[PATCH 2/2] host/rootfs: /etc/mdev/net/add: make idempotent

[Alyssa Ross <hi@alyssa.is>]

udev actions needs to be idempotent, so when we switch to udev, we
have the choice of making this script idempotent, or doing goto hacks
to stop udev running it more than once.  I like this better.

assign-devices is already idempotent, so all we need to do to achieve
idempotency is avoid unbinding and rebinding the driver if it's
already the right one.

Link: https://spectrum-os.org/lists/archives/spectrum-devel/87ikgxwq0v.fsf@alyssa.is
Signed-off-by: Alyssa Ross <hi@alyssa.is>
---
 host/rootfs/image/etc/mdev/net/add | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/host/rootfs/image/etc/mdev/net/add b/host/rootfs/image/etc/mdev/net/add
index f343779..62c152e 100755
--- a/host/rootfs/image/etc/mdev/net/add
+++ b/host/rootfs/image/etc/mdev/net/add
@@ -1,6 +1,6 @@
 #!/bin/execlineb -P
 # SPDX-License-Identifier: EUPL-1.2+
-# SPDX-FileCopyrightText: 2021 Alyssa Ross <hi@alyssa.is>
+# SPDX-FileCopyrightText: 2021, 2025 Alyssa Ross <hi@alyssa.is>
 
 # Assign the whole IOMMU group containing this device to the network
 # VM.
@@ -12,6 +12,13 @@ importas -i devpath DEVPATH
 foreground {
   pipeline { ls -1 /sys${devpath}/iommu_group/devices }
   forstdin -pE device
+  if -t {
+    backtick -E driver_name {
+      backtick -E driver_path { readlink /sys/bus/pci/devices/${device}/driver }
+      basename -- $driver_path
+    }
+    test $driver_name != vfio-pci
+  }
   foreground {
     redirfd -w 2 /dev/null
     redirfd -w 1 /sys/bus/pci/devices/${device}/driver/unbind
-- 
2.51.0