diff options
author | Alan Stern <stern@rowland.harvard.edu> | 2021-05-20 16:21:44 -0400 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-06-04 13:51:55 +0200 |
commit | 7dc0c55e9f302e7048e040ee4437437bbea1e2cd (patch) | |
tree | bca9d832381c3894abd5e56121c382820ec0266b /drivers/usb/gadget/udc/core.c | |
parent | ab1150e9576f5889107568329ebc62902ed83682 (diff) |
USB: UDC core: Add udc_async_callbacks gadget op
The Gadget API has a theoretical race when a gadget driver is unbound.
Although the pull-up is turned off before the driver's ->unbind
callback runs, if the USB cable were to be unplugged at just the wrong
moment there would be nothing to prevent the UDC driver from invoking
the ->disconnect callback after the unbind has finished. In theory,
other asynchronous callbacks could also happen during the time before
the UDC driver's udc_stop routine is called, and the gadget driver
would not be prepared to handle any of them.
We need a way to tell UDC drivers to stop issuing asynchronous (that is,
->suspend, ->resume, ->disconnect, ->reset, or ->setup) callbacks at
some point after the pull-up has been turned off and before the
->unbind callback runs. This patch adds a new ->udc_async_callbacks
callback to the usb_gadget_ops structure for precisely this purpose,
and it adds the corresponding support to the UDC core.
Later patches in this series add support for udc_async_callbacks to
several UDC drivers.
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20210520202144.GC1216852@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/gadget/udc/core.c')
-rw-r--r-- | drivers/usb/gadget/udc/core.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c index 493ff93f7dda..b7f0b1ebaaa8 100644 --- a/drivers/usb/gadget/udc/core.c +++ b/drivers/usb/gadget/udc/core.c @@ -1148,6 +1148,53 @@ static inline void usb_gadget_udc_set_speed(struct usb_udc *udc, } /** + * usb_gadget_enable_async_callbacks - tell usb device controller to enable asynchronous callbacks + * @udc: The UDC which should enable async callbacks + * + * This routine is used when binding gadget drivers. It undoes the effect + * of usb_gadget_disable_async_callbacks(); the UDC driver should enable IRQs + * (if necessary) and resume issuing callbacks. + * + * This routine will always be called in process context. + */ +static inline void usb_gadget_enable_async_callbacks(struct usb_udc *udc) +{ + struct usb_gadget *gadget = udc->gadget; + + if (gadget->ops->udc_async_callbacks) + gadget->ops->udc_async_callbacks(gadget, true); +} + +/** + * usb_gadget_disable_async_callbacks - tell usb device controller to disable asynchronous callbacks + * @udc: The UDC which should disable async callbacks + * + * This routine is used when unbinding gadget drivers. It prevents a race: + * The UDC driver doesn't know when the gadget driver's ->unbind callback + * runs, so unless it is told to disable asynchronous callbacks, it might + * issue a callback (such as ->disconnect) after the unbind has completed. + * + * After this function runs, the UDC driver must suppress all ->suspend, + * ->resume, ->disconnect, ->reset, and ->setup callbacks to the gadget driver + * until async callbacks are again enabled. A simple-minded but effective + * way to accomplish this is to tell the UDC hardware not to generate any + * more IRQs. + * + * Request completion callbacks must still be issued. However, it's okay + * to defer them until the request is cancelled, since the pull-up will be + * turned off during the time period when async callbacks are disabled. + * + * This routine will always be called in process context. + */ +static inline void usb_gadget_disable_async_callbacks(struct usb_udc *udc) +{ + struct usb_gadget *gadget = udc->gadget; + + if (gadget->ops->udc_async_callbacks) + gadget->ops->udc_async_callbacks(gadget, false); +} + +/** * usb_udc_release - release the usb_udc struct * @dev: the dev member within usb_udc * @@ -1361,6 +1408,7 @@ static void usb_gadget_remove_driver(struct usb_udc *udc) kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE); usb_gadget_disconnect(udc->gadget); + usb_gadget_disable_async_callbacks(udc); if (udc->gadget->irq) synchronize_irq(udc->gadget->irq); udc->driver->unbind(udc->gadget); @@ -1442,6 +1490,7 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri driver->unbind(udc->gadget); goto err1; } + usb_gadget_enable_async_callbacks(udc); usb_udc_connect_control(udc); kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE); |