linux-kernel - Re: [PATCH AUTOSEL 5.6 14/68] driver core: Reevaluate dev->links.need_for

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Date:   Fri, 10 Apr 2020 08:29:31 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Saravana Kannan <saravanak@...gle.com>
Subject: Re: [PATCH AUTOSEL 5.6 14/68] driver core: Reevaluate
 dev->links.need_for_probe as suppliers are added

On Thu, Apr 09, 2020 at 11:45:39PM -0400, Sasha Levin wrote:
> From: Saravana Kannan <saravanak@...gle.com>
> 
> [ Upstream commit 1745d299af5b373abad08fa29bff0d31dc6aff21 ]
> 
> A previous patch 03324507e66c ("driver core: Allow
> fwnode_operations.add_links to differentiate errors") forgot to update
> all call sites to fwnode_operations.add_links. This patch fixes that.
> 
> Legend:
> -> Denotes RHS is an optional/potential supplier for LHS
> => Denotes RHS is a mandatory supplier for LHS
> 
> Example:
> 
> Device A => Device X
> Device A -> Device Y
> 
> Before this patch:
> 1. Device A is added.
> 2. Device A is marked as waiting for mandatory suppliers
> 3. Device X is added
> 4. Device A is left marked as waiting for mandatory suppliers
> 
> Step 4 is wrong since all mandatory suppliers of Device A have been
> added.
> 
> After this patch:
> 1. Device A is added.
> 2. Device A is marked as waiting for mandatory suppliers
> 3. Device X is added
> 4. Device A is no longer considered as waiting for mandatory suppliers
> 
> This is the correct behavior.
> 
> Fixes: 03324507e66c ("driver core: Allow fwnode_operations.add_links to differentiate errors")
> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> Link: https://lore.kernel.org/r/20200222014038.180923-2-saravanak@google.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/base/core.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index dbb0f9130f42d..d32a3aefff32f 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -523,9 +523,13 @@ static void device_link_add_missing_supplier_links(void)
>  
>  	mutex_lock(&wfs_lock);
>  	list_for_each_entry_safe(dev, tmp, &wait_for_suppliers,
> -				 links.needs_suppliers)
> -		if (!fwnode_call_int_op(dev->fwnode, add_links, dev))
> +				 links.needs_suppliers) {
> +		int ret = fwnode_call_int_op(dev->fwnode, add_links, dev);
> +		if (!ret)
>  			list_del_init(&dev->links.needs_suppliers);
> +		else if (ret != -ENODEV)
> +			dev->links.need_for_probe = false;
> +	}
>  	mutex_unlock(&wfs_lock);
>  }

For some reason this wasn't for stable kernels, but I can't remember.

Saravana, any thoughts?

greg k-h