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Date: Thu, 30 Apr 2015 11:08:27 +0200
From: Robert Baldyga <r.baldyga@...sung.com>
To: balbi@...com
Cc: gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org, m.szyprowski@...sung.com,
andrzej.p@...sung.com
Subject: Re: [PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate
functions
On 04/29/2015 05:30 PM, Felipe Balbi wrote:
> On Wed, Apr 29, 2015 at 11:08:06AM +0200, Robert Baldyga wrote:
>> Hi Felipe,
>>
>> On 04/28/2015 06:40 PM, Felipe Balbi wrote:
>>> On Tue, Apr 07, 2015 at 10:31:52AM +0200, Robert Baldyga wrote:
>>>> These functions allows to deactivate gadget to make it not visible to
>>>> host and make it active again when gadget driver is finally ready.
>>>>
>>>> They are needed to fix usb_function_activate() and usb_function_deactivate()
>>>> functions which currently are not working as usb_gadget_connect() is
>>>> called immediately after function bind regardless to previous calls of
>>>> usb_gadget_disconnect() function.
>>>
>>> and that's what needs to be fixed, a long time ago I wrote the patch
>>> below which I never got to finishing:
>>>
>>> commit a23800e2463ae1f4eafa7c0a15bb44afee75994f
>>> Author: Felipe Balbi <balbi@...com>
>>> Date: Thu Jul 26 14:23:44 2012 +0300
>>>
>>> usb: gadget: let gadgets control pullup on their own
>>>
>>> This is useful on gadgets that depend on userland
>>> daemons to function properly. We can delay connection
>>> to the host until userland is ready.
>>>
>>> Signed-off-by: Felipe Balbi <balbi@...com>
>>>
>>> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
>>> index 7c821de8ce3d..790ccf29f2ee 100644
>>> --- a/drivers/usb/gadget/composite.c
>>> +++ b/drivers/usb/gadget/composite.c
>>> @@ -1784,8 +1784,9 @@ int usb_composite_probe(struct usb_composite_driver *driver)
>>> driver->name = "composite";
>>>
>>> driver->gadget_driver = composite_driver_template;
>>> - gadget_driver = &driver->gadget_driver;
>>>
>>> + gadget_driver = &driver->gadget_driver;
>>> + gadget_driver->controls_pullups = driver->controls_pullups;
>>> gadget_driver->function = (char *) driver->name;
>>> gadget_driver->driver.name = driver->name;
>>> gadget_driver->max_speed = driver->max_speed;
>>> diff --git a/drivers/usb/gadget/udc-core.c b/drivers/usb/gadget/udc-core.c
>>> index 8a1eeb24ae6a..c0f4fca9384b 100644
>>> --- a/drivers/usb/gadget/udc-core.c
>>> +++ b/drivers/usb/gadget/udc-core.c
>>> @@ -235,7 +235,18 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
>>>
>>> kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
>>>
>>> - usb_gadget_disconnect(udc->gadget);
>>> + /*
>>> + * NOTICE: if gadget driver wants to control
>>> + * pullup, it needs to make sure that when
>>> + * user tries to rmmod the gadget driver, it
>>> + * will disconnect the pullups before returning
>>> + * from its ->unbind() method.
>>> + *
>>> + * We are truly trusting the gadget driver here.
>>> + */
>>> + if (!udc->driver->controls_pullups)
>>> + usb_gadget_disconnect(udc->gadget);
>>> +
>>> udc->driver->disconnect(udc->gadget);
>>> udc->driver->unbind(udc->gadget);
>>> usb_gadget_udc_stop(udc->gadget, udc->driver);
>>> @@ -300,7 +311,18 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri
>>> driver->unbind(udc->gadget);
>>> goto err1;
>>> }
>>> - usb_gadget_connect(udc->gadget);
>>> +
>>> + /*
>>> + * NOTICE: if gadget driver wants to control
>>> + * pullups, it needs to make sure its calls
>>> + * to usb_function_activate() and
>>> + * usb_function_deactivate() are balanced,
>>> + * otherwise gadget_driver will never enumerate.
>>> + *
>>> + * We are truly trusting the gadget driver here.
>>> + */
>>> + if (!driver->controls_pullups)
>>> + usb_gadget_connect(udc->gadget);
>>>
>>> kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
>>> return 0;
>>> diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
>>> index 3c671c1b37f6..7ae797c85cb9 100644
>>> --- a/include/linux/usb/composite.h
>>> +++ b/include/linux/usb/composite.h
>>> @@ -157,6 +157,7 @@ struct usb_function {
>>> int (*get_status)(struct usb_function *);
>>> int (*func_suspend)(struct usb_function *,
>>> u8 suspend_opt);
>>> +
>>> /* private: */
>>> /* internals */
>>> struct list_head list;
>>> @@ -279,6 +280,8 @@ enum {
>>> * @max_speed: Highest speed the driver supports.
