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Consider this example where -> means LHS device is a consumer of RHS
device and indentation represents "child of" of the previous device.
Device A -> Device C
Device B -> Device A
Device C
Without this commit:
1. Device A is added.
2. Device A is added to waiting for supplier list (Device C)
3. Device B is added
4. Device B is linked as a consumer to Device A
5. Device A doesn't probe because it's waiting for Device C to be added.
6. Device B doesn't probe because Device A hasn't probed.
7. Device C will never be added because it's parent hasn't probed.
So, Device A, B and C will be in a probe/add deadlock.
This commit detects this scenario and stops trying to create a device
link between Device A and Device C since doing so would create the
following cycle:
Device A -> Devic C -(parent)-> Device B -> Device A.
With this commit:
1. Device A is added.
3. Device B is added
4. Device B is linked as a consumer to Device A
5. Device A probes.
6. Device B probes because Device A has probed.
7. Device C is added and probed.
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200610011934.49795-3-saravanak@google.com
Signed-off-by: Rob Herring <robh@kernel.org>
(cherry picked from commit
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|---|---|---|
| .. | ||
| unittest-data | ||
| address.c | ||
| base.c | ||
| device.c | ||
| dynamic.c | ||
| fdt_address.c | ||
| fdt.c | ||
| irq.c | ||
| Kconfig | ||
| kobj.c | ||
| Makefile | ||
| of_mdio.c | ||
| of_net.c | ||
| of_numa.c | ||
| of_private.h | ||
| of_reserved_mem.c | ||
| overlay.c | ||
| pdt.c | ||
| platform.c | ||
| property.c | ||
| resolver.c | ||
| unittest.c | ||