linux-kernel - Re: [PATCH 1/4] usb: typec: Add port registration notifier

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Date:   Wed, 24 Nov 2021 19:20:42 -0800
From:   Prashant Malani <pmalani@...omium.org>
To:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Cc:     wonchung@...gle.com, bleung@...omium.org,
        heikki.krogerus@...ux.intel.com,
        Alan Stern <stern@...land.harvard.edu>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christian König <christian.koenig@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Rajat Jain <rajatja@...gle.com>,
        Rikard Falkeborn <rikard.falkeborn@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH 1/4] usb: typec: Add port registration notifier

On Wed, Nov 24, 2021 at 3:11 PM Prashant Malani <pmalani@...omium.org> wrote:
>
> Introduce a blocking notifier to be called when a new Type C port gets
> registered with the connector class framework.
>
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
> NOTE: typec_port_registration_register_notify() is a bit long,
> so please let me know if you have any shorter suggestions for naming
> this function.
>
>  drivers/usb/typec/class.c | 30 ++++++++++++++++++++++++++++++
>  include/linux/usb/typec.h | 13 +++++++++++++
>  2 files changed, 43 insertions(+)
>
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index aeef453aa658..14b82109b0f5 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -16,6 +16,8 @@
>  #include "bus.h"
>  #include "class.h"
>
> +static BLOCKING_NOTIFIER_HEAD(typec_port_registration_notifier);
> +
>  static DEFINE_IDA(typec_index_ida);
>
>  struct class typec_class = {
> @@ -1979,6 +1981,32 @@ void typec_port_register_altmodes(struct typec_port *port,
>  }
>  EXPORT_SYMBOL_GPL(typec_port_register_altmodes);
>
> +/**
> + *  typec_port_registration_register_notify - Register a notifier for Type C port registration.
> + *  @nb: notifier block to signal
> + *
> + *  This function allows callers to get a notification when a Type C port is registered with
> + *  the connector class.
> + */
> +int typec_port_registration_register_notify(struct notifier_block *nb)
> +{
> +       return blocking_notifier_chain_register(&typec_port_registration_notifier, nb);
> +}
> +EXPORT_SYMBOL_GPL(typec_port_registration_register_notify);
> +
> +/**
> + *  typec_port_registration_unregister_notify - Unregister a notifier for Type C port registration.
> + *  @nb: notifier block to unregister
> + *
> + *  This function allows callers to unregister notifiers which were previously registered using
> + *  typec_port_registration_register_notify().
> + */
> +int typec_port_registration_unregister_notify(struct notifier_block *nb)
> +{
> +       return blocking_notifier_chain_unregister(&typec_port_registration_notifier, nb);
> +}
> +EXPORT_SYMBOL_GPL(typec_port_registration_unregister_notify);
> +
>  /**
>   * typec_register_port - Register a USB Type-C Port
>   * @parent: Parent device
> @@ -2086,6 +2114,8 @@ struct typec_port *typec_register_port(struct device *parent,
>         if (ret)
>                 dev_warn(&port->dev, "failed to create symlinks (%d)\n", ret);
>
> +       blocking_notifier_call_chain(&typec_port_registration_notifier, 0, port);
> +
>         return port;
>  }
>  EXPORT_SYMBOL_GPL(typec_register_port);
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index e2e44bb1dad8..398317835f24 100644
> --- a/include/linux/usb/typec.h
> +++ b/include/linux/usb/typec.h
> @@ -3,6 +3,7 @@
>  #ifndef __LINUX_USB_TYPEC_H
>  #define __LINUX_USB_TYPEC_H
>
> +#include <linux/notifier.h>
>  #include <linux/types.h>
>
>  /* USB Type-C Specification releases */
> @@ -308,6 +309,8 @@ int typec_get_negotiated_svdm_version(struct typec_port *port);
>  #if IS_REACHABLE(CONFIG_TYPEC)
>  int typec_link_port(struct device *port);
>  void typec_unlink_port(struct device *port);
> +int typec_port_registration_register_notify(struct notifier_block *nb);
> +int typec_port_registration_unregister_notify(struct notifier_block *nb);
>  #else
>  static inline int typec_link_port(struct device *port)
>  {
> @@ -315,6 +318,16 @@ static inline int typec_link_port(struct device *port)
>  }
>
>  static inline void typec_unlink_port(struct device *port) { }
> +
> +int typec_port_registration_register_notify(struct notifier_block *nb)
> +{
> +       return 0;
> +}
> +
> +int typec_port_registration_unregister_notify(struct notifier_block *nb)
> +{
> +       return 0;
> +}
>  #endif

Oops, looks like I forgot to static inline these....

Also, probably better to return -ENODEV for these calls?

Sorry about that; I'll fix it up and send another version.

Thanks,