dmaengine: idxd: create user driver for wq 'device'

The original architecture of /sys/bus/dsa invented a scheme whereby a
single entry in the list of bus drivers, /sys/bus/drivers/dsa, handled
all device types and internally routed them to different drivers.
Those internal drivers were invisible to userspace. Now, as
/sys/bus/dsa wants to grow support for alternate drivers for a given
device, for example vfio-mdev instead of kernel-internal-dmaengine, a
proper bus device-driver model is needed. The first step in that process
is separating the existing omnibus/implicit "dsa" driver into proper
individual drivers registered on /sys/bus/dsa. Establish the
idxd_user_drv driver that controls the enabling and disabling of the
wq and also register and unregister a char device to allow user space
to mmap the descriptor submission portal.

The cdev related bits are moved to the cdev driver probe/remove and out of
the drv_enabe/disable_wq() calls. These bits are exclusive to the cdev
operation and not part of the generic enable/disable of the wq device.

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/162637467578.744545.10203997610072341376.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/cdev.c

@@ -304,6 +304,59 @@ void idxd_wq_del_cdev(struct idxd_wq *wq)
 	put_device(cdev_dev(idxd_cdev));
 }
 
+static int idxd_user_drv_probe(struct idxd_dev *idxd_dev)
+{
+	struct idxd_wq *wq = idxd_dev_to_wq(idxd_dev);
+	struct idxd_device *idxd = wq->idxd;
+	int rc;
+
+	if (idxd->state != IDXD_DEV_ENABLED)
+		return -ENXIO;
+
+	mutex_lock(&wq->wq_lock);
+	wq->type = IDXD_WQT_USER;
+	rc = __drv_enable_wq(wq);
+	if (rc < 0)
+		goto err;
+
+	rc = idxd_wq_add_cdev(wq);
+	if (rc < 0)
+		goto err_cdev;
+
+	mutex_unlock(&wq->wq_lock);
+	return 0;
+
+err_cdev:
+	__drv_disable_wq(wq);
+err:
+	wq->type = IDXD_WQT_NONE;
+	mutex_unlock(&wq->wq_lock);
+	return rc;
+}
+
+static void idxd_user_drv_remove(struct idxd_dev *idxd_dev)
+{
+	struct idxd_wq *wq = idxd_dev_to_wq(idxd_dev);
+
+	mutex_lock(&wq->wq_lock);
+	idxd_wq_del_cdev(wq);
+	__drv_disable_wq(wq);
+	wq->type = IDXD_WQT_NONE;
+	mutex_unlock(&wq->wq_lock);
+}
+
+static enum idxd_dev_type dev_types[] = {
+	IDXD_DEV_WQ,
+	IDXD_DEV_NONE,
+};
+
+struct idxd_device_driver idxd_user_drv = {
+	.probe = idxd_user_drv_probe,
+	.remove = idxd_user_drv_remove,
+	.name = "user",
+	.type = dev_types,
+};
+
 int idxd_cdev_register(void)
 {
 	int rc, i;

drivers/dma/idxd/device.c

@@ -1201,19 +1201,8 @@ int __drv_enable_wq(struct idxd_wq *wq)
 	}
 
 	wq->client_count = 0;
-
-	if (is_idxd_wq_cdev(wq)) {
-		rc = idxd_wq_add_cdev(wq);
-		if (rc < 0) {
-			dev_dbg(dev, "wq %d cdev creation failed\n", wq->id);
-			goto err_client;
-		}
-	}
-
 	return 0;
 
-err_client:
-	idxd_wq_unmap_portal(wq);
 err_map_portal:
 	rc = idxd_wq_disable(wq, false);
 	if (rc < 0)
@@ -1239,9 +1228,6 @@ void __drv_disable_wq(struct idxd_wq *wq)
 
 	lockdep_assert_held(&wq->wq_lock);
 
-	if (is_idxd_wq_cdev(wq))
-		idxd_wq_del_cdev(wq);
-
 	if (idxd_wq_refcount(wq))
 		dev_warn(dev, "Clients has claim on wq %d: %d\n",
 			 wq->id, idxd_wq_refcount(wq));

drivers/dma/idxd/idxd.h

@@ -60,6 +60,7 @@ struct idxd_device_driver {
 extern struct idxd_device_driver dsa_drv;
 extern struct idxd_device_driver idxd_drv;
 extern struct idxd_device_driver idxd_dmaengine_drv;
+extern struct idxd_device_driver idxd_user_drv;
 
 struct idxd_irq_entry {
 	struct idxd_device *idxd;

drivers/dma/idxd/init.c

@@ -848,6 +848,10 @@ static int __init idxd_init_module(void)
 	if (err < 0)
 		goto err_idxd_dmaengine_driver_register;
 
+	err = idxd_driver_register(&idxd_user_drv);
+	if (err < 0)
+		goto err_idxd_user_driver_register;
+
 	err = idxd_driver_register(&dsa_drv);
 	if (err < 0)
 		goto err_dsa_driver_register;
@@ -867,6 +871,8 @@ static int __init idxd_init_module(void)
 err_cdev_register:
 	idxd_driver_unregister(&dsa_drv);
 err_dsa_driver_register:
+	idxd_driver_unregister(&idxd_user_drv);
+err_idxd_user_driver_register:
 	idxd_driver_unregister(&idxd_dmaengine_drv);
 err_idxd_dmaengine_driver_register:
 	idxd_driver_unregister(&idxd_drv);
@@ -878,6 +884,7 @@ module_init(idxd_init_module);
 
 static void __exit idxd_exit_module(void)
 {
+	idxd_driver_unregister(&idxd_user_drv);
 	idxd_driver_unregister(&idxd_dmaengine_drv);
 	idxd_driver_unregister(&idxd_drv);
 	idxd_driver_unregister(&dsa_drv);