'simple-mfd' usage implies there might be some kind of resource sharing
between the parent device and its children. By creating a device link
with DL_FLAG_AUTOREMOVE_CONSUMER we make sure that at no point in time
the parent device is unbound while leaving its children unaware that
some of their resources disappeared.
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
Some questions:
- To what extent do we care about cleanly unbinding platform devices at
runtime? My rationale here is: "It's a platform device, for all you
know you might be unbinding someting essential to the system. So if
you're doing it, you better know what you're doing."
- Would this be an abuse of device links?
- If applying this to all simple-mfd devices is a bit too much, would
this be acceptable for a specific device setup. For example RPi4's
firmware interface (simple-mfd user) is passed to consumer drivers
trough a custom API (see rpi_firmware_get()). So, when unbound,
consumers are left with a firmware handle that points to nothing.
drivers/of/platform.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index b557a0fcd4ba..8d5b55b81764 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -390,8 +390,14 @@ static int of_platform_bus_create(struct device_node *bus,
}
dev = of_platform_device_create_pdata(bus, bus_id, platform_data, parent);
- if (!dev || !of_match_node(matches, bus))
- return 0;
+ if (!dev)
+ return 0;
+
+ if (parent && of_device_is_compatible(parent->of_node, "simple-mfd"))
+ device_link_add(&dev->dev, parent, DL_FLAG_AUTOREMOVE_CONSUMER);
+
+ if (!of_match_node(matches, bus))
+ return 0;
for_each_child_of_node(bus, child) {
pr_debug(" create child: %pOF\n", child);
--
2.28.0
