp, struct winsize ws)
         hp->ws = ws;
         schedule_work(&hp->tty_resize);
 }
+EXPORT_SYMBOL_GPL(hvc_resize);
 
 /*
  * This kthread is either polling or interrupt driven.  This is determined by
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 3fb0d2c88ba5..ff6f5a4b58fb 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -138,12 +138,33 @@ int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int))
 }
 
 /*
+ * virtio console configuration. This supports:
+ * - console resize
+ */
+static void virtcons_apply_config(struct virtio_device *dev)
+{
+        struct winsize ws;
+
+        if (virtio_has_feature(dev, VIRTIO_CONSOLE_F_SIZE)) {
+                dev->config->get(dev,
+                                 offsetof(struct virtio_console_config, cols),
+                                 &ws.ws_col, sizeof(u16));
+                dev->config->get(dev,
+                                 offsetof(struct virtio_console_config, rows),
+                                 &ws.ws_row, sizeof(u16));
+                hvc_resize(hvc, ws);
+        }
+}
+
+/*
  * we support only one console, the hvc struct is a global var
- * There is no need to do anything
+ * We set the configuration at this point, since we now have a tty
  */
 static int notifier_add_vio(struct hvc_struct *hp, int data)
 {
         hp->irq_requested = 1;
+        virtcons_apply_config(vdev);
+
         return 0;
 }
 
@@ -234,11 +255,18 @@ static struct virtio_device_id id_table[] = {
         { 0 },
 };
 
+static unsigned int features[] = {
+        VIRTIO_CONSOLE_F_SIZE,
+};
+
 static struct virtio_driver virtio_console = {
+        .feature_table = features,
+        .feature_table_size = ARRAY_SIZE(features),
         .driver.name =  KBUILD_MODNAME,
         .driver.owner = THIS_MODULE,
         .id_table =     id_table,
         .probe =        virtcons_probe,
+        .config_changed = virtcons_apply_config,
 };
 
 static int __init init(void)