On Thu, 16 Dec 2010, Pavankumar Kondeti wrote:
> OTG supplement revision 2.0 spec introduces Attach Detection Protocol
> (ADP) for detecting peripheral connection without applying power on
> VBUS. ADP is optional and is included in the OTG descriptor along with
> SRP and HNP.
>
> HNP polling is introduced for peripheral to notify its wish to become
> host. Host polls (GET_STATUS on DEVICE) peripheral for host_request
> and suspend the bus when peripheral returns host_request TRUE. The spec
> insists the polling frequency to be in 1-2 sec range and bus should be
> suspended within 2 sec from host_request is set.
>
> a_alt_hnp_support feature is obsolete and a_hnp_support feature is limited
> to only legacy OTG B-device. The newly introduced bcdOTG field in the OTG
> descriptor is used for identifying the 2.0 compliant B-device.
This combination of things doesn't make sense:
> index b9278a1..baada06 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -1270,6 +1282,47 @@ static int usb_resume_both(struct usb_device *udev, pm_message_t msg)
> return status;
> }
>
> +#ifdef CONFIG_USB_OTG
> +void usb_hnp_polling_work(struct work_struct *work)
> +{
...
> +}
> +#endif
usb_hnp_polling_work() is defined only when CONFIG_USB_OTG is set.
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index e70aeaf..5dd59e9 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -869,6 +869,7 @@ static void usb_bus_init (struct usb_bus *bus)
> bus->bandwidth_isoc_reqs = 0;
>
> INIT_LIST_HEAD (&bus->bus_list);
> + INIT_DELAYED_WORK(&bus->hnp_polling, usb_hnp_polling_work);
> }
But its address is taken regardless of CONFIG_USB_OTG.
> diff --git a/drivers/usb/core/usb.h b/drivers/usb/core/usb.h
> index b975450..ffa16e1 100644
> --- a/drivers/usb/core/usb.h
> +++ b/drivers/usb/core/usb.h
> @@ -72,6 +72,14 @@ static inline int usb_port_resume(struct usb_device *udev, pm_message_t msg)
>
> #endif
>
> +#ifdef CONFIG_USB_OTG
> +extern void usb_hnp_polling_work(struct work_struct *work);
> +#else
> +static inline void usb_hnp_polling_work(struct work_struct *work)
> +{
> +}
> +#endif
Otherwise it is an empty inline routine.
But taking the address of an inline routine forces the compiler to
produce an out-of-line version. Therefore you might as well explicitly
define usb_hnp_polling_work() as an empty function when CONFIG_USB_OTG
isn't set.
Alan Stern
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