Re: [PATCH v2 2/2] of: property: Improve cycle detection when one of the devices is never added

[Rob Herring]

On Tue, 09 Jun 2020 18:19:34 -0700, Saravana Kannan wrote:
> 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@xxxxxxxxxx>
> ---
>  drivers/of/property.c | 62 ++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 56 insertions(+), 6 deletions(-)
> 

Both patches applied.

Rob