Re: [PATCH] of/overlay: add of overlay notifications

[atull]

On Thu, 25 Feb 2016, Alan Tull wrote:

> This patch add of overlay notifications.
> 
> When DT overlays are being added, some drivers/subsystems
> need to see device tree overlays before the changes go into
> the live tree.
> 
> This is distinct from reconfig notifiers that are
> post-apply or post-remove and which issue very granular
> notifications without providing access to the context
> of a whole overlay.
> 
> The following 4 notificatons are issued:
>   OF_OVERLAY_PRE_APPLY
>   OF_OVERLAY_POST_APPLY
>   OF_OVERLAY_PRE_REMOVE
>   OF_OVERLAY_POST_REMOVE
> 
> In the case of pre-apply notification, if the notifier
> returns error, the overlay will be rejected.
> 
> This patch exports two functions for registering/unregistering
> notifications:
>   of_overlay_notifier_register(struct notifier_block *nb)
>   of_overlay_notifier_unregister(struct notifier_block *nb)
> 
> The notification data includes pointers to the overlay
> target and the overlay:
> 
> struct of_overlay_notify_data {
>        struct device_node *overlay;
>        struct device_node *target;
> };
> 
> Signed-off-by: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/of/overlay.c |   47 ++++++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/of.h   |   25 +++++++++++++++++++++++++
>  2 files changed, 71 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index 8225081..a26f0ed 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -56,6 +56,41 @@ struct of_overlay {
>  static int of_overlay_apply_one(struct of_overlay *ov,
>  		struct device_node *target, const struct device_node *overlay);
>  
> +static BLOCKING_NOTIFIER_HEAD(of_overlay_chain);
> +
> +int of_overlay_notifier_register(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&of_overlay_chain, nb);
> +}
> +EXPORT_SYMBOL_GPL(of_overlay_notifier_register);
> +
> +int of_overlay_notifier_unregister(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_unregister(&of_overlay_chain, nb);
> +}
> +EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);
> +
> +static int of_overlay_notify(struct of_overlay *ov,
> +			     enum of_overlay_notify_action action)
> +{
> +	struct of_overlay_notify_data nd;
> +	int i, ret;
> +
> +	for (i = 0; i < ov->count; i++) {
> +		struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i];
> +
> +		nd.target = ovinfo->target;
> +		nd.overlay = ovinfo->overlay;
> +
> +		ret = blocking_notifier_call_chain(&of_overlay_chain,
> +						   action, &nd);
> +		if (ret)
> +			return notifier_to_errno(ret);
> +	}
> +
> +	return 0;
> +}
> +
>  static int of_overlay_apply_single_property(struct of_overlay *ov,
>  		struct device_node *target, struct property *prop)
>  {
> @@ -370,6 +405,13 @@ int of_overlay_create(struct device_node *tree)
>  		goto err_free_idr;
>  	}
>  
> +	err = of_overlay_notify(ov, OF_OVERLAY_PRE_APPLY);
> +	if (err < 0) {
> +		pr_err("%s: Pre-apply notifier failed (err=%d)\n",
> +		       __func__, err);
> +		goto err_free_idr;
> +	}
> +
>  	/* apply the overlay */
>  	err = of_overlay_apply(ov);
>  	if (err) {
> @@ -389,6 +431,8 @@ int of_overlay_create(struct device_node *tree)
>  	/* add to the tail of the overlay list */
>  	list_add_tail(&ov->node, &ov_list);
>  
> +	of_overlay_notify(ov, OF_OVERLAY_POST_APPLY);
> +
>  	mutex_unlock(&of_mutex);
>  
>  	return id;
> @@ -509,9 +553,10 @@ int of_overlay_destroy(int id)
>  		goto out;
>  	}
>  
> -
> +	of_overlay_notify(ov, OF_OVERLAY_PRE_REMOVE);
>  	list_del(&ov->node);
>  	__of_changeset_revert(&ov->cset);
> +	of_overlay_notify(ov, OF_OVERLAY_POST_REMOVE);
>  	of_free_overlay_info(ov);
>  	idr_remove(&ov_idr, id);
>  	of_changeset_destroy(&ov->cset);
> diff --git a/include/linux/of.h b/include/linux/of.h
> index dc6e396..e70a686 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -1083,6 +1083,21 @@ int of_overlay_create(struct device_node *tree);
>  int of_overlay_destroy(int id);
>  int of_overlay_destroy_all(void);
>  
> +enum of_overlay_notify_action {
> +	OF_OVERLAY_PRE_APPLY,
> +	OF_OVERLAY_POST_APPLY,
> +	OF_OVERLAY_PRE_REMOVE,
> +	OF_OVERLAY_POST_REMOVE,
> +};
> +
> +struct of_overlay_notify_data {
> +	struct device_node *overlay;
> +	struct device_node *target;
> +};
> +
> +int of_overlay_notifier_register(struct notifier_block *nb);
> +int of_overlay_notifier_unregister(struct notifier_block *nb);
> +
>  #else
>  
>  static inline int of_overlay_create(struct device_node *tree)
> @@ -1100,6 +1115,16 @@ static inline int of_overlay_destroy_all(void)
>  	return -ENOTSUPP;
>  }
>  
> +int of_overlay_notifier_register(struct notifier_block *nb)

Needs 'static inline'

> +{
> +	return 0;
> +}
> +
> +int of_overlay_notifier_unregister(struct notifier_block *nb)

Needs 'static inline'

Alan

> +{
> +	return 0;
> +}
> +
>  #endif
>  
>  #endif /* _LINUX_OF_H */
> -- 
> 1.7.9.5
> 
>