PCI: Don't allow unbinding host controllers that aren't prepared

Many PCI host controller drivers aren't prepared to have their devices
unbound from them forcefully (e.g., through /sys/.../<driver>/unbind), as
they don't provide any driver .remove callback, where they'd detach the
root bus, release resources, etc. Keeping the driver built in (i.e., not a
loadable module) is not enough; and providing no .remove callback just
means we don't do any teardown.

To rule out the possibility of unbinding a device via sysfs, we need to set
the ".suppress_bind_attrs" field.

I found the suspect drivers via the following search:

  git grep -l platform_driver $(git grep -L -e '\.remove' -e suppress_bind_attrs drivers/pci/)

Then I inspected them to ensure that
(a) they set up a PCI bus in their probe() and
(b) they don't have a remove() callback for undoing the setup

Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/pci/dwc/pci-layerscape.c b/drivers/pci/dwc/pci-layerscape.c
index 8f0ee0d8129c..27d638c4e134 100644
--- a/drivers/pci/dwc/pci-layerscape.c
+++ b/drivers/pci/dwc/pci-layerscape.c
@@ -305,6 +305,7 @@ static struct platform_driver ls_pcie_driver = {
 	.driver = {
 		.name = "layerscape-pcie",
 		.of_match_table = ls_pcie_of_match,
+		.suppress_bind_attrs = true,
 	},
 };
 builtin_platform_driver_probe(ls_pcie_driver, ls_pcie_probe);