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>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 6f38128ce400..33a80f700ff8 100644
--- a/drivers/dma/idxd/init.c
+++ b/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 @@ err_pci_register:
 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);