Peter Chen <peter.chen@xxxxxxxxxxxxx> writes:
> Currently, connect gadget is unconditional after binding,
> but some function drivers may want to connect gadget on the fly.
> With this API, the function driver can disconnect gadget during
> the initialization, and connect gadget when it wants.
>
> During this API, the deactivation count will be update, and it
> will try to connect or disconnect gadget. It can be used to
> enable functions for gadget when necessary.
>
> Signed-off-by: Peter Chen <peter.chen@xxxxxxxxxxxxx>
> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/usb/gadget/udc/udc-core.c | 35 ++++++++++++++++++++++++++++++++++-
> include/linux/usb/gadget.h | 5 +++++
> 2 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
> index 9396a86..a757334 100644
> --- a/drivers/usb/gadget/udc/udc-core.c
> +++ b/drivers/usb/gadget/udc/udc-core.c
> @@ -37,6 +37,7 @@
> * @list - for use by the udc class driver
> * @vbus - for udcs who care about vbus status, this value is real vbus status;
> * for udcs who do not care about vbus status, this value is always true
> + * @deactivations - the deactivation count to connect or disconnect gadget
> *
> * This represents the internal data structure which is used by the UDC-class
> * to hold information about udc driver and gadget together.
> @@ -47,6 +48,7 @@ struct usb_udc {
> struct device dev;
> struct list_head list;
> bool vbus;
> + int deactivations;
> };
>
> static struct class *udc_class;
> @@ -168,13 +170,44 @@ EXPORT_SYMBOL_GPL(usb_gadget_set_state);
>
> static void usb_udc_connect_control(struct usb_udc *udc)
> {
> - if (udc->vbus)
> + if (udc->vbus && !udc->deactivations)
> usb_gadget_connect(udc->gadget);
> else
> usb_gadget_disconnect(udc->gadget);
> }
>
> /**
> + * usb_udc_activation_handler - updates udc's deactivation count and
> + * try to connect or disconnect
> + *
> + * @gadget: The gadget which the function is at
> + * @active: the function needs to be active or not
> + *
> + * The composite core or function driver calls it when it
> + * wants to activate or deactivate function.
> + */
> +void usb_udc_activation_handler(struct usb_gadget *gadget, bool active)
> +{
> + struct usb_udc *udc = usb_gadget_find_udc(gadget);
> +
if (!udc)
return;
can make this function slightly easier on the eyes.
> + mutex_lock(&udc_lock);
> + if (udc) {
> + if (active) {
> + if (udc->deactivations == 0) {
> + WARN_ON(1);
> + return;
This returns with the udc_lock locked.
Also, you probably want WARN_ON_ONCE() like so:
if (WARN_ON_ONCE(udc->deactivations)) ...
Also, I don't think you want udc_lock here at all, it looks like its (at
least intended) use is to serialize accesses to udc_list. You could use
an atomic if you want to protect against concurrent (de-)activations,
but then you would still need to synchronize
usb_gadget_connect()/usb_gadget_disconnect() that result from these
activations. I assume that normally these will serialize on gadget
driver's spinlock in pullup(), so it should be all right.
Regards,
--
Alex
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