add cuda_driver_stream variable

Author: sjpb

ansible/roles/cuda/README.md

@@ -2,8 +2,6 @@
 
 Install NVIDIA CUDA. The CUDA binaries are added to the PATH for all users, and the [NVIDIA persistence daemon](https://docs.nvidia.com/deploy/driver-persistence/index.html#persistence-daemon) is enabled.
 
-To avoid unwanted package updates which break functionality, on first use this role enables the dkms-flavour `nvidia-driver` DNF module stream which has the current highest version number. The `latest-dkms` stream is not enabled, and subsequent runs of the role will *not* switch which stream is enabled even if later version streams become available. If an upgrade of the `nvidia-driver` module is required, the currently-enabled stream and all packages should be manually removed.
-
 ## Prerequisites
 
 Requires OFED to be installed to provide required kernel-* packages.
@@ -12,5 +10,6 @@ Requires OFED to be installed to provide required kernel-* packages.
 
 - `cuda_distro`: Optional. Default `rhel8`.
 - `cuda_repo`: Optional. Default `https://developer.download.nvidia.com/compute/cuda/repos/{{ cuda_distro }}/x86_64/cuda-{{ cuda_distro }}.repo`
+- `cuda_driver_stream`: Optional. The default value `default` will, on first use of this role, enable the dkms-flavour `nvidia-driver` DNF module stream with the current highest version number. The `latest-dkms` stream is not enabled, and subsequent runs of the role will *not* change the enabled stream, even if a later version has become available. Changing this value once an `nvidia-driver` stream has been enabled raises an error. If an upgrade of the `nvidia-driver` module is required, the currently-enabled stream and all packages should be manually removed.
 - `cuda_packages`: Optional. Default: `['cuda', 'nvidia-gds']`.
 - `cuda_persistenced_state`: Optional. State of systemd `nvidia-persistenced` service. Values as [ansible.builtin.systemd:state](https://docs.ansible.com/ansible/latest/collections/ansible/builtin/systemd_module.html#parameter-state). Default `started`.

ansible/roles/cuda/defaults/main.yml

@@ -1,5 +1,6 @@
 cuda_distro: rhel8
 cuda_repo: "https://developer.download.nvidia.com/compute/cuda/repos/{{ cuda_distro }}/x86_64/cuda-{{ cuda_distro }}.repo"
+cuda_driver_stream: default
 cuda_packages:
   - cuda
   - nvidia-gds