[PATCH 0/2] usb: gadget: Fix gadget deactivaton feature

[PATCH 0/2] usb: gadget: Fix gadget deactivaton feature

[Robert Baldyga]

Hi,

This patch set introduces two functions usb_gadget_deactivate() and
usb_gadget_activate(), designed to prevent udc-core from showing binded
gadget to host until it will be ready to work. It also makes
usb_function_deactivate()/activate() using these functions.

So far gadget deactivation was made by calling usb_gadget_disconnect(),
but since we have usb_gadget_connect() called after gadget->bind()
(in udc_bind_to_driver()) this method doesn't provide expected result.
Calling function usb_gadget_disconnect() before gadget connection doesn't
prevent udc-core from connecting gadget to driver - usb_gadget_disconnect()
call is ignored and gadget is connected regardless to it. This usually
results with errors, for example because we binded gadget with 0
configurations.

This patch set fixes this problem adding functions allowing to perform
effective gadget deactivation from gadget->bind().

Best regards,
Robert Baldyga

Robert Baldyga (2):
  usb: gadget: add usb_gadget_activate/deactivate functions
  usb: composite: fix usb_function_activate/deactivate functions

 drivers/usb/gadget/composite.c |   4 +-
 include/linux/usb/gadget.h     | 100 ++++++++++++++++++++++++++++++++++++++---
 2 files changed, 96 insertions(+), 8 deletions(-)

-- 
1.9.1

[PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate functions

[Robert Baldyga]

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.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
---
 include/linux/usb/gadget.h | 100 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 94 insertions(+), 6 deletions(-)

diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 4f3dfb7..15604bb 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -526,6 +526,9 @@ struct usb_gadget_ops {
  * @quirk_ep_out_aligned_size: epout requires buffer size to be aligned to
  *	MaxPacketSize.
  * @is_selfpowered: if the gadget is self-powered.
+ * @deactivated: True if gadget is deactivated - in deactivated state it cannot
+ *	be connected.
+ * @connected: True if gadget is connected.
  *
  * Gadgets have a mostly-portable "gadget driver" implementing device
  * functions, handling all usb configurations and interfaces.  Gadget
@@ -568,6 +571,8 @@ struct usb_gadget {
 	unsigned			a_alt_hnp_support:1;
 	unsigned			quirk_ep_out_aligned_size:1;
 	unsigned			is_selfpowered:1;
+	unsigned			deactivated:1;
+	unsigned			connected:1;
 };
 #define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
 
@@ -771,9 +776,24 @@ static inline int usb_gadget_vbus_disconnect(struct usb_gadget *gadget)
  */
 static inline int usb_gadget_connect(struct usb_gadget *gadget)
 {
+	int ret;
+
 	if (!gadget->ops->pullup)
 		return -EOPNOTSUPP;
-	return gadget->ops->pullup(gadget, 1);
+
+	if (gadget->deactivated) {
+		/*
+		 * If gadget is deactivated we only save new state.
+		 * Gadget will be connected automatically after activation.
+		 */
+		gadget->connected = true;
+		return 0;
+	}
+
+	ret = gadget->ops->pullup(gadget, 1);
+	if (!ret)
+		gadget->connected = 1;
+	return ret;
 }
 
