linux-kernel - Re: [PATCH] usb: udc: add gadget state kobject uevent

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Date:	Thu, 18 Jul 2013 13:08:20 +0300
From:	Felipe Balbi <balbi@...com>
To:	Felipe Balbi <balbi@...com>
CC:	Rong Wang <wr011235813@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Rong.Wang@....com>
Subject: Re: [PATCH] usb: udc: add gadget state kobject uevent

Hi,

On Thu, Jul 18, 2013 at 11:40:41AM +0300, Felipe Balbi wrote:
> > >> >> > The question is since we default GADGET, so the g_mass_storage.ko is
> > >> >> > installed early but connecting to a host PC
> > >> >> > is randomly, But the udev has no idea when a host PC connects our device.
> > >> >> >
> > >> >> > So we consider it's reasonable to let the udev know the GADGET device state.
> > >> >> > Is there any alternative to our question?
> > >> >>
> > >> >> I thought we already export events for gadget device states, have you
> > >> >> looked for them?  I can't dig through the code at the moment, but this
> > >> >> seems like a pretty common issue...
> > >> >>
> > >> >> Felipe, any ideas?
> > >> >
> > >> > we already expose that in sysfs. IIRC udev can act on sysfs changes,
> > >> > no ?
> > >>
> > >> I do not know if udev can polling sysfs file content change. I'll study this.
> > >>
> > >> But the change is triggered by calling usb_gadget_set_state, and I find
> > >> composite framework do not call this. Then we should do this common work
> > >> in every udc driver?
> > >
> > > yes. Only the UDC driver knows when the controller is moving among those
> > > states.
> > 
> > OK. I got that.
> > 
> > But I think it may be more reasonable for the udc driver to maintain a
> > work queue
> > to handle the state change since this operation mostly happen in ISR ?
> 
> And that's the patch I want to test. Adding a workqueue to every single
> UDC will be too much, so I tried to hide it in udc-core.c. I agree with
> you we need to pass the sysfs_notification to a separate workqueue
> though. If you can test the patch below, that would be great.
> 
> commit d32521bd775d48b600e67f23d363d70f71597ffd
> Author: Felipe Balbi <balbi@...com>
> Date:   Wed Jul 17 11:09:49 2013 +0300
> 
>     usb: gadget: udc-core: move sysfs_notify() to a workqueue
>     
>     usb_gadget_set_state() will call sysfs_notify()
>     which might sleep. Some users might want to call
>     usb_gadget_set_state() from the very IRQ handler
>     which actually changes the gadget state.
>     
>     Instead of having every UDC driver add their own
>     workqueue for such a simple notification, we're
>     adding it generically to our struct usb_gadget,
>     so the details are hidden from all UDC drivers.
>     
>     Signed-off-by: Felipe Balbi <balbi@...com>
> 
> diff --git a/drivers/usb/gadget/udc-core.c b/drivers/usb/gadget/udc-core.c
> index ffd8fa5..b0d91b1 100644
> --- a/drivers/usb/gadget/udc-core.c
> +++ b/drivers/usb/gadget/udc-core.c
> @@ -23,6 +23,7 @@
>  #include <linux/list.h>
>  #include <linux/err.h>
>  #include <linux/dma-mapping.h>
> +#include <linux/workqueue.h>
>  
>  #include <linux/usb/ch9.h>
>  #include <linux/usb/gadget.h>
> @@ -101,11 +102,18 @@ EXPORT_SYMBOL_GPL(usb_gadget_unmap_request);
>  
>  /* ------------------------------------------------------------------------- */
>  
> +static void usb_gadget_state_work(struct work_struct *work)
> +{
> +	struct usb_gadget	*gadget = work_to_gadget(work);
> +
> +	sysfs_notify(&gadget->dev.kobj, NULL, "status");
> +}
> +
>  void usb_gadget_set_state(struct usb_gadget *gadget,
>  		enum usb_device_state state)
>  {
>  	gadget->state = state;
> -	sysfs_notify(&gadget->dev.kobj, NULL, "status");
> +	schedule_work(&gadget->work);
>  }
>  EXPORT_SYMBOL_GPL(usb_gadget_set_state);
>  
> @@ -192,6 +200,7 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
>  		goto err1;
>  
>  	dev_set_name(&gadget->dev, "gadget");
> +	INIT_WORK(&gadget->work, usb_gadget_state_work);
>  	gadget->dev.parent = parent;
>  
>  	dma_set_coherent_mask(&gadget->dev, parent->coherent_dma_mask);
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index f1b0dca..942ef5e 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -22,6 +22,7 @@
>  #include <linux/slab.h>
>  #include <linux/scatterlist.h>
>  #include <linux/types.h>
> +#include <linux/workqueue.h>
>  #include <linux/usb/ch9.h>
>  
>  struct usb_ep;
> @@ -475,6 +476,7 @@ struct usb_gadget_ops {
>  
>  /**
>   * struct usb_gadget - represents a usb slave device
> + * @work: (internal use) Workqueue to be used for sysfs_notify()
>   * @ops: Function pointers used to access hardware-specific operations.
>   * @ep0: Endpoint zero, used when reading or writing responses to
>   *	driver setup() requests
> @@ -520,6 +522,7 @@ struct usb_gadget_ops {
>   * device is acting as a B-Peripheral (so is_a_peripheral is false).
>   */
>  struct usb_gadget {
> +	struct work_struct		work;
>  	/* readonly to gadget driver */
>  	const struct usb_gadget_ops	*ops;
>  	struct usb_ep			*ep0;
> @@ -538,6 +541,7 @@ struct usb_gadget {
>  	unsigned			out_epnum;
>  	unsigned			in_epnum;
>  };
> +#define work_to_gadget(w)	(container_of((w), struct usb_gadget, work))
>  
>  static inline void set_gadget_data(struct usb_gadget *gadget, void *data)
>  	{ dev_set_drvdata(&gadget->dev, data); }

nevermind, colleague borrowed me his omap5 board. It's tested, will send
a proper patch now.

-- 
balbi

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