linux-kernel - Re: [PATCH 1/1] device core: Add flag to autoremove device link on supplier unbind

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Date:   Wed, 30 May 2018 12:59:43 +0200
From:   "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     gregkh@...uxfoundation.org, lukas@...ner.de,
        dmitry.torokhov@...il.com, aspriel@...il.com, robin.murphy@....com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 1/1] device core: Add flag to autoremove device link on
 supplier unbind

On 5/30/2018 11:57 AM, Vivek Gautam wrote:
> When using the device links without the consumers or
> suppliers maintaining pointers to these links, a flag can
> help in autoremoving the links on supplier driver unbind.
> We remove these links only when the supplier's link to its
> consumers has gone in DL_STATE_SUPPLIER_UNBIND state.
>
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> Suggested-by: Lukas Wunner <lukas@...ner.de>
> ---
>
> Lukas, as suggested in the thread [1] this change adds additional flag
> to autoremove device links on supplier unbind.
> For arm-smmu, we want to _not_ keep references to the device links
> added between arm-smmu, and consumer devices.
> Robin also pointed to [2] the need to autoremove the device link on
> supplier unbind rather than consumer unbind.

Please CC device links patches to linux-pm.

> [1] https://lkml.org/lkml/2018/3/14/390
> [2] https://lkml.org/lkml/2018/5/21/381
>
>   drivers/base/core.c    | 10 ++++++++++
>   include/linux/device.h |  2 ++
>   2 files changed, 12 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index b610816eb887..52c7222bb3c4 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -490,6 +490,16 @@ void device_links_driver_cleanup(struct device *dev)
>   
>   		WARN_ON(link->flags & DL_FLAG_AUTOREMOVE);
>   		WARN_ON(link->status != DL_STATE_SUPPLIER_UNBIND);
> +
> +		/*
> +		 * autoremove the links between this @dev and its consumer
> +		 * devices that are not active, i.e. where the link state
> +		 * has moved to DL_STATE_SUPPLIER_UNBIND.
> +		 */
> +		if (link->status == DL_STATE_SUPPLIER_UNBIND &&
> +		    link->flags & DL_FLAG_AUTOREMOVE_S)
> +			kref_put(&link->kref, __device_link_del);
> +
>   		WRITE_ONCE(link->status, DL_STATE_DORMANT);
>   	}
>   
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 477956990f5e..6033bf58453d 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -779,11 +779,13 @@ enum device_link_state {
>    * AUTOREMOVE: Remove this link automatically on consumer driver unbind.
>    * PM_RUNTIME: If set, the runtime PM framework will use this link.
>    * RPM_ACTIVE: Run pm_runtime_get_sync() on the supplier during link creation.
> + * AUTOREMOVE_S: Remove this link automatically on supplier driver unbind.
>    */
>   #define DL_FLAG_STATELESS	BIT(0)
>   #define DL_FLAG_AUTOREMOVE	BIT(1)
>   #define DL_FLAG_PM_RUNTIME	BIT(2)
>   #define DL_FLAG_RPM_ACTIVE	BIT(3)
> +#define DL_FLAG_AUTOREMOVE_S	BIT(4)

Couldn't you invent a better name for this one?

>   
>   /**
>    * struct device_link - Device link representation.