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SubjectRe: [PATCH v1 08/12] usb: roles: Add usb role switch notifier.
On Mon, Dec 03, 2018 at 11:45:11AM +0800, Yu Chen wrote:
> This patch adds notifier for drivers want to be informed of the usb role switch.

I think in this case it would be good to explain a little for what we
need the notifier for.

> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
> Cc: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Signed-off-by: Yu Chen <chenyu56@huawei.com>
>
> --
> v0:
> The patch is provided by Heikki Krogerus. I modified and test it
> on Hikey960 platform.

I don't think I actually made a "patch" for this. The "diff" I made
showing the idea does not count, so you should not sign off the patch
with my address.

In this case I believe something like "Suggested-by" should be used
instead of SoB tag:

Suggested-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

Side note: If this was from me, then there should be "from" line with
my address as well.

> --
> ---
> drivers/usb/common/roles.c | 20 +++++++++++++++++++-
> include/linux/usb/role.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 65 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/common/roles.c b/drivers/usb/common/roles.c
> index 0f48090c5c30..bfd7a988b64c 100644
> --- a/drivers/usb/common/roles.c
> +++ b/drivers/usb/common/roles.c
> @@ -21,6 +21,7 @@ struct usb_role_switch {
> struct device dev;
> struct mutex lock; /* device lock*/
> enum usb_role role;
> + struct blocking_notifier_head nh;
>
> /* From descriptor */
> struct device *usb2_port;
> @@ -50,8 +51,10 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role)
> mutex_lock(&sw->lock);
>
> ret = sw->set(sw->dev.parent, role);
> - if (!ret)
> + if (!ret) {
> sw->role = role;
> + blocking_notifier_call_chain(&sw->nh, role, NULL);
> + }
>
> mutex_unlock(&sw->lock);
>
> @@ -59,6 +62,20 @@ int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role)
> }
> EXPORT_SYMBOL_GPL(usb_role_switch_set_role);
>
> +int usb_role_switch_register_notifier(struct usb_role_switch *sw,
> + struct notifier_block *nb)
> +{
> + return blocking_notifier_chain_register(&sw->nh, nb);
> +}
> +EXPORT_SYMBOL_GPL(usb_role_switch_register_notifier);
> +
> +int usb_role_switch_unregister_notifier(struct usb_role_switch *sw,
> + struct notifier_block *nb)
> +{
> + return blocking_notifier_chain_unregister(&sw->nh, nb);
> +}
> +EXPORT_SYMBOL_GPL(usb_role_switch_unregister_notifier);
> +
> /**
> * usb_role_switch_get_role - Get the USB role for a switch
> * @sw: USB role switch
> @@ -297,6 +314,7 @@ usb_role_switch_register(struct device *parent,
> return ERR_PTR(-ENOMEM);
>
> mutex_init(&sw->lock);
> + BLOCKING_INIT_NOTIFIER_HEAD(&sw->nh);
>
> sw->allow_userspace_control = desc->allow_userspace_control;
> sw->usb2_port = desc->usb2_port;
> diff --git a/include/linux/usb/role.h b/include/linux/usb/role.h
> index edc51be4a77c..c97d4be91ada 100644
> --- a/include/linux/usb/role.h
> +++ b/include/linux/usb/role.h
> @@ -40,6 +40,8 @@ struct usb_role_switch_desc {
> bool allow_userspace_control;
> };
>
> +
> +#if IS_ENABLED(CONFIG_USB_ROLE_SWITCH)
> int usb_role_switch_set_role(struct usb_role_switch *sw, enum usb_role role);
> enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw);
> struct usb_role_switch *usb_role_switch_get(struct device *dev);
> @@ -49,5 +51,49 @@ struct usb_role_switch *
> usb_role_switch_register(struct device *parent,
> const struct usb_role_switch_desc *desc);
> void usb_role_switch_unregister(struct usb_role_switch *sw);
> +int usb_role_switch_register_notifier(struct usb_role_switch *sw,
> + struct notifier_block *nb);
> +int usb_role_switch_unregister_notifier(struct usb_role_switch *sw,
> + struct notifier_block *nb);
> +#else
> +static inline int usb_role_switch_set_role(struct usb_role_switch *sw,
> + enum usb_role role)
> +{
> + return 0;
> +}
> +
> +static inline enum usb_role usb_role_switch_get_role(struct usb_role_switch *sw)
> +{
> + return USB_ROLE_NONE;
> +}
> +
> +static inline struct usb_role_switch *usb_role_switch_get(struct device *dev)
> +{
> + return ERR_PTR(-ENODEV);
> +}
> +
> +static inline void usb_role_switch_put(struct usb_role_switch *sw) { }
> +
> +static inline struct usb_role_switch *
> +usb_role_switch_register(struct device *parent,
> + const struct usb_role_switch_desc *desc)
> +{
> + return ERR_PTR(-ENODEV);
> +}
> +
> +static inline void usb_role_switch_unregister(struct usb_role_switch *sw) { }
> +
> +static int usb_role_switch_register_notifier(struct usb_role_switch *sw,
> + struct notifier_block *nb)
> +{
> + return -ENODEV;
> +}
> +
> +static int usb_role_switch_unregister_notifier(struct usb_role_switch *sw,
> + struct notifier_block *nb)
> +{
> + return -ENODEV;
> +}
> +#endif
>
> #endif /* __LINUX_USB_ROLE_H */
> --
> 2.15.0-rc2

thanks,

--
heikki

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