>>> * @needs_serial: set to 1 if the gadget needs userspace to provide
>>> * a serial number. If one is not provided, warning will be printed.
>>> + * @controls_pullups: this driver will control pullup and udc-core shouldn't
>>> + * enable it by default
>>> * @bind: (REQUIRED) Used to allocate resources that are shared across the
>>> * whole device, such as string IDs, and add its configurations using
>>> * @usb_add_config(). This may fail by returning a negative errno
>>> @@ -308,6 +311,7 @@ struct usb_composite_driver {
>>> struct usb_gadget_strings **strings;
>>> enum usb_device_speed max_speed;
>>> unsigned needs_serial:1;
>>> + unsigned controls_pullups:1;
>>>
>>> int (*bind)(struct usb_composite_dev *cdev);
>>> int (*unbind)(struct usb_composite_dev *);
>>> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
>>> index 32b734d88d6b..87971fa38f08 100644
>>> --- a/include/linux/usb/gadget.h
>>> +++ b/include/linux/usb/gadget.h
>>> @@ -774,6 +774,7 @@ static inline int usb_gadget_disconnect(struct usb_gadget *gadget)
>>> * @suspend: Invoked on USB suspend. May be called in_interrupt.
>>> * @resume: Invoked on USB resume. May be called in_interrupt.
>>> * @driver: Driver model state for this driver.
>>> + * @controls_pullups: tells udc-core to not enable pullups by default
>>> *
>>> * Devices are disabled till a gadget driver successfully bind()s, which
>>> * means the driver will handle setup() requests needed to enumerate (and
>>> @@ -833,6 +834,8 @@ struct usb_gadget_driver {
>>>
>>> /* FIXME support safe rmmod */
>>> struct device_driver driver;
>>> +
>>> + unsigned controls_pullups:1;
>>> };
>>>
>>>
>>>
>>> Together with that, I wrote:
>>>
>>> commit 0b733885e276a38cc9fa415c0977f063f9ce4d9d
>>> Author: Felipe Balbi <balbi@...com>
>>> Date: Wed Feb 6 12:34:33 2013 +0200
>>>
>>> usb: gadget: webcam: let it control pullups
>>>
>>> this gadget driver needs to make sure that
>>> we will only enumerate after its userland
>>> counterpart is up and running.
>>>
>>> Signed-off-by: Felipe Balbi <balbi@...com>
>>>
>>> diff --git a/drivers/usb/gadget/webcam.c b/drivers/usb/gadget/webcam.c
>>> index 8cef1e658c29..41a4d03715bc 100644
>>> --- a/drivers/usb/gadget/webcam.c
>>> +++ b/drivers/usb/gadget/webcam.c
>>> @@ -388,6 +388,7 @@ static __refdata struct usb_composite_driver webcam_driver = {
>>> .max_speed = USB_SPEED_SUPER,
>>> .bind = webcam_bind,
>>> .unbind = webcam_unbind,
>>> + .controls_pullups = true,
>>> };
>>>
>>> static int __init
>>>
>>> This makes it really simple, either a gadget driver wants to control
>>> pullups, or it doesn't. For those who wish to control pullups (for
>>> whatever reason) we rely completely on the gadget telling us it's ok to
>>> connect pullups by means of usb_function_activate()/deactivate(), for
>>> all others, we just connect straight away.
>>>
>>
>> It looks like your patch fixes problem at gadget level, but in case of
>> gadgets composed using ConfigFS we don't know if any function will want
>> to deactivate gadget. We would need to supply mechanism which functions
>> could use to tell composite that they want to control pullups by
>> themselves. That's why I made it a little more complicated, but in
>> result we have no need to modify function drivers.
>
> I really prefer functions to tell us that they can control pullups; much
> like Host stack requires a "supports_autosuspend" flag if your driver
> supports runtime PM.
>
> I see that your patch is much more granular, but then, we need a
> per-function flag then we could:
>
> for_each_function(config)
> if (fuction->controls_pullup)
> usb_function_deactivate(function);
>
> (well, just illustrating)
>
> Then, usb_function_deactivate() is initially called by the framework so
> that deactivate counter already has the correct initial value and gadget
> will only connect after all functions in a particular configuration have
> called usb_function_activate(). How do you feel about that ?
Looks good to me, makes things more clear. I will update my patches.
Thanks,
Robert Baldyga
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