 /**
@@ -784,20 +804,88 @@ static inline int usb_gadget_connect(struct usb_gadget *gadget)
  * as a disconnect (when a VBUS session is active).  Not all systems
  * support software pullup controls.
  *
+ * Returns zero on success, else negative errno.
+ */
+static inline int usb_gadget_disconnect(struct usb_gadget *gadget)
+{
+	int ret;
+
+	if (!gadget->ops->pullup)
+		return -EOPNOTSUPP;
+
+	if (gadget->deactivated) {
+		/*
+		 * If gadget is deactivated we only save new state.
+		 * Gadget will stay disconnected after activation.
+		 */
+		gadget->connected = false;
+		return 0;
+	}
+
+	ret = gadget->ops->pullup(gadget, 0);
+	if (!ret)
+		gadget->connected = 0;
+	return ret;
+}
+
+/**
+ * usb_gadget_deactivate - deactivate function which is not ready to work
+ * @gadget: the peripheral being deactivated
+ *
  * This routine may be used during the gadget driver bind() call to prevent
  * the peripheral from ever being visible to the USB host, unless later
- * usb_gadget_connect() is called.  For example, user mode components may
+ * usb_gadget_activate() is called.  For example, user mode components may
  * need to be activated before the system can talk to hosts.
  *
  * Returns zero on success, else negative errno.
  */
-static inline int usb_gadget_disconnect(struct usb_gadget *gadget)
+static inline int usb_gadget_deactivate(struct usb_gadget *gadget)
 {
-	if (!gadget->ops->pullup)
-		return -EOPNOTSUPP;
-	return gadget->ops->pullup(gadget, 0);
+	int ret;
+
+	if (gadget->deactivated)
+		return 0;
+
+	if (gadget->connected) {
+		ret = usb_gadget_disconnect(gadget);
+		if (ret)
+			return ret;
+		/*
+		 * If gadget was being connected before deactivation, we want
+		 * to reconnect it in usb_gadget_activate().
+		 */
+		gadget->connected = true;
+	}
+	gadget->deactivated = true;
+
+	return 0;
 }
 
+/**
+ * usb_gadget_activate - activate function which is not ready to work
+ * @gadget: the peripheral being activated
+ *
+ * This routine activates gadget which was previously deactivated with
+ * usb_gadget_deactivate() call. It calls usb_gadget_connect() if needed.
+ *
+ * Returns zero on success, else negative errno.
+ */
+static inline int usb_gadget_activate(struct usb_gadget *gadget)
+{
+	if (!gadget->deactivated)
+		return 0;
+
+	gadget->deactivated = false;
+
+	/*
+	 * If gadget has been connected before deactivation, or became connected
+	 * while it was being deactivated, we call usb_gadget_connect().
+	 */
+	if (gadget->connected)
+		return usb_gadget_connect(gadget);
+
+	return 0;
+}
 
 /*-------------------------------------------------------------------------*/
 
-- 
1.9.1

[PATCH 2/2] usb: composite: fix usb_function_activate/deactivate functions

[Robert Baldyga]

Using usb_gadget_disconnect to make gadget temporarily invisible to host
doesn't provide desired result, because gadget is connected immediately
after binding regardless to previous usb_gadget_disconnect() calls.

For this reason we use usb_gadget_deactivate() instead of
usb_gadget_disconnect() to make it working as expected.

Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
---
 drivers/usb/gadget/composite.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 4e3447b..9ed77f4 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -279,7 +279,7 @@ int usb_function_deactivate(struct usb_function *function)
 	spin_lock_irqsave(&cdev->lock, flags);
 
 	if (cdev->deactivations == 0)
-		status = usb_gadget_disconnect(cdev->gadget);
+		status = usb_gadget_deactivate(cdev->gadget);
 	if (status == 0)
 		cdev->deactivations++;
 
@@ -311,7 +311,7 @@ int usb_function_activate(struct usb_function *function)
 	else {
 		cdev->deactivations--;
 		if (cdev->deactivations == 0)
-			status = usb_gadget_connect(cdev->gadget);
+			status = usb_gadget_activate(cdev->gadget);
 	}
 
 	spin_unlock_irqrestore(&cdev->lock, flags);
-- 
1.9.1

Re: [PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate functions

[Felipe Balbi]

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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@ti.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@ti.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@ti.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@ti.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.

cheers

-- 
balbi

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Re: [PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate functions

[Robert Baldyga]

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@ti.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@ti.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@ti.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@ti.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.

Thanks,
Robert Baldyga

Re: [PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate functions

[Felipe Balbi]

[-- Attachment #1: Type: text/plain, Size: 8317 bytes --]

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@ti.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@ti.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@ti.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@ti.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 ?

-- 
balbi

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Re: [PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate functions

[Robert Baldyga]

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@ti.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@ti.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@ti.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@ti.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

Re: [PATCH 1/2] usb: gadget: add usb_gadget_activate/deactivate functions

[Felipe Balbi]

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On Thu, Apr 30, 2015 at 11:08:27AM +0200, Robert Baldyga wrote:
> 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@ti.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@ti.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@ti.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@ti.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.

Cool, thanks

Let's see what you come up with for configuration changes, I didn't
think too much about it, but we need to consider that possibility too.

-- 
balbi

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