linux-kernel - Re: [PATCH] platform: release resource itself instead of resource tree

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Date:   Thu, 25 Jul 2019 15:38:50 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     junxiao.chang@...el.com
Cc:     linux-kernel@...r.kernel.org, rafael@...nel.org, lili.li@...el.com
Subject: Re: [PATCH] platform: release resource itself instead of resource
 tree

On Thu, Apr 25, 2019 at 02:24:18PM +0800, junxiao.chang@...el.com wrote:
> From: Junxiao Chang <junxiao.chang@...el.com>
> 
> When platform device is deleted or there is error in adding
> device, platform device resources should be released. Currently
> API release_resource is used to release platform device resources.
> However, this API releases not only platform resource itself but
> also its child resources. It might release resources which are
> still in use. Calling remove_resource only releases current
> resource itself, not resource tree, it moves its child resources
> to up level.

But shouldn't the parent device not get removed until all of the
children are removed?  What is causing this "inversion" to happen?

> 
> For example, platform device 1 and device 2 are registered, then only
> device 1 is unregistered in below code:
> 
>   ...
>   // Register platform test device 1, resource 0xfed1a000 ~ 0xfed1afff
>   pdev1 = platform_device_register_full(&pdevinfo1);
> 
>   // Register platform test device 2, resource 0xfed1a200 ~ 0xfed1a2ff
>   pdev2 = platform_device_register_full(&pdevinfo2);
> 
>   // Now platform device 2 resource should be device 1 resource's child
> 
>   // Unregister device 1 only
>   platform_device_unregister(pdev1);
>   ...

Don't do that.  :)

You created this mess of platform devices, so you need to keep track of
them.


> Platform device 2 resource will be released as well because its
> parent resource(device 1's resource) is released, this is not expected.
> If using API remove_resource, device 2 resource will not be released.
> 
> This change fixed an intel pmc platform device resource issue when
> intel pmc ipc kernel module is inserted/removed for twice.

Why not fix that kernel module instead?  It seems like that is the real
problem here, not a driver core issue.

thanks,

greg k-h