Re: [[PATCH repost v21] 01/11] of/overlay: add of overlay notifications

[Moritz Fischer]

On Tue, Nov 1, 2016 at 1:14 PM, Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx> 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 of_mutex is held during these notifications. 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>
> Acked-by: Rob Herring <robh@xxxxxxxxxx>
Acked-by: Moritz Fischer <moritz.fischer@xxxxxxxxx>
> ---
>  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 318dbb5..0d4cda7 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -58,6 +58,41 @@ 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)
>  {
> @@ -368,6 +403,13 @@ 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)
> @@ -382,6 +424,8 @@ 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;
> @@ -498,9 +542,10 @@ 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 299aeb1..d72f010 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -1266,6 +1266,18 @@ static inline bool of_device_is_system_power_controller(const struct device_node
>   * Overlay support
>   */
>
> +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;
> +};
> +
>  #ifdef CONFIG_OF_OVERLAY
>
>  /* ID based overlays; the API for external users */
> @@ -1273,6 +1285,9 @@ static inline bool of_device_is_system_power_controller(const struct device_node
>  int of_overlay_destroy(int id);
>  int of_overlay_destroy_all(void);
>
> +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)
> @@ -1290,6 +1305,16 @@ static inline int of_overlay_destroy_all(void)
>         return -ENOTSUPP;
>  }
>
> +static inline int of_overlay_notifier_register(struct notifier_block *nb)
> +{
> +       return 0;
> +}
> +
> +static inline int of_overlay_notifier_unregister(struct notifier_block *nb)
> +{
> +       return 0;
> +}
> +
>  #endif
>
>  #endif /* _LINUX_OF_H */
> --
> 1.9.1
>