[PATCH v3 5/5] mtty: Optionally support mtty alias

[Parav Pandit]

Provide a module parameter to set alias length to optionally generate
mdev alias.

Example to request mdev alias.
$ modprobe mtty alias_length=12

Make use of mtty_alias() API when alias_length module parameter is set.

Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx>
---
Changelog:
v1->v2:
 - Added mdev_alias() usage sample
---
 samples/vfio-mdev/mtty.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 92e770a06ea2..075d65440bc0 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -150,6 +150,10 @@ static const struct file_operations vd_fops = {
 	.owner          = THIS_MODULE,
 };
 
+static unsigned int mtty_alias_length;
+module_param_named(alias_length, mtty_alias_length, uint, 0444);
+MODULE_PARM_DESC(alias_length, "mdev alias length; default=0");
+
 /* function prototypes */
 
 static int mtty_trigger_interrupt(const guid_t *uuid);
@@ -770,6 +774,9 @@ static int mtty_create(struct kobject *kobj, struct mdev_device *mdev)
 	list_add(&mdev_state->next, &mdev_devices_list);
 	mutex_unlock(&mdev_list_lock);
 
+	if (mtty_alias_length)
+		dev_dbg(mdev_dev(mdev), "alias is %s\n", mdev_alias(mdev));
+
 	return 0;
 }
 
@@ -1410,6 +1417,11 @@ static struct attribute_group *mdev_type_groups[] = {
 	NULL,
 };
 
+static unsigned int mtty_get_alias_length(void)
+{
+	return mtty_alias_length;
+}
+
 static const struct mdev_parent_ops mdev_fops = {
 	.owner                  = THIS_MODULE,
 	.dev_attr_groups        = mtty_dev_groups,
@@ -1422,6 +1434,7 @@ static const struct mdev_parent_ops mdev_fops = {
 	.read                   = mtty_read,
 	.write                  = mtty_write,
 	.ioctl		        = mtty_ioctl,
+	.get_alias_length	= mtty_get_alias_length
 };
 
 static void mtty_device_release(struct device *dev)
-- 
2.19